Category Archives: Telescopes

Massive Black Hole Could Challenge Stellar Evolution Theories

Astronomers have used the Very Long Baseline Array (VLBA) to discover that the first black hole ever detected is actually much larger than previously believed. So large, at 21 times the mass of the Sun, that it challenges existing theories about the evolution of stars and how they form black holes. These constraints should limit stellar black holes in binary systems to about 15 solar masses.

Cygnus X-1 is a Milky Way binary system that contains a black hole and a supergiant companion star feeding it gas and other material. First discovered in 1964, the binary system has gone on to become one of the most intensely studied objects in astronomy. Yet, our familiarity with Cygnus X-1 doesn’t mean it can’t still deliver a surprise or two.

An artist’s impression of the Cygnus X-1 system. A stellar-mass black hole orbits with a
companion star located 7,200 light-years from Earth. (ICRAR)

In addition to finding the black hole is 50% more massive than prior estimates, near 21 solar masses as opposed to 15 solar masses, the team also discovered that the companion star also has a greater mass than previous measurements had revealed. The system as a whole is 20% further away than previously calculated–7,200 light-years from Earth as opposed to 6,100 light-years.

“We know that Cygnus X-1 hosts a black hole that is 21 times the mass of the Sun. We also learned that the supergiant companion star in Cygnus X-1 is also more massive than we had thought, with a mass of about 40 times the mass of the Sun,” Professor James Miller-Jones, the International Centre for Radio Astronomy Research (ICRAR), Curtin University, Australia, tells ZME Science. “The revised masses and distances also lead to an updated orbital separation between the star and the black hole — they orbit each other at a separation of one-quarter the distance from the Earth to the Sun.”

Cygnus X-1: New findings show the binary system is more massive and further away than previous estimates implied. (ICRAR)

The finding, published in the latest edition of the journal Science, means that Cygnus X-1 contains the largest black hole created through the collapse of a star alone, that has ever been detected with traditional electromagnetic astronomy without the use of gravitational waves. Larger black holes do of course exist, but these are formed through other mechanisms such as mergers between smaller black holes after that initial stellar collapse.

Miller-Jones, the study’s lead researcher, goes on to explain that the team also learned that the black hole is spinning very rapidly , close to its maximum possible speed. 

“With all this new information, we were able to propose a likely scenario for how this system formed, which can explain its observed properties.”

Professor James Miller-Jones, ICRAR, Curtin University

The finding doesn’t conform to current theories about black hole formation and stellar development in binary systems as its mass is greater than the limit imposed on such an object. 

How Cygnus X-1 Challenges Theories of Stellar Evolution

The team chanced on their finding whilst conducting an ambitious project to observe Cygnus X-1 almost continuously over a full 5.6-day orbit with the network of radio telescopes that comprise VLBA and X-ray telescopes. The aim of the research was to better understand how gas being fed into a black hole from a binary partner via a spiraling accretion disc connects to powerful jets of material that launch out from near the central region at near light speed.

“We had not originally aimed to refine the distance and the mass of the black hole but realised that our data would allow us to do so, by accounting properly for the effects of the black hole orbit.  But there is still a wealth of data from this rich observing campaign that we are looking to analyse more fully.”

Professor James Miller-Jones, ICRAR, Curtin University

“Black holes form from the deaths of the most massive stars when they run out of fuel and gravity takes over,” says Miller-Jones. “The mass of the resulting black hole is set by the initial mass of the star from which it formed — which we call the progenitor star — the amount of mass that star lost in winds over its lifetime, and any interactions with a nearby companion star.” 

Miller-Jones continues, saying massive stars launch very powerful winds from their surfaces, which leads to significant mass loss over their few-million year lifetimes. Some of the later phases of star’s evolution have particularly strong winds — determined by the abundance of elements heavier than helium in the gas from which the star was formed. More heavy elements mean stronger winds, and ultimately, a less massive star immediately before gravitational collapse. 

While some stars can also lose further mass in supernova explosions as they collapse to form a black hole, the evidence suggests that in Cygnus X-1, there was no explosion, and the star collapsed directly into a black hole,” says Miller-Jones. “The stronger the stellar winds during the late evolutionary phases of the star, the less massive we would have expected the black hole to be.”

An artist’s impression of the Cygnus X-1 system. This system contains the most massive stellar-mass black hole ever detected without the use of gravitational waves, weighing in at 21 times the mass of the Sun. (ICRAR)

At first, the team wasn’t totally aware of just how significant their discovery of mass disparities in the Cygnus X-1 binary system was. “I think that our biggest surprise was when we appreciated the full implications of our measurements,” Miller-Jones says. “As observational astronomers, my team and I had already found that we could revise the source distance and the black hole mass. However, it was not until I visited a colleague, Professor Ilya Mandel of Monash University, who is a theoretical astronomer, that we realised how important this actually was.”

Mandel–co-author on the resulting paper– realised that a 21-solar mass black hole was too massive to form in the Milky Way with the constraints in place due to the current prevailing estimates of the amount of mass lost by massive stars in stellar winds.

“The existence of such a massive black hole in our own Milky Way galaxy has shown us that the most massive stars blow less mass off their surface in winds than we had previously estimated. This improves our knowledge of how black holes form from the most massive stars.”

Professor James Miller-Jones, ICRAR, Curtin University

Cygnus X-1: No Stranger to Contraversy

The team’s findings have allowed them to put forward a scenario that would allow the formation of a 21 solar mass black hole in a binary system. “We suggest that the star that eventually collapsed into a black hole began its life a few million years ago with a mass of 55-75 times the mass of the Sun,” Miller-Jones tells ZME.  “Over its lifetime, it was close enough to its companion–the current supergiant–that gas from its surface was transferred onto its companion.  This removed the outer layers of the black hole progenitor and caused it to rotate more rapidly because the two stars were always keeping the same face towards one another. 

“Eventually, possibly as recently as a few tens of thousands of years ago the progenitor star collapsed directly into a black hole–of close to its current mass of 21 times the mass of the Sun–without a supernova explosion.”

Professor James Miller-Jones, ICRAR, Curtin University



Additionally, as well as gaining an insight into the black hole’s birth, Miller-Jones believes the team’s results could also indicate how the system could end its life. “Finally, we considered the eventual fate of this system,” the paper’s lead author says. “While the current companion star may eventually form a black hole, the separation of the two stars is such that the two black holes are unlikely to merge on a timescale comparable to the age of the Universe.”   

A companion paper appearing at the same time in the Astrophysical Journal will delve deeper into these elements of the research.

A closer look at the massive star in the Cygnus X-1 binary (ICRAR)

This isn’t the first time that Cygnus X-1, and more specifically its black hole, has sparked discussion in the fields of astronomy and cosmology. As speculation grew during that the intense X-ray source in the region was the result of a black hole, renowned physicist Stephen Hawking bet fellow scientist Kip Thorne–well known for his black hole work–in 1974 that Cygnus X-1 did not contain a black hole.

“This was a form of insurance policy for me. I have done a lot of work on black holes, and it would all be wasted if it turned out that black holes do not exist. But in that case, I would have the consolation of winning my bet, which would win me four years of the magazine Private Eye. If black holes do exist, Kip will get one year of Penthouse.”

Stephen Hawking, A Brief History of Time

Hawking lost the bet, conceding by breaking into Thorne’s office whilst he was on a trip to Russia and signing the framed bet.

The team now intend to apply the technique that led them to this finding to investigate further black holes. This should enable them to better understand how massive stars lose mass through stellar winds. With that said, as Cygnus X-1 is relatively unique in the Milky Way–as one of the few black holes so far detected in orbit with a massive companion star– Miller-Jones believes that they are unlikely to find any more binary systems in which the masses of the constituent star and black hole diverge so drastically from current estimates.

“Most excitingly for me, the advent of cutting-edge new telescopes such as the Square Kilometre Array radio telescope (SKA) will allow us to detect many more black holes, and study their properties, including how matter flows into and away from them, in more detail than ever before,” concludes Professor Miller-Jones. “It’s an exciting time to be in this field!”

Sources

Miller-Jones. J., Orosz. J. A., Mandel. I., ‘Cygnus X-1 contains a 21-solar mass black hole – implications for massive star winds,’ Science, [2021], [https://science.sciencemag.org/lookup/doi/10.1126/science.abb3363]

This artist’s impression shows the view from the planet in the TOI-178 system found orbiting furthest from the star. New research by Adrien Leleu and his colleagues with several telescopes, including ESO’s Very Large Telescope, has revealed that the system boasts six exoplanets and that all but the one closest to the star are locked in a rare rhythm as they move in their orbits.  But while the orbital motion in this system is in harmony, the physical properties of the planets are more disorderly, with significant variations in density from planet to planet. This contrast challenges astronomers’ understanding of how planets form and evolve. This artist’s impression is based on the known physical parameters for the planets and the star seen, and uses a vast database of objects in the Universe. (ESO/L. Calçada/spaceengine.org)

Astronomers discover an exoplanet system with rhythm

Astronomers have discovered a unique system of exoplanets in which all but one of the planets orbit their parent star in a rare rhythm. The finding could force us to revise our ideas of how planets–including those in our own solar system–form.

The team–including astronomers from the University of Bern and the University of Geneva–used a combination of telescopes and the European Southern Observatory’s (ESO) Very Large Telescope (VLT) to observe the star TOI-178, 200 light-years away from us in the constellation Sculptor.

This artist’s impression shows the view from the planet in the TOI-178 system found orbiting furthest from the star. New research by Adrien Leleu and his colleagues with several telescopes, including ESO’s Very Large Telescope, has revealed that the system boasts six exoplanets and that all but the one closest to the star are locked in a rare rhythm as they move in their orbits.  But while the orbital motion in this system is in harmony, the physical properties of the planets are more disorderly, with significant variations in density from planet to planet. This contrast challenges astronomers’ understanding of how planets form and evolve. This artist’s impression is based on the known physical parameters for the planets and the star seen, and uses a vast database of objects in the Universe. (ESO/L. Calçada/spaceengine.org)
This artist’s impression shows the view from the planet in the TOI-178 system found orbiting furthest from the star based on the known physical parameters for the planets and the star as seen and using a vast database of objects in the Universe. (ESO/L. Calçada/spaceengine.org)

Upon first glance, the astronomers believed that the star was orbited by just two exoplanets, both of which had the same orbits. Closer inspection revealed something surprising, however — six planets, five of which are locked in a rhythmic dance with each other.

“Through further observations, we realised that there were not two planets orbiting the star at roughly the same distance from it, but rather multiple planets in a very special configuration,” says lead researcher Adrien Leleu, University of Bern.

This rhythm reveals a star system that has remained undisturbed by cosmic events since its birth. But, even within this system exists a measure of chaos, with the compositions of the constituent planets displaying some disharmonious densities that are just as rare as their harmonious orbits.

The system consists of planets ranging from one to three times the size of Earth, with masses that range from 1.5 to 30 times that of our planet. Some are rocky and larger than Earth–so-called Super-Earths. Others are gaseous like the solar system’s outer bodies, but much smaller–a class of exoplanets called Mini Neptunes.

“This contrast between the rhythmic harmony of the orbital motion and the disorderly densities certainly challenges our understanding of the formation and evolution of planetary systems,” Leleu adds.

The team’s research is published in the journal  Astronomy & Astrophysics.

This animation shows a representation of the orbits and movements of the planets in the TOI-178 system. In this artist’s animation, the rhythmic movement of the planets around the central star is represented through a musical harmony, created by attributing a note (in the pentatonic scale) to each of the planets in the resonance chain. This note plays when a planet completes either one full orbit or one-half orbit; when planets align at these points in their orbits, they ring in resonance. (ESO/L. Calçada)

Exoplanets in Resonance

All the exoplanets around TOI-178, barring the one closest to the star itself, are exhibiting a resonance can be observed in the repeated patterns in their orbits. These repeating orbits mean that the planets align at regular intervals as they loop their parent star.

A similar–albeit less complex– resonance can be found in our own solar system, not with planets, but with three of the moons of Jupiter. Io completes four full orbits for every orbit of Ganymede, whilst also completing two full orbits for every orbit of Europa. This is what is known as a 4:2:1 resonance.

TOI-178’s five outer planets possess a far more complex chain of resonance than these moons, however. The exoplanets exist in an 18:9:6:4:3 resonance. This means the first exoplanet in the chain–the second closest to the star overall–completes 18 orbits as the second in the chain completes nine, the third completes six, and the fourth completes 4, and the fifth (the sixth planet overall) completes three orbits.

This artist’s animation shows the view from the planet in the TOI-178 system found orbiting furthest from the star, with the inner planets visible in the background. This animation is based on the known physical parameters for the planets and the star seen, and uses a vast database of objects in the Universe. (
ESO/L. Calçada/spaceengine.org)

The team were able to take the resonance of the four planets described above and use it to discover the fifth in the chain, which is the sixth and final planet overall.

The team believes that the exoplanet’s rhythmic orbits could teach them more the system than its current state, though. It could even provide them with a window into its past. “The orbits in this system are very well ordered, which tells us that this system has evolved quite gently since its birth,” explains co-author Yann Alibert from the University of Bern.

In fact, the resonance of the system shows that it has remained relatively undisturbed since its formation. Were it to have been significantly disturbed earlier in its life–by a giant impact or the gravitational influence of another system, for example– the fragile configuration of its orbits would have been obliterated.

Disharmony and Disorder Enter the Picture

It’s not all harmony within the TOI-178 exoplanets., however. Whilst their arrangements and neat and well-ordered, the densities and compositions of the individual exoplanets are much more disordered. It’s a disorder that is very different from what we observe in our solar system.

“It appears there is a planet as dense as the Earth right next to a very fluffy planet with half the density of Neptune, followed by a planet with the density of Neptune. It is not what we are used to,” team member Nathan Hara, University of Geneva, says, describing a system comprised of Super Earths and Mini Neptunes.

As is the case with most exoplanets, the planets in the TOI-178 system were difficult to spot. The team used data collected by the European Space Agency’s CHEOPS satellite, launched in December 2019, with instruments at the VLT located in Chile’s Atacama Desert region.

The astronomers used the transit method that measures tiny dips in light to spot the exoplanets (NASA)

In addition to this data, the team used two of the most common techniques used by astronomers to spot exoplanets. Examing the light emitted by a parent star and how it dips indicates when a planet is transitting in front of it. Also, orbits of exoplanets around a parent star can cause it to ‘wobble’–something that can be seen in its light profile.

This combination of methods allowed the team to discover that the exoplanets in TOI-178 are orbiting their parent star far more rapidly and at a much closer distance than Earth orbits the Sun.

The innermost planet, the one not part of the resonant chain, is the fastest and orbits TOI-178 in just a matter of days. The slowest has an orbit that takes ten times this period to complete.

None of the planets seems to be orbiting in what is believed to be TOI-178’s habitable zone–the area in which water can exist as a liquid. But, the team believes that studying the resonance chain could uncover additional planets in this system, some with orbits that bring them within this region.–also colourfully nicknamed the ‘Goldilocks zone’ because it is neither too hot not too cold.

The researchers will continue to investigate this unique and extraordinary system and suggest that it could be a target for intense observation with the ESO’s Extremely Large Telescope (ELT) when it begins operations later this decade.

The ELT should be able to allow researchers to directly image the exoplanets in Goldilocks zones around stars like TOI-178 as well as study their atmospheres in detail.

This could reveal that the TOI-178 holds even more secrets than this study has revealled.

Original Research

A. Leleu, Y. Alibert, N. C. Hara, et al, ‘Six transiting planets and a chain of Laplace resonances in TOI-178,’ Astronomy & Astrophysics, [2021], (doi: 10.1051/0004-6361/202039767).

An artist’s view of the TRAPPIST-1 system. The TRAPPIST-1 star is home to the largest batch of roughly Earth-size planets ever found outside our solar system. An international study involving researchers from the Universities of Bern, Geneva and Zurich now shows that the exoplanets have remarkably similar densities, which provides clues about their composition (NASA/JPL-Caltech)

The Trappist-1 exoplanets could be worlds of water or rust

The star system of Trappist-1 is home to the largest group of Earth-like planets ever discovered elsewhere in the Universe by astronomers. This means that investigating these seven rocky worlds gives us a good idea of how common exoplanets with similar compositions to our own are in the Milky Way and the wider cosmos.

New research has revealed that these planets, which orbit the Trappist-1 star 40 light-years away from Earth, all have remarkably similar compositions and densities. Yet, all are less dense than Earth.

The results could indicate these are worlds with much more water than is found on earth, or possibly even that these planets are composed almost entirely of rust.

An artist’s view of the TRAPPIST-1 system. The TRAPPIST-1 star is home to the largest batch of roughly Earth-size planets ever found outside our solar system. An international study involving researchers from the Universities of Bern, Geneva and Zurich now shows that the exoplanets have remarkably similar densities, which provides clues about their composition (NASA/JPL-Caltech)
An artist’s view of the TRAPPIST-1 system. The TRAPPIST-1 star is home to the largest batch of roughly Earth-size planets ever found outside our solar system. An international study involving researchers from the Universities of Bern, Geneva and Zurich now shows that the exoplanets have remarkably similar densities, which provides clues about their composition (NASA/JPL-Caltech)


This similarity between the exoplanets makes the Trappist-1 system significantly different from our own solar system which consists of planets with radically compositions and densities. Trappist-1’s worlds are dense, meaning they are like the rocky planets in our solar system, Earth, Mars, Venus, and Mercury. The system seems to be lacking larger gas dominated planets like Jupiter, Saturn, Uranus and Neptune.

The finding, documented in a paper published in the Planetary science Journal shows how the system, first discovered in 2016, offers insight into the wide variety of planetary systems that could fill the Universe.

This chart shows, on the top row, artist concepts of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii, masses, densities and surface gravity as compared to those of Earth. On the bottom row, the same numbers are displayed for the bodies of our inner solar system: Mercury, Venus, Earth and Mars. (NASA/ JPL - Caltech)
This chart shows, on the top row, artist concepts of the seven planets of TRAPPIST-1 with their orbital periods, distances from their star, radii, masses, densities and surface gravity as compared to those of Earth. On the bottom row, the same numbers are displayed for the bodies of our inner solar system: Mercury, Venus, Earth and Mars. (NASA/ JPL – Caltech)

“The new observations allowed us to use transit data from a much longer time span than was available to us for the 2018 calculations,” explains Simon Grimm of the University of Bern, who as well as being involved in the current study, was part of a 2018 team that provided the most accurate calculation of the masses of the seven planets thus far. “With the new data, we were able to refine the mass and density determinations of all seven planets.

“It turned out that the derived densities of the planets are even more similar than we had previously expected.”

Seven Exoplanets with Similar Densities

The similarity in densities observed in the Trappist-1 exoplanets seen by the astronomers hailing from the Universities of Bern, Geneva and Zurich, indicates that there is a good chance they are composed of the same materials at similar ratios.

These are the same materials that we believe form most terrestrial planets, iron, oxygen, magnesium, and silicon. But there is a significant difference between our terrestrial world and the Trappist-1 exoplanets.

Comparison of TRAPPIST-1 to the Solar System: A planet's density is determined by its composition, but also by its size: Gravity compresses the material a planet is made of, increasing the planet's density. Uncompressed density adjusts for the effect of gravity, and can reveal how the composition of various planets compare. (NASA/JPL-Caltech 4)
Comparison of TRAPPIST-1 to the Solar System: A planet’s density is determined by its composition, but also by its size: Gravity compresses the material a planet is made of, increasing the planet’s density. Uncompressed density adjusts for the effect of gravity, and can reveal how the composition of various planets compare. (NASA/JPL-Caltech )

The planets in the Trappist-1 system appear to be about 8% less dense than the Earth. This suggests that the materials that comprise them exist in different ratios than they do throughout our home planet.

This difference in density could be the result of several different factors.

One of the possibilities being investigated by the team is that the surfaces of the Trappist-1 exoplanets could be covered with water, reducing their overall density. Combining the planetary interior models with the planetary atmosphere models, the team was able to evaluate the water content of the seven TRAPPIST-1 planets with what Martin Turbet, an astrophysicist at the University of Geneva and co-author of the study describes as “a precision literally unprecedented for this category of planets.”

For the Trappist-1 system’s four outermost planets, should water account for the difference in density, the team has estimated that water would account for 5% of their overall masses. This is considerably more than the 0.1% of Earth’s total mass made up of water.

Rust Nevers Sleeps for the Trappist-1 Planets

Another possibility that could explain why the Trappist-1 exoplanets have lower densities than Earth is the fact that they could be composed of less iron than our planet is–21% rather than the 32% found in the Earth.

It’s also possible that the iron within the seven exoplanets could be bonded with oxygen forming iron oxides–commonly known as rust. This additional oxygen would reduce the planet’s densities.

Shown here are three possible interiors of the TRAPPIST-1 exoplanets. The more precisely scientists know the density of a planet, the more they can narrow down the range of possible interiors for that planet. All seven planets have very similar densities, so they likely have a similar compositions (NASA/ JPL - Caltech)
Shown here are three possible interiors of the TRAPPIST-1 exoplanets. The more precisely scientists know the density of a planet, the more they can narrow down the range of possible interiors for that planet. All seven planets have very similar densities, so they likely have a similar composition (NASA/ JPL – Caltech)

Iron oxides give Mars its rust-red colour, but they are pretty much confined to its surface. Its core is comprised of non-oxidized iron like the solar system’s other terrestrial planets. If iron-oxide accounts for the seven exoplanet’s lower densities it implies that these worlds are rusty throughout and lacking solid non-oxidized iron cores.

“The lower density might be caused by a combination of the two scenarios – less iron overall than and some oxidized iron,” explains Eric Angol, an astrophysicist at the University of Washington and lead author of the new study. “They might contain less iron than Earth and some oxidized iron like Mars.”

Angol also points out that the Trappist-1 planets are likely to have a low-water content, an idea supported by previous research. “Our internal and atmospheric structure models show that the three inner planets of the TRAPPIST-1 system are likely to be waterless and that the four outer planets have no more than a few per cent water, possibly in liquid form, on their surfaces,” says Turbet.

This seems to favour the theory that the lower density of the Trappist-1 planets is a result of one or both of the iron scenarios suggested by the researchers.

There’s Still a Lot to Learn from Trappist-1


Since its discovery in 2o16, the Trappist system has been the subject of a wealth of observations made by both space and ground-based telescopes alike. Before it was decommissioned at the start of January 2020 the team used the Spitzer Space Telescope to collect their data. This telescope, operated by NASA’s Jet Propulsion Laboratory, alone has clocked in more than 1,000 hours of targeted observations of the exoplanets.

This new study demonstrated the importance of studying systems such as Trappist-1 for extended periods of time.

Caroline Dorn, an astrophysicist at the University of Zurich also highlights the fact that studying systems like this could answer questions about the habitability of exoplanets and the possibility of life elsewhere in the Universe.

“The TRAPPIST-1 system is fascinating because around this one star we can learn about the diversity of rocky planets within a single system,” concludes Dorn. “And we can actually learn more about an individual planet by studying its neighbours as well, so this system is perfect for that.”

“The night sky is full of planets, and it’s only been within the last 30 years that we’ve been able to start unravelling their mysteries, also for determining the habitability of these planets.”

Original Research

Agol. E., Dorn. C., Grimm. S. L., et al, ‘Refining the transit timing and photometric analysis of TRAPPIST-1: Masses, radii, densities, dynamics, and ephemerides,’ Planetary Science Journal, [https://arxiv.org/abs/2010.01074]

Space and Physics Developments to Look Forward to in 2021

Unfortunately, science journalists don’t generally carry crystal balls as part of their arsenal, and if 2020 taught us anything, it’s not always safe to predict what the forthcoming year will bring. With that said, there are some space and physics developments that we can be fairly certain that will come to pass in 2021.

These are ZME Science’s tips for the top space science and physics events scheduled to occur in 2021.

Back to the Beginning with the James Webb Launch

It’s almost impossible to talk about the future of astronomy without mentioning NASA’s forthcoming James Webb Space Telescope (JWST). To call the launch of Webb ‘much-anticipated’ is a vast understanding.

The fully assembled James Webb Space Telescope with its sunshield and unitized pallet structures that will fold up around the telescope for launch (NASA)

The reason astronomers are getting so excited about the JWST is its ability to see further into the Universe, and thus further back in its history than any telescope ever yet devised. This will allow astronomers to observe the violent and tumultuous conditions in the infant Universe. Thus, it stands poised to vastly improve our knowledge of the cosmos and its evolution.

Part of the reason for JWST’s impressive observational power lies in its incredible sensitivity to infrared light–with longer wavelengths than light visible with the human eye.

The ability to observe the early Universe could help settle confusion about what point in its history galaxies began to form. Whilst the current consensus is that galaxies began to form in later epochs, a wealth of recent research has suggested that galaxies could have formed much earlier than previously believed.

“Galaxies, we think, begin building up in the first billion years after the big bang, and sort of reach adolescence at 1 to 2 billion years. We’re trying to investigate those early periods,” explains Daniel Eisenstein, a professor of astronomy at Harvard University and part of the JWST Advanced Deep Extragalactic Survey (JADES). “We must do this with an infrared-optimized telescope because the expansion of the universe causes light to increase in wavelength as it traverses the vast distance to reach us.”

An artist’s impression of the JWST in place after its 2021 launch (ESA)

The reason infrared is so important to observe the early Universe is that even though the stars are emitting light primarily in optical and ultraviolet wavelengths, travelling these incredible distances means light is shifted into the infrared.

“Only Webb can get to the depth and sensitivity that’s needed to study these early galaxies.”

Daniel Eisenstein, Havard University

After years of setbacks and delays and an estimated cost of $8.8 billion the JWST is set to launch from French Guiana, South America, on 31st October 2021.

JET Will Have Star Power

The race is on to achieve fusion power as a practical energy source here on Earth. Nuclear fusion is already the process that powers the stars, but scientists are looking to make it an energy source much closer to home.

Internal view of the JET tokamak superimposed with an image of a plasma ( EFDA-JET)

When it comes to bringing star power down to Earth the Joint European Torus (JET)–the world’s largest tokamak–leads the way, housing plasmas hotter than are found anywhere else in the solar system, barring the Sun.

A tokamak is a device that uses a powerful magnetic field to trap plasma, confining it in a doughnut-like shape. Containing and controlling these plasmas is the key to generating energy through the fusion process. Within the plasma, particles collide with enough energy to fuse together forming new elements and releasing energy.

The process is cleaner and more efficient than fission power, which rips the atoms of elements apart, liberating energy whilst leaving behind radioactive waste.

JET itself isn’t a power station, rather it was designed to conduct experiments with plasma containment and study fusion in conditions that approach that which will be found in working fusion power plants. So, whilst the International Thermonuclear Experimental Reactor (ITER)–set to be the world’s largest tokamak–is still under construction and won’t be operational until at least 2025, this year is set to be an important year for the experiment that inspired it.

Following upgrades conducted during 2020, JET is scheduled to begin experiments with a potent mix of the hydrogen isotopes deuterium and tritium (D-T). This fuel hasn’t been used since 1997 due to the difficulties presented by the handling of tritium– a rare and radioactive isotope of hydrogen with a nucleus of one proton and two neutrons.

The JET team will be looking to attain an output similar to the 16 megawatts of power that was achieved in ’97, but for a more sustained period and with less energy input. The initial test at the end of the 20th century consumed more power than it produced.

Back to the Moon in 2021

2021 will mark the 52nd anniversary of NASA’s historic moon landing and will see the launch of several missions back to Earth’s natural satellite as well as continuing efforts to send humans following in the footsteps of Armstrong and the crew of Apollo 11.

Illustration of Orion performing a trans-lunar injection burn (NASA)

As part of NASA’s deep space exploration system, Artemis I is the first in a series of increasingly complex missions designed to enable human exploration of the Moon and beyond.

“This is a mission that truly will do what hasn’t been done and learn what isn’t known. It will blaze a trail that people will follow on the next Orion flight, pushing the edges of the envelope to prepare for that mission.” 

Mike Sarafin, the Artemis I mission manager.

Artemis I will begin its journey aboard the Orion spacecraft, which at the time of its launch in November will be the most powerful spacecraft ever launched by humanity producing a staggering 8.8 million pounds of thrust during liftoff. After leaving Earth’s orbit with the aid of solar arrays and the Interim Cryogenic Propulsion Stage (ICPS) Orion will head out to the moon deploying a number of small satellites, known as CubeSats.

After a three week journey to and from the moon and six weeks in orbit around the satellite, Orion will return home in 2022, thus completing a total journey of approximately 1.3 million miles.

The Chandrayaan 2 launch. The ISRO will be hoping for better luck with Chandrayaan 3 in 2021 (ISRO)

NASA isn’t the only space agency with its sights set on the moon in 2021. The Indian Space Research Organisation (ISRO) will launch the Chandrayaan-3 lunar lander at some point in 2021. It will mark the third lunar exploration mission by ISRO following the Chandrayaan-2’s failure to make a soft landing on the lunar surface due to a communications snafu.

Chandrayaan-3 will be a repeat of this mission including a lander and rover module, but lacking an orbiter. Instead, it will rely on its predecessor’s orbiter which is still in good working despite its parent module’s unfortunate crash lander. Should Chandrayaan-3 succeed it will make India’s ISRO only the fourth space agency in history to pull off a soft-landing on the lunar surface.

(Robert Lea)

Back with a Blast: The LHC Fires Up Again

The world’s largest, most powerful particle accelerator, the Large Hadron Collider (LHC) ceased operations in 2018 and this year, after high-luminosity upgrades, it will begin to collide particles again.

During its first run of collisions from 2008 to 2013 physicists successfully uncovered the Higgs Boson, thus completing the standard model of particle physics. With the number of collisions increased significantly, in turn, increasing the chance of spotting new phenomenon, researchers will be looking for clues of physics beyond the standard model.

All quiet at the LHC in 2019, but the world’s largest particle accelerator will fire up again in 2021 (Robert Lea)

The function of the LHC is to accelerate particles and guide them with powerful magnets placed throughout a circular chamber that runs for 17 miles beneath the French-Swiss border. When these particles collide they produce showers of ‘daughter’ particles, some that can only exist at high energy levels.

These daughter particles decay extremely quickly–within fractions of a second– and thus spotting them presents a massive challenge for researchers.

Luminosity when used in terms of particle accelerators refers to the number of particles that the machine can accelerate and thus collide. More collisions mean more daughter particles created, and a better chance of spotting exotic and rare never before seen particles and phenomena. Thus, high luminosity means more particles and more collisions.

To put these upgrades in context, during 2017 the LHC produced around 3 million Higgs Boson particles. When the High-Luminosity LHC (HL-LHC) begins operations, researchers at cern estimate it will be producing around 15 million Higgs Bosons per year.

After being shut down for upgrades in 2018, the LHC prepares to fire up again in 2021 (CERN)

Unfortunately, despite firing up for a third run after these high luminosity upgrades, there is still work to be done before the LHC becomes the HL-LHC.

The shutdown that is drawing to completion–referred to by the CERN team as  Long Shutdown 2 (LS2)–was just part of the long operations that are required to boost the LHC’s luminosity. The project began in 2011 and isn’t expected to reach fruition until at least 2027.

That doesn’t mean that the third run of humankind’s most audacious science experiment won’t collect data that reveals stunning facts about the physics that governs that cosmos. And that collection process will begin in 2021.

Astronomers witness the ‘death’ of a galaxy

The process that causes the end of star formation in galaxies, their transition to an inactive phase and thus their figurative ‘death’ has been a puzzle for astronomers and astrophysicist for some time. Many researchers believe that ‘galactic death’ begins with the ejection of a massive quantity of gas, but thus far, researchers have failed to capture evidence of the escape of this star-forming fuel in such volumes. Thus the confirmation of how this transition to galactic quintessence occurs has also proved elusive.

Now an international team of astronomers have used the  Atacama Large Millimeter/submillimeter Array (ALMA) located in the desert region of Chile to spot a distant galaxy in which such a massive ejection of gas is progressing.

“Using ALMA we have discovered a distant galaxy, ID2299, which is ejecting about half of its cold gas reservoir out of the galaxy,” Annagrazia Puglisi, Centre for Extragalactic Astronomy, Durham University, lead researcher on the study, tells ZME Science. “This is the first time we have observed a typical massive star-forming galaxy in the distant Universe about to ‘die’ because of a massive cold gas ejection.”

This artist’s impression of ID2299 shows the galaxy, the product of a galactic collision, and some of its gas being ejected by a “tidal tail” as a result of the merger. New observations made with ALMA, in which ESO is a partner, have captured the earliest stages of this ejection, before the gas reached the very large scales depicted in this artist’s impression. (ESO/M. Kornmesser)
This artist’s impression of ID2299 shows the galaxy, the product of a galactic collision, and some of its gas being ejected by a “tidal tail” as a result of the merger. New observations made with ALMA, in which ESO is a partner, have captured the earliest stages of this ejection before the gas reached the very large scales depicted in this artist’s impression. (ESO/M. Kornmesser)

ID2299 is so distant that the light it emits takes 9 billion years to reach Earth, which means the team were able to observe it at a time when the universe was just 4.5 billion years old.

The rate of gas ejection that ID2299–a galaxy with a similar mass to the Milky way– is experiencing is equivalent to 10,000 Suns per year, removing an extraordinary 48% of its total cold gas content. In addition to this, the galaxy is still forming stars at a rapid rate, hundreds of times faster than the star formation rate of our own galaxy.

Puglisi explains that the gas ejection, together with a large amount of star formation in the nuclear regions of the galaxy, will eventually deprive the galaxy of the fuel need to make new stars.

“This would stop star formation in the object, effectively halting the galaxy’s development.”

Annagrazia Puglisi, Centre for Extragalactic Astronomy, Durham University

The team’s research, published in the latest edition of the journal Nature Astronomy, is significant because it represents three ‘firsts’ for astronomy. “This is the first time we observe a typical massive star-forming galaxy in the distant Universe about to ‘die’ because of a massive cold gas ejection,” explains Puglisi. “Also, for the first time, we were able to tell that massive gas ejection might be frequent enough to cause the cessation of star formation in a large number of massive distant galaxies. Finally, we were able to study the physical properties of the ejected gas in a distant galaxy.”

The researcher goes on to explain that these factors are important in the understanding of the triggering mechanism of the ejection– the galaxy’s distinct tidal tail.

Galactic Collisions and Tidal Tails

The research team that discovered ID2299 believe that it was created during a collision between two galaxies and their eventual merger. Ironically this process seems to have triggered the rapid gas loss that will eventually cause it to become inactive.

Another stunning example of a tidal tail is the ‘Tadpole’s Tail’ emerging from the galaxy Arp 188. This tail stretches a stunning 280 thousand light years and was caused by a gravitational interaction with another galaxy. (Hubble Legacy Archive/ NASA/ ESA)

“ID2299 is a galaxy with a large mass in stars and is forming new stars at a rate 300 times faster than our Galaxy– a result of the collision between two galaxies,” co-author Chiara Circosta, Department of Physics & Astronomy, University College London, tells ZME.

The main clue that points towards ID2299’s creation by collision is the fact its ejected gas has taken the form of a tidal tail. These elongated streams of stars and gas that reach into interstellar space are often too faint to see and are theorised to be the result of galactic mergers.

“Collisions between galaxies are very powerful and spectacular phenomena. During the interaction, tidal forces develop and can trigger ejection of gas through tidal tails,” says Circosta. “Our study suggests that these ejections could be frequent enough to stop the formation of new stars in a large number of massive galaxies in the distant Universe.

“Our research shows that these interactions can have an important role in the life-cycles of galaxies.

Chiara Circosta, Department of Physics & Astronomy, University College London


What makes the team’s findings even more impressive is the fact that it’s a discovery that occurred predominantly through good fortune.

Serendipity and a Series of Firsts

Because tidal tails of gas such as the one that the team observed being ejected from ID2299 are extremely faint and thus, difficult for astronomers to observe. In fact, the team weren’t looking for a galaxy like ID2299 at all.

“The discovery of this object was serendipitous. I was inspecting the spectra of 100 star-forming galaxies from the ALMA telescope,” says Puglisi, who goes on to explain that the spectrum of galaxy ID2299 immediately caught her attention as it displayed an excess of emission near the very prominent emission line from the galaxy. “I was very surprised when I measured the flux of this excess emission because it indicated that the galaxy was expelling a large amount of gas.

 “I was thrilled to discover such an exceptional galaxy! I was eager to learn more about this weird object because I was convinced that there was some important lesson to be learned about how distant galaxies evolve.

Annagrazia Puglisi, Centre for Extragalactic Astronomy, Durham University

The discovery of ID2299 sparked a discussion within the team about the mechanism that is causing the gas ejection of gas at such a rapid rate. They concluded that alternative mechanisms simply couldn’t account for ejection in such large amounts.

“We discussed a lot to understand what could have been the possible cause of this phenomenon. Broad components are fairly common in the spectra of distant galaxies and are typically associated with galactic winds,” says Puglisi. “Nor the active black hole nor the strong star formation hosted in ID2299 were powerful enough to produce this ejection.

“The numbers didn’t just add up.”

The ALMA antennas at the Llano Chajnantor–above them, the bright Milky Way is visible–played a vital role in the discovery of ID2299 and will now assist in the further investigation of gas movements in the galaxy (ESO/Y. Beletsky)

The next steps for the team are to use ALMA to make high-resolution observations of ID2299 and the motion of gas within it in order to better understand the gas ejection occurring there. Looking beyond this galaxy, Puglisi says she will also look for similar occurrences in other galaxies.

“I personally find quite fascinating the study of galaxy interactions and mergers. These phenomena are visually spectacular,” the researcher adds. “I find quite poetic that galaxies can get close to each other and influence their life and evolution so dramatically.”

The research the team presents could either overturn current theories that suggest star-forming material is actually ejected by the activity of supermassive black holes at the centre of galaxies or could provide another mechanism by which this can occur. Either way, the discovery represents a significant step forward in our understanding of how galaxies develop.

“I see galaxy evolution as a complex puzzle that researchers are trying to complete through their studies,” Circosta concludes. “A crucial part of the puzzle is about the mechanisms that halt the formation of new stars and ‘kill’ galaxies.

“Witnessing such a massive disruption event allowed us to shed new light on one of the possible culprits responsible for the death of distant galaxies. This adds an important piece to the puzzle of galaxy evolution!”

Chiara Circosta, Department of Physics & Astronomy, University College London

Original research:

Puglisi. A., Daddi. E., Brusa. M., et al, ‘A titanic interstellar medium ejection from a massive starburst galaxy at z=1.4,’ Nature Astronomy, [2021], [DOI: 10.1038/s41550-020-01268-x].

Baby universes branching off of our universe shortly after the Big Bang appear to us as black holes. (Kavli IPMU)

Primordial black holes could hide a multiverse of possibilities

Before the stars and galaxies even began to form in the early Universe, some researchers believe that the cosmos could have been occupied by a multitude of tiny primordial black holes. These purely hypothetical black holes would have formed in a radically different way than larger and more familiar black holes which physicists, cosmologists, and astronomers have confirmed to exist. 

Whereas larger black holes form as a result of the death of massive stars, primordial black holes would have been born immediately after the ‘Big Bang’ when areas of high density underwent gravitational collapse. Despite having a long history in theoretical physics, primordial black holes had moved out of favour, that is until recently.

Baby universes branching off of our universe shortly after the Big Bang appear to us as black holes. (Kavli IPMU)
Baby universes branching off of our universe shortly after the Big Bang appear to us as black holes. (Kavli IPMU)

Now researchers from the Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) — including Kavli IPMU members Alexander Kusenko, Misao Sasaki, Sunao Sugiyama, Masahiro Takada and Volodymyr Takhistov —  are studying the possibility of such objects existing both in the early Universe and in our current epoch.

The team believes the discovery of primordial black holes could point to a potential multiverse, with other ‘baby universes’ born alongside our own. Meaning that behind the event horizon — the point at which not even light can escape — of these primordial black holes could lurk an entire universe, hidden from view.

The scientists’ findings are documented in a paper published in the journal Physical Review Letters.

Beyond the discovery of these early black holes themselves, such an investigation could answerquestions surrounding many lingering and mysterious aspects of physics. 

Primordial Black holes and Lingering Mysteries

The team believes that the existence of primordial black holes could account for a small amount of the gravitational waves detected at the LIGO/VIRGO interferometer. Until recently, this had been ruled out as primordial black holes existing binary pairs should result in more gravitational-wave signals than we currently detect. 

Recent research has begun to illustrate how primordial black holes could exist and still produce gravitational wave signals that conform to the number detected at LIGO. 

Such objects could even explain how some heavy elements are synthesised. Should primordial black holes exist, they could either collide with neutron stars — obliterating them — or infest the centres of such stellar remnants and ‘eat them’ from the inside out. Either of these processes would lead to the release of neutron-rich material would be released. 

the team searched the Andromeda galaxy with the HSC for clues indicating the prescence of primordial black holes (Kavli IPMU/HSC Collaboration)

The synthesis of heavy elements has puzzled astrophysicists for some time, as the processes behind it rely on the presence of large numbers of neutrons, meaning primordial black holes could play a key role in providing such neutron-rich conditions. 

Perhaps more exciting than this even; the team’s research could reveal if primordial black holes comprise the majority of dark matter — the mysterious substance which makes up between 80–90% of the Universe’s total matter content.

The idea that primordial black holes could account for dark matter — or at least some of it — isn’t a new idea. But, like the discussion of these objects themselves, theories connecting them to dark matter have also fallen out of favour over recent years. 

In order to discover primordial black holes, the Kalvi team used the Hyper Suprime-Cam (HSC) of the 8.2m Subaru Telescope, a gigantic digital camera at the summit of Mount Mauna Kea, Hawaii to study the early Universe for clues.

 Searching the Early Universe for Primordial Black Holes

Because the early Universe was so dense, it would take only a small density fluctuation of around 50% to create a black hole. This means, that whilst the gravitational perturbations that created galaxies were much smaller than this, there are a variety of events in the early cosmos that could have triggered the start of such a genesis event.

One such process would be the creation of a small ‘daughter universe’ branching off from our own universe during its initial period of rapid inflation. Should this baby universe collapse a vast amount of energy would be released within its small volume, thus giving rise to a tiny black hole. 

This idea of branching Universes gets even stranger, however, should one of these baby-universes reach and exceed some critical size. General relativity suggests that if this was to happen the universe in question would exist in a state that appears different from the inside than it does from the outside. 

Hyper Suprime-Cam (HSC) is a gigantic digital camera on the Subaru Telescope ideal fr spotting primordial black holes (HSC project / NAOJ)

An observer from with the baby universe would see it as an expanding universe, whilst an observer outside the event horizon would see the baby universe as a black hole. This means that in both cases, the event horizon of the primordial black hole hides its internal structure — and an entire universe. 

The team’s paper points to a scenario in which primordial black holes are created by this nucleation of what they term ‘false vacuum bubbles.’ 

The fact that primordial black holes have thus far escaped detection indicates it is going to take an extremely powerful instrument to see the Universe in such a way that these multiverse camouflaging objects can be spotted.

Fortunately the HSC fits the bill.

The Hyper Suprime-Cam sees the Big Picture

As the paper’s authors describe, thanks to its unique capability to picture the entire Andromeda galaxy every few minutes, the HSC could be the ideal instrument to capture primordial black holes. This imaging can be achieved with the aid of gravitational lensing, the curvature of light by an object of great mass.

The team used gravitational lensing, the curvature of light by objects with tremendous mass, to help identify primordial black holes. (Kavli IPMU/HSC Collaboration)
The team used gravitational lensing, the curvature of light by objects with tremendous mass, to help identify primordial black holes. (Kavli IPMU/HSC Collaboration)

As a primordial black hole passes the line of sight to a bright object such as a star, the curvature it causes in spacetime results in a momentary brightening of the object or an apparent shift in position. 

The greater the mass, the more extreme the curvature and thus the stronger the effect meaning that the astronomers can measure the mass of the lensing object. This effect only lasts an extremely brief time, however.

Because the HSC can see the entire galaxy, it can simultaneously observe up to one hundred million stars — giving astronomers a good chance of catching a transiting primordial black hole. 

The team have already identified a prime candidate for a ‘multiverse’ hiding primordial black hole in the first run of HSC observations. The object had a mass around that of the Moon and has inspired the team to conduct further observations, thus widening their search and possibly finding a solution to some of physics’ most pressing mysteries. 

Original Research

Kusenko. A., Sasaki. M., Sugiyama. S., et al, [2021], ‘Exploring Primordial Black Holes from the Multiverse with Optical Telescopes,’ Physical Review Letters, [https://doi.org/10.1103/PhysRevLett.125.181304]

2020: A Year in Space

It’s difficult to mention the year 2020 without referencing COVID-19, but as more human beings than ever before were wishing they could take a break from the surface of the planet, space research continued to push our knowledge of the stars. Whilst much of the scientific community was consumed with combating a pandemic, physicists, astronomers, cosmologists, and other researchers were further pushing our understanding of space and the objects which dwell there.

These are some of my personal favourite space-related breakthroughs and research that have come about this year. The list is by no means exhaustive. 

Black Holes go silent

In terms of black hole science, 2019 was always going to be a difficult year to top being the year that brought us the first direct image of a supermassive black hole (SMBH). That doesn’t mean that 2020 has been a slow year for black hole developments, however.

One of the most striking and memorable examples of black hole research announced this year was the discovery of a ‘silent’ black hole in our cosmic ‘back yard.’ An international team led by researchers from European Southern Observatory (ESO) including found the black hole in the system HR 6819, located within the Milky Way and just 1,000 light-years from the Earth.

A silent and thus invisible black hole discovered lurking in our ‘solar backyard’ could be an indicator of a much larger population. (ESO/L. Calçada) Background: This wide-field view shows the region of the sky, in the constellation of Telescopium, where HR 6819 can be found. (ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin)

The observation marks the closest to Earth a black hole has ever been discovered and Dietrich Baade, Emeritus Astronomer at ESO in Garching believes that it is just ‘the tip of the Iceberg’. 

“It’s remarkable because not only is it the first of its kind found, but it’s also so nearby,” said Baade. “Discovering a first only an astronomical stone’s throw away is the biggest surprise one can probably imagine.”

The black hole was described as ‘silent’ by the team because it is not current accreting material — the destructive process that creates powerful x-ray emissions and makes these light-trapping objects observable. 

Close-up screen capture image of the LB-1 which, like HR 6819, could also host a silent black hole (Hubble/Public Domain)

“If there is one, there ‘must’ be more,” Baade remarked in May. “If the Earth is not in a privileged position in the Universe — and all available evidence suggests without a doubt it is not — this means that there must be many more silent black holes.”

Baade also remarked that as current cosmological models suggest that the number of stellar-mass black holes is between 100,000,000 to 1,000,000,000 and we have observed nowhere near this many objects, more quiet black holes are “badly needed” to confirm current models. “HR 6819 is the tip of an iceberg, we do not yet know how big the iceberg is.”

Silent black holes weren’t the only examples of this hind of science making noise in 2020, however. Long-missing Intermediate Mass Black Holes were discovered. And just like a proverbial bus, you wait decades for one and then two turn up at once.

Intermediate mass black holes found and found again

Missing black holes were the subject of another piece of exciting space science in September 2020, when researchers from the VIRGO/LIGO collaboration discovered the tell-tale signal of an intermediate-mass black hole (IMBH) in gravitational-wave signals. To add to the excitement, the signals originated from the largest black hole merger ever observed.

An artistic interpretation of the binary black hole merger responsible for GW190521. The space-time, figured by a fabric on which a view of the cosmos is printed, is distorted by the GW190521 signal. The turquoise and orange mini-grids represent the dragging effects due to the individually rotating black holes. The estimated spin axes, or self-rotations, of the black holes, are indicated with the corresponding coloured arrows. The background suggests a star cluster, one of the possible environments where GW190521 could have occurred. Credits: Raúl Rubio / Virgo Valencia Group / The Virgo Collaboration.)

The merger — identified as gravitational wave event GW190521 —was detected in gravitational waves and is the first example of a ‘hierarchical merger’ occurring between two black holes of different sizes, one of which was born from a previous merger.

“This doesn’t look much like a chirp, which is what we typically detect,” Virgo member Nelson Christensen, a researcher at the French National Centre for Scientific Research (CNRS) said when announcing the team’s observation. “This is more like something that goes ‘bang,’ and it’s the most massive signal LIGO and Virgo have seen.”

The black hole birthed in the detected merger appears to have a mass of between 100–1000 times that of the Sun — most likely 142 solar masses — putting it in the mass range of an IMBH — a ‘missing link’ between stellar-mass black holes and much larger SMBHs. 

Earlier in 2020, another team had used the Hubble Space Telescope X-ray data collected in 2018 to identify what they believed to be an IMBH with a mass 50,000 times that of the Sun named 3XMM J215022.4−055108 (or J2150−0551 for short). 

This Hubble Space Telescope image identified the location of an intermediate-mass black hole (IMBH), weighing over 50 000 times the mass of our Sun (NASA, ESA, and D. Lin (University of New Hampshire))

Whether GW190521 or J2150−0551 will go down in history as the first discovered IMBH is currently a little muddy, but what is less questionable is that 2020 will go down as the year in which these ‘missing link’ black holes were first discovered, bringing with them exciting implications for the future investigation of black holes of all sizes. 

“Studying the origin and evolution of the intermediate-mass black holes will finally give an answer as to how the supermassive black holes that we find in the centres of massive galaxies came to exist,” said Natalie Webb of the Université de Toulouse in France, part of the team that found J2150−0551. And IMBHs weren’t the only missing element of the Universe that turned up in 2020.

Discovering the Universe’s missing mass

In May astronomers, including Professor J. Xavier Prochaska of UC Santa Cruz, announced that they had found the missing half of missing baryonic matter demanded by cosmological models. 

“The matter in this study is ‘ordinary’ matter — the material that makes up our bodies, the Earth, and the entirety of the periodic table. We refer to this matter as ‘baryonic’–matter made up of baryons like electron and protons,” Prochaska said when he spoke exclusively to ZME Science earlier this year. “Of particular interest to astronomers is to ascertain the fraction of the material that is tightly bound to galaxies versus the fraction that is out in the open Universe — what we refer to as the intergalactic medium or cosmic web.”

The matter the team discovered isn’t ‘dark matter’ — which accounts for roughly 85–90% of the Universe’s matter content — but rather ‘ordinary’ matter that has been predicted to exist by our models of universal evolution but has remained hidden.

The team made the discovery using mysterious Fast Radio Bursts (FRBs) and the measurement of the redshift of the galaxy from which they originate as a detection method. FRBs can be used as a probe for baryonic matter because as they travel across the Universe, every atom they encounter slows them down by a tiny amount.

This means that they carry with them a trace of these encounters along with them in the spectral splitting as seen above. This allowed the team to infer the presence of clouds of ionised gas that are invisible to ‘ordinary’ astronomy because of how diffuse they are. 

Asteroid Samples Returned by Hayabusa2

Japan’s Hayabusa2 probe and its continued investigation of the asteroid Ryugu has been the gift that has just kept giving in 2020. Just this month the probe returned to Earth samples collected from an asteroid — which has an orbit that brings it between Earth and Mars — for the first time.

Though probes have landed on asteroids and collected samples before, these samples have been examined in situ. Thus this is the first time researchers have been able to get ‘up close and personal’ with matter from an asteroid.

Artist’s impression of the Hayabusa2 probe achieving touchdown on Ryugu. Image credit: JAXA

Hayabusa2 arrived at Ryugu in late June 2018, making its touch-down on the surface of the asteroid in February of the following year after months careful manoeuvring conducted by the Japan Aerospace Exploration Agency (JAXA) and the selection of an optimal region from which to collect samples. 

Ahead of the return of samples on December 5th, the probe sent back some stunning images of the asteroid’s surface. These images were more than purely aesthetic, however. Examination of dust grains on the surface of Ryugu gave the team, including Tomokatsu Morota, Nagoya University, Japan, indications of a period of rapid heating by the Sun. 

The surface of near-Earth carbonaceous asteroid 162173 Ryugu, as observed by the Hayabusa2 spacecraft just before its landing. This image was produced from images obtained by ONC-W1 at the bottom and ONC-W2 on the side of the spacecraft. The spacecraft’s solar ray paddle casts a shadow on Ryugu’s surface. Image credit: JAXA/U. Tokyo/Kochi U./Rikkyo U./Nagoya U./Chiba Inst. Tech./Meiji U./U. Aizu/AIST

“Our results suggest that Ryugu underwent an orbital excursion near the
Sun,” said Morota in May. “This constrains the orbital transition processes of asteroids from the main belt to near-Earth orbit.”

Impressive though this achievement is, its the collection of samples from the asteroid and their subsequent safe return to earth that is the ‘main course’ of the Hayabusa2 mission. “The most important objective of the touchdown is sample collection from Ryugu’s surface,” Morota explained. 

Animation created from CAM-H and ONC-W1 data obtained during the 1st touchdown operation (Feb. 21, 2019). Image credit: JAXA/U. Tokyo/Kochi U./Rikkyo U./Nagoya U./Chiba Inst. Tech./Meiji U./U. Aizu/AIST

It is hoped that access to these samples will help answer lingering questions about asteroid composition as well as assisting researchers to confirm Ryugu’s suspected age of 100 million years old — which actually makes it quite young in terms of other asteroids. 

Asteroids like Ryugu can act as a ‘snapshot’ of the system’s in which they form at the time of that formation. This is because whereas planets undergo a lot of interaction with other bodies, asteroids remain pretty much untouched. 

Whilst researchers will no doubt be elated by the return of the Ryugu samples and the continuing success of the Hayabusa2 mission, 2020 wasn’t all good news for fans of asteroid research. 

Goodbye to Arecibo

The iconic radio telescope at the Arecibo Observatory in Puerto Rico collapsed at the beginning of December, ahead of its planned demolition. The telescope which will be familiar to moviegoers as the setting of the climactic battle in Pierce Brosnan’s first outing as James Bond, 1995’s Goldeneye, had been in operation up until November, playing a role in the detection of near-Earth asteroids and monitoring if they present a threat to the planet.

An image of the radio telescope before its December 1st collapse (NSF)

The collapse of the radio telescope’s 900-tonne platform which was suspended above the telescope’s 305-metre-wide dish, on December 1st, followed the snapping of one of its main cables in November.

The US National Science Foundation (NSF), which operates the observatory had announced that same month that the telescope would be permanently closed citing ‘safety concerns’ after warnings from engineers that it could collapse at any point.

Following the collapse, the NSF release heart-wrenching footage of the radio telescope collapsing recorded by drones. The footage shows cables snapping at the top of one of the three towers from which the instrument platform was suspended. The platform then plummets downward impacting the side of the dish. 

Video shows the radio telescope’s instrument platform fall and collision into the side of the dish (NSF)

The observatory had played a role in several major space-science breakthroughs since its construction in 1963. Most notably, observations made by the instrument formed the basis of Russell A. Hulse and Joseph H. Talyor’s discovery of a new type of pulsar in 1974. The breakthrough would earn the duo the 1993 Nobel Prize in Physics. 

Some good could ultimately come out of the collapse of Arecibo. Questions had been asked about the maintenance of the radio telescope for some time and the fact that the cable which snapped in November dated back to the instrument’s construction 57 years ago has not escaped notice and comment.

As a result, various space agencies are being encouraged to make efforts to better maintain large-scale equipment and facilities so that losses like this can be avoided in the future.

This aerial view shows the damage at the Arecibo Observatory after one of the main cables holding the receiver broke in Arecibo, Puerto Rico, on December 1, 2020. – The radio telescope in Puerto Rico, which once starred in a James Bond film, collapsed Tuesday when its 900-ton receiver platform fell 450 feet (140 meters) and smashed onto the radio dish below. (Photo by Ricardo ARDUENGO / AFP) (Photo by RICARDO ARDUENGO/AFP via Getty Images)

For most of us, 2020 is going to be a year that we would rather forget. Whilst very few of us come honestly comment that we have had anything approaching a ‘good year’ space science has plowed ahead, albeit mildly hindered by the global pandemic.

Our knowledge and understanding of space science are better off at the end of 2020 than it was twelve months earlier, and that is at least something positive that has emerged from this painful year.

Astronomers find two failed stars wandering the universe together

A team of researchers from the University of Bern has discovered a very different binary system 450 light-years from Earth. The system — CFHTWIR-Oph 98 or Oph 98 for short — has twin occupants that appeared at first sight to be exoplanets existing in a star-less system. A deeper examination has revealed that they are brown dwarfs — Oph 98 A and Oph 98 B respectively — astronomical objects that are similar to stars but smaller and cooler.

This artist’s illustration represents a couple of planetary-mass brown dwarfs Ophiuchus 98. As they are very young, they are still evolving in the molecular clouds that saw their birth. (University of Bern, Illustration: Thibaut Roger)

These brown dwarfs wander the galaxy together, orbiting each other at an incredibly large distance equivalent to 200 times the distance between Earth and the Sun.

The discovery of the curious Oph 98 system by the research team led by Clémence Fontanive from the Center for Space and Habitability (CSH) and National Centre of Competence in Research PlanetS (NCCR PlanetS) is documented in a paper published in The Astrophysical Journal Letters.

A Star that Failed

The Oph 98 is a relativity new-born system in astrophysical terms, forming just 3 million years ago in the Ophiuchus stellar nursery (hence the ‘Oph’ element of its name). Its relative youth has some interesting consequences for the bodies that comprise it and led the team to properly identify its constituent bodies. 

The system has not existed for long enough for it to start forming planets. This means that Oph 98 A and B must have both formed via the same mechanisms that give rise to stars. This conclusion is also supported by the fact that Oph 98 B is roughly the right size to be a planet, but Oph A is too small to have the reservoir of material needed to form a planet so large. That means they must be brown dwarfs.

“This tells us that Oph 98 B, like its host, must have formed through the same mechanisms that produce stars and shows that the processes that create binary stars operate on scaled-down versions all the way down to these planetary masses,” says Fontanive.

In terms of mass brown dwarfs exist between planets and stars (NASA/ Caltech/ R. Hurt (IPAC).)

The fact that brown dwarfs form in ways that are similar to stars and share similar masses, but do not ignite with the nuclear processes that power stars, has often led to them being nicknamed ‘failed stars.’ It is extremely rare for star-forming processes to create worlds that go on to exist in a system such as this. 

The objects are rare examples of astronomical bodies similar to giant exoplanets that orbit each other without a parent star. Both are young brown dwarfs, with Oph 98 A being the larger of the two with a mass 15 times that of Jupiter. Its smaller companion — Oph 98 B — has a mass equivalent to 8 times that of the gas giant, which is the largest body other than the Sun in our solar system.

This isn’t the only thing that makes Oph 98 unique, however. 

Brown Dwarfs with a Weak Bond

Another thing that makes the Oph 98 system so remarkable is the fact that, like all binary systems, the bodies are gravitationally bound. These bonds are greater with objects of greater mass but follow an inverse square law — meaning the bond’s strength falls off quickly as separation distances increase. Because these objects have relatively small mass coupled with an extremely large separation, the gravitational bond between them is one of the weakest in terms of energy that astronomers have ever observed. 

Observing this system at all is no mean feat as brown dwarfs — especially low-mass ones — emit very little electromagnetic radiation and are thus, not easy to spot.

“Low-mass brown dwarfs are very cold and emit very little light, only through infrared thermal radiation,” explains Fontanive. “This heat glow is extremely faint and red, and brown dwarfs are hence only visible in infrared light.” 

The Ophiuchus cluster that is home to Oph 98 sits in a cloud of dust that makes it difficult to see. In this image it is pictured in X-rays by the Chandra X-Ray Observatory (Chandra X-Ray Observatory)

This visibility challenge was further compounded by the fact that Oph 98 and the Ophiuchus galaxy cluster itself is embedded in a dense cloud of dust that scatters visible light. “Infrared observations are the only way to see through this dust,” the researcher adds.

In fact, the team’s discovery was only made possible by the impressive power of the Hubble Space Telescope and the fact that it makes its observations from above Earth.

Hubble Shines Through Again

The Hubble Space Telescope is one of the only telescopes capable of observing objects as faint as the Oph 98 A and B and resolving the image of the brown dwarfs at such tight angles.

“Detecting a system like Oph 98 also requires a camera with a very high resolution, as the angle separating Oph 98 A and B is a thousand times smaller than the size of the moon in the sky,” Fontanive continues. 

The Hubble Space telescope’s vantage point above Earth’s atmosphere allows it to spot water vapor from brown dwarfs (ESA)

Hubble’s space-based vantage point is also crucial for the observation of such objects. This is because the infrared signatures that are used to observe brown dwarfs arise from water vapors that form in their upper atmospheres. As Earth’s atmosphere is full of water also producing this signal, the fainter trace from distant brown dwarfs is almost always obscured beyond detection for telescopes at the planet’s surface. 

“Both objects looked very red and showed clear signs of water molecules. This immediately confirmed that the faint source we saw next to Oph 98 A was very likely to also be a cold brown dwarf, rather than a random star that happened to be aligned with the brown dwarf in the sky,” says Fontanive.

The team also found Oph 98 in data collected by the CFHT (pictured) 14 years ago. (CFHT)

Interestingly, the team’s findings have helped confirm the fact that the Oph 98 system has actually been spotted before. The binary was also visible in data collected by the Canada-France-Hawaii Telescope (CFHT), located atop the summit of Mauna Kea, Hawaii, 14 years ago. This older data helped the team confirm how Oph 98 A and B move together across the galaxy as a pair.

“We observed the system again this summer from another Hawaiian observatory, the United Kingdom Infra-Red Telescope. Using these data, we were able to confirm that Oph 98 A and B are moving together across the sky over time, relative to other stars located behind them, which is evidence that they are bound to each other in a binary pair”, explains Fontanive. “We are really witnessing an incredibly rare output of stellar formation processes.”

Original Research

Fontanive. C., et al, ‘A wide planetary-mass companion to a young low-mass brown dwarf in Ophiuchus,’ The Astrophysical Journal Letters, [2020], [https://arxiv.org/abs/2011.08871]

A Big Blue Marble. A History of Earth from Space

“As the Sun came up I was absolutely blown away by how incredibly beautiful our planet Earth is. Absolutely breathtaking. Like someone took the most brilliant blue paint and painted a mural right in front of my eyes. I knew right then and there that I would never, ever see anything as beautiful as planet Earth again.”

Scott Kelly, Former NASA Astronaut
The Blue Marble. Taken by the crew of Apollo 17 in 1972 at a distance of 29,000 km above the planet. (NASA/Apollo 17 crew)

There is a common experience shared by human beings who visit that edge of space when they turn back and look upon their home planet. In that most fleeting of moments, they see the beauty and delicacy of our homeworld. It’s clearly not a view that many of us will get to experience in person, certainly not for the foreseeable future at least.

Despite that, thanks to some incredible photography and imaging techniques we too can view Earth from space and get a sense of our place in the solar system and the wider universe. 

The term ‘Big Blue Marble’ as it applies to Earth refers to an image captured of our planet by the Apollo 17 astronauts in December 1972. The image — officially designated as AS17–148–22727 by NASA— was taken at 29 thousand kilometres above the Earth by the crew of the spacecraft as it headed to the Moon.

Turning their view back on our planet, the astronomers caught a stunning image of the Mediterranean Sea to Antarctica. The image shows the south hemisphere heavily shrouded by clouds and represents the first time that an Apollo craft had been able to capture the southern polar ice caps.

The original uncropped AS17–148–22727 from which 'the Blue Marble' is taken. (NASA/Apollo 17 crew)
The original uncropped AS17–148–22727 from which ‘the Blue Marble’ is taken. (NASA/Apollo 17 crew)

Perhaps the most extraordinary thing about AS17-148-22727 is that it wasn’t supposed to exist. The crew weren’t scheduled to take an image at that point in their journey.

The fact that the photo was snapped very much during a ‘stolen moment’ aboard the craft and during a mission that was tightly scheduled down to the minute, makes the fleeting beauty it presents even more striking, as too does the fact that no human since has travelled far enough away from the surface of the planet to take such an image.

Since being taken ‘the Blue Marble’ has rightfully become one of the most reproduced images in human history. Though the most famous image of Earth from a space-based vantage point and a rare example of the glimpse of a fully illuminated globe, AS17–148–22727 is just one of a cavalcade of stunning images of our planet taken over seven decades.

The very first of these images were captured in perhaps the most unusual and ironic of circumstances. 

The Early days of Earth Photography: Recovering from War

“Consider again that dot [Earth]. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every ‘superstar,’ every ‘supreme leader,’ every saint and sinner in the history of our species lived there – on a mote of dust suspended in a sunbeam.”

Carl Sagan, Pale Blue Dot: A Vision of the Human Future in Space
The first image of Earth taken from space in 1946 (White Sands Missile Range / Applied Physics Laboratory)

During the Second World War German V2s caused untold amounts of damage upon the cities of Europe, raining death from the skies and bringing profound fear and sorrow. It’s somewhat ironic then that the scientific marvel of the first image of Earth from space was delivered by one of these fearsome rockets.

Several V2s– Vergeltungswaffe 2, the world’s first long-range guided ballistic missiles–had been reclaimed by the United States as part of Operation Paperclip. The aim, however, was to use their incredible supersonic speed not to escape radar detection, as had been the case during the war, but to escape the confines of the atmosphere.

The rockets had their explosive payloads removed from their nosecones and replaced with scientific equipment.

On 24th October 1946, experiments with the V2s would result in a tangible benefit and a legitimate scientific breakthrough. A rocket launched from the White Sands Missile Range in New Mexico, USA, would capture an image of the Earth from an altitude of 105km. Up until this point in time, the highest an image of earth that had been taken was 22km by equipment aboard a high-altitude balloon.

The image was captured by a 35mm camera in the device’s nosecone which was set to capture a picture every 1.5 seconds. These images were then dropped back to earth in a steel canister and developed.

(White Sands Missile Range / Applied Physics Laboratory)

The V2 program and the series of experiments that it birthed would help US scientists lay the groundwork for future space exploration and was reflected by similar experiments in the Soviet Union at the time. These programs and the reclamation of German technology and the scientists behind it was responsible for launching the space race of the 1950s and 1960s. And no goal or aspiration would encompass this heated scientific battle more than the desire to put a human on the Moon.

The Earth and the Moon: Picturing a Perfect Partnership

“Orbiting Earth in the spaceship, I saw how beautiful our planet is. People, let us preserve and increase this beauty, not destroy it!”

Yuri Gagarin, the first human in space (12 April 1961)
A view of the Earth from the Moon taken by NASA’s Lunar Orbiter 1 in 1966 (NASA/ LOIRP).

By 1966 when the image above was captured the space race was in full swing. The USSR had launched both Sputnik 1 & 2 into orbit in October and November 1957 respectively, with the first becoming the original Earth-orbiting satellite and the second carrying a dog named Laika into space.

This would quickly be followed by US satellites Explorer 1 carrying experimental equipment that would lead to the discovery of the Van Allen radiation belt, and the world’s first communications satellite SCORE, both in 1958. In the same year, the National Aeronautics and Space Administration (NASA) would be created to replace the National Advisory Committee on Aeronautics (NACA).

Earth rises above the Moon’s horizon as seen by Apollo 11 (NASA/ JSC)


Most significantly, in 1961 the Soviets would put the first human being into orbit. Cosmonaut Yuri Gagarin made a single orbit around the Earth at a speed of over 27 thousand kilometres per hour during his 108-minute stay in space.

Yet, it wasn’t the Soviets that captured the stunning image above of earth from the vicinity of the Moon’s surface. That honour belongs to the US craft Lunar Orbiter 1 (LU-A). The NASA spacecraft was the first US mission to orbit the Moon, its primary task was to photograph not the Earth but rather potential landing sites on the Moon for the upcoming Apollo missions.

Again, as was the case with Apollo 17’s ‘Blue Marble’, the image of Earth from space taken by Lu-A taken on August 28th 1966 by the onboard Eastman Kodak imaging system was completely unplanned.

In 1969 many of the Apollo missions themselves would capture stunning and evocative images of the Earth rising above the crest of the Moon’s surface–including the above image captured by Apollo 11 and the one below taken by Apollo 8. These ‘Earthrise’ photographs would become a popular expression of Earth’s relative isolation and vulnerability.

NASA’s Lunar Reconnaissance Orbiter (LRO) captured a unique view of Earth from the spacecraft’s vantage point in orbit around the moon on October 12, 2015. (NASA/ Goddard/ Arizona State University).

The Earth From the Surface of an Alien World

“The vast loneliness is awe-inspiring and it makes you realize just what you have back there on Earth.” 

Jim Lovell, Apollo 8 Command Module Pilot, during a live broadcast from the Moon on Christmas Eve 1968.

It’s no great surprise given our advancing exploration of space that our attention has turned to the view of Earth from other alien worlds. Even though we are still capturing amazing images from that vantage point such as the one above taken by NASA’s Lunar Reconnaissance Orbiter mission in 2015, our horizons have also broadened to a view of our homeworld from the surface of more distant worlds.

The first image ever taken of Earth from the surface of a planet beyond the Moon. It was taken by the Mars Exploration Rover Spirit (NASA/JPL/Cornell/Texas A&M)

The first image of earth taken from another planet (above) was captured by the Mars Exploration Rover Spirit on the 63rd Martian day of its mission in 2004. Earth was only visible in the image–comprised from images taken by the now silent robotic rover’s four panoramic cameras–after all the colour filters were removed.

This was followed up in January 2014 by NASA’s Curiosity Rover when it captured its first glimpse of Earth from the surface of Mars.

NASA’s Mars rover Curiosity took this photo of Earth from the surface of Mars on Jan. 31, 2014, 40 minutes after local sunset, using the left-eye camera on its mast. Inset: A zoomed-in view of the Earth and moon in the image. (NASA/JPL-Caltech/MSSS/TAMU)

Whilst Mars Exploration Rover Spirit and the Curiosity Rover images may not be the most visually spectacular in the catalogue built during seven decades of space exploration, it stands as a testament to man’s determination to explore other worlds. a determination that nows carries us beyond the solar system.


This composite image of Earth and its moon, as seen from Mars, combines the best Earth image with the best moon image from four sets of images acquired on Nov. 20, 2016, by the High Resolution Imaging Science Experiment (HiRISE) camera on NASA’s Mars Reconnaissance Orbiter. (NASA/JPL-Caltech/Univ. of Arizona)

A View on the Future

“You develop an instant global consciousness, a people orientation, an intense dissatisfaction with the state of the world, and a compulsion to do something about it. From out there on the moon, international politics look so petty. You want to grab a politician by the scruff of the neck and drag him a quarter of a million miles out and say, ‘Look at that, you son of a bitch!’ “

Edgar Mitchell, Apollo 14 astronaut and the sixth person to walk on the Moon.
Deep Space Climate Observatory (DSCOVR)

As we continue to expand our view of the Universe studying cosmic bodies further and further from our own solar system, the history of space photography reminds us that it is vital we keep a view on our own planet, too. It’s a testament to our scientific progress that the hardest element about putting together a brief article about images of Earth from space that it involved sifting through thousands of incredible pictures.

Currently, NASA’s fleet of satellites consists of many craft devoted to the observation of Earth from space. Often this observation from a cosmic vantage point has the benefit of providing perspective on the damage we are doing to our world. Not only this but NASA’s continued observation of our world allows us to better understand weather patterns and mitigate potential disasters.

Humanity has never been in a better position to understand our world and its place within the wider Universe. The view of our planet from space has shown us its fragility, vulnerability, and the lengths we must go to preserve this beautiful blue marble.

“It is crystal clear from up here that everything is finite on this little blue marble in a black space, and there is no planet B.”

Alexander Gerst, European Space Agency astronaut, to world leaders live from the ISS, December 17th 2018.

An artist's conception of HD 209458 b, an exoplanet whose atmosphere is being torn off at more than 35,000 km/hour by the radiation of its close-by parent star. This hot Jupiter was the first alien world discovered via the transit method, and the first planet to have its atmosphere studied. [NASA/European Space Agency/Alfred Vidal-Madjar (Institut d'Astrophysique de Paris, CNRS)]

Stellar flares can strip away the atmosphere of planets, make them less habitable

As humanity continues to explore planets beyond the solar system — exoplanets — investigations into conditions on these worlds become increasingly complex. This includes the question of whether these exoplanets can support life. 

New research has identified which stars would be most likely to host planets with the necessary conditions for habitability, based upon that star’s stellar activity and crucially the rate at which such activity strips away a planet’s atmosphere. 

“We wanted to figure out how planets lose their atmospheres from extreme ultraviolet radiation and estimate their impact on their potential to host life,” Dimitra Atri, a researcher from the Space Science at NYU Abu Dhabi (NYUAD), tells ZME Science. “We focused on a channel of escape called hydrodynamic escape where stellar radiation heats up the planet’s atmosphere and a part of it escapes into space.”

An artist's conception of HD 209458 b, an exoplanet whose atmosphere is being torn off at more than 35,000 km/hour by the radiation of its close-by parent star. This hot Jupiter was the first alien world discovered via the transit method, and the first planet to have its atmosphere studied. [NASA/European Space Agency/Alfred Vidal-Madjar (Institut d'Astrophysique de Paris, CNRS)]
An artist’s conception of HD 209458 b, an exoplanet whose atmosphere is being torn off at more than 35,000 km/hour by the radiation of its close-by parent star. This hot Jupiter was the first alien world discovered via the transit method, and the first planet to have its atmosphere studied. [NASA/European Space Agency/Alfred Vidal-Madjar (Institut d’Astrophysique de Paris, CNRS)]

Atri is the author of a paper published in the journal Monthly Notices of Royal Astronomical Society: Letters, which analyzes flare emissions using data collected by NASA’s Transiting Exoplanet Survey Satellite (TESS) observatory ultimately helping to determine where else in the Universe life is most likely to prosper.

Harbouring Life: A Question of Water Retention

Planet habitability is closely associated with that world’s ability to hold liquid water. That means that factors which can boil away that water or cause it to be lost to space reduce that habitability. The habitable zone of a star’s environment is defined as the range at which a planet can orbit and still possess liquid water. This means not too hot or too cold — criteria that led to the alternative name for such regions, the Goldilocks zone.

Yet, distance and a star’s luminosity are not the only factors which can affect a planet’s ability to hold liquid water. Space weather — including solar flares — is another determining element, one that as of yet is not well understood. “Flares erode planetary atmospheres,” Atri says. “A substantial atmosphere is needed to sustain liquid water on a planet’s surface. Flares reduce those chances and make planets less habitable.”

Betelgeuse a type H 1-2 star similar to those Atri found jettison frequent XUV flares which can strip an exoplanet’s atmosphere reducing conditions for habitability (NASA/SDO)

What Atri, alongside coauthor and graduate student Shane Carberry Mogan, discovered was that whilst luminosity from a star was still the primary driving factor in atmosphere stripping, flares were a more important factor for some stars than others. In particular, they discovered that flares from M0-M4 stars — cool, red stars like Betelgeuse — were more likely to strip an orbiting planet’s atmosphere. 

The duo determined that more frequent, lower energy flares in the extreme ultraviolet region (XUV) of the electromagnetic spectrum were more effective at stripping a planet’s atmosphere and thus reducing its habitability than less frequent, higher energy outbursts. XUV radiation strikes a planet’s atmosphere heating it. This causes hydrodynamic escape, pushing out light atoms first, which through collision and other drag effects also pull out heavier molecules. 

“We find that for most stars, luminosity-induced escape is the main loss mechanism, with a minor contribution from flares,” Atri explains. “However, flares dominate the loss mechanism of around 20 per cent of M4–M10 stars.

“M0–M4 stars are most likely to completely erode both their proto- and secondary atmospheres, whilst M4–M10 stars are least likely to erode secondary atmospheres.”

The study also highlights the fact that better modelling of the factors that affect an exoplanet’s atmosphere is needed. Determining the systems and planets most likely to harbour life will play an important factor in selecting targets for the upcoming James Webb Space Telescope — set to launch on October 31st 2021 — and the ESO’s Extremely Large Telescope (ELT) currently under construction in the Acatma desert, Chile. 

“The next research step would be to expand our data set to analyze stellar flares from a larger variety of stars to see the long-term effects of stellar activity, and to identify more potentially habitable exoplanets,” adds Atri.

The researcher also points out that the continued investigation of how planets lose their atmosphere could also focus on a target closer to home, our nearest neighbour, Mars. “Since it is extremely difficult to observe the escape process in exoplanets, we are planning to study this phenomenon in great detail on Mars with the UAE’s Hope mission,” the researcher says, explaining how observations from Mars missions can be used to better understand atmospheric escape and how this knowledge can be applied to exoplanets.“We will then apply our understanding of atmospheric escape to exoplanets and estimate the impact of extreme UV radiation on planetary habitability.”

An artist’s illustration of UAE’s Tess probe approaching the surface of Mars. Atri believes this investigation could yeild important data about exoplanet habitability.
(Mohammed bin Rashid Space Centre)

Further to the question of habitability, the study begins to address the wider question of the dynamics of stars and their planetary systems and the evolution of such arrangements. “Given the close proximity of exoplanets to host stars, it is vital to understand how space weather events tied to those stars can affect the habitability of the exoplanet,” Atri concludes. “Stars and planets are very tightly coupled in a number of ways and an improved understanding of this coupling are absolutely necessary to find habitable planets in our Galaxy and beyond.”

Atri. D., Carberry Morgan. S. R., [2020], ‘Stellar flares versus luminosity: XUV-induced atmospheric escape and planetary habitability,’ Monthly Notices of Royal Astronomical Society: Letters.

An artist's impression of a gravitational microlensing event by a free-floating planet. (Jan Skowron / Astronomical Observatory, University of Warsaw)

‘Lonely’ Rogue Planet Discovered Wandering the Milky Way

Researchers believe that our galaxy is teeming with cosmic orphans, planets wandering free of a parent star. Though common, these rogue planets are difficult to spot, especially when they are in the size range of the earth. 

Despite this difficulty; an international team of astronomers including Przemek Mróz, a postdoctoral scholar at the California Institute of Technology (Caltech) and Radosław Poleski from the Astronomical Observatory of the University of Warsaw, have spotted what they believe to be a free-floating planet with a size and mass somewhere in the range of Mars and Earth, wandering the Milky Way. 

The discovery represents a major step forward in the field of exoplanet investigation as it is the first earth-sized ‘rogue planet’ ever observed.

An artist's impression of a gravitational microlensing event by a free-floating planet. (Jan Skowron / Astronomical Observatory, University of Warsaw)
An artist’s impression of a gravitational microlensing event by a free-floating planet. (Jan Skowron / Astronomical Observatory, University of Warsaw)

“We found a planet that seems extremely lonely and small, far away in the Universe,” Poleski tells ZME Science. “If you can imagine, Earth is in a sandbox surrounded by lots of other planets, and light from the Sun. This planet isn’t. It’s truly alone.”

The rogue planet the team found — OGLE-2016-BLG-1928 — is believed to be the smallest free-floating planet ever discovered. It was found in data collected by Optical Gravitational Lensing Experiment (OGLE), a Polish astronomical project based at the University of Warsaw. Previously discovered rogues — such as the first-ever recorded free-floating planet also found by OGLE in 2016 — are closer in size to Jupiter.

The gravity of a free-floating planet may deflect and focus light from a distant star when passing close in front of it. Due to the distorted image, the star temporarily seems much brighter. (v)

“We discovered the smallest free-floating planet candidate to date. The planet is likely smaller than Earth, which is consistent with the predictions of planet-formation theories,” Mróz — lead author of the team’s study published in Astrophysical Journal Letters — explains to ZME Science. “Free-floating planets are too faint to be observed directly — we can detect them using gravitational microlensing via their light-bending gravity.”

The Gravity of the Situation

The team spotted this wandering planet using the technique of gravitational microlensing, often utilised to spot exoplanets — planets outside our solar system. Exoplanets can’t often be observed directly, and when they can it’s a result of interaction with radiation from their parent star — for example, the dimming effect exoplanets have when they cross in front of their star and block some of the light it emits. Clearly, as rogue planets don’t have a parent star, they don’t have these interactions, making micro-lensing events the only way of spotting them.

“Microlensing occurs when a lensing object — a free-floating planet or star — passes between an Earth-based observer and a distant source star, its gravity may deflect and focus light from the source,” Mróz explains to ZME Science. “The observer will measure a short brightening of the source star, which we call a gravitational microlensing event.”

When the gravity of a free-floating planet deflects and focuses light from a distant star, we can observe temporary changes in star brightness. (temporary changes in star brightness.
Credit: Jan Skowron / Astronomical Observatory, University of Warsaw.)

Mróz continues by explaining that the duration of microlensing events depends on the mass of the object acting as a gravitational lens. “The less massive the lens, the shorter the microlensing event. Most of the observed events, which typically last several days, are caused by stars,” Mróz says. “Microlensing events attributed to free-floating planets usually last barely a few hours which makes them difficult to spot. We need to very frequently observe the same part of the sky to spot brief brightenings caused by free-floating planets.”

Changes of brightness of the observed star during the gravitational microlensing event by a free-floating planet. (Credit: Jan Skowron / Astronomical Observatory, University of Warsaw/ Robert Lea)

By measuring the duration of a microlensing event and shape of its light curve astronomers can estimate the mass of the lensing object. That is how the team were able to ascertain this free-floating planet is approximately Earth-sized. “Hence, we can discover very dim objects, like black holes, or free-floating planets,” says Poleski. “We found it an event, which has a timescale of 41 minutes. And it’s the shortest event ever discovered.”

Poleski explains that the lack of any other lensing body in the system told the team that it is a very strong candidate for a free-floating planet. He adds: “We know it’s a planet because of the very short timescale and we think it’s free-floating because we don’t see any star next to it.”

Going Rogue. How Free-Floating Planets Come to Wander the Universe Alone

Astronomers believe that free-floating planets actually formed in protoplanetary disks around stars in the same way that ‘ordinary’ planets are. At some point, they are ejected from their parent planetary systems, probably after gravitational interactions with other bodies, for example, with other planets in the system.

“Some low-mass planets are expected to be ejected from their parent planetary systems during the early stages of planetary system formation,” says Mróz. “According to planet formation theories, most of the ejected planets should be smaller than Earth. Theories of planet formation predict that typical masses of ejected planets should be between 0.3 and 1.0 Earth masses. Thus, the properties of this event fit the theoretical expectations.”

These free-floating rogue planets are believed to be fairly common, but researchers can’t be certain because they are so difficult to spot. “Our current studies indicate that the frequency of low-mass–in the Earth to super-Earth-mass range–free-floating or wide-orbit planets is similar to that of stars — there are about two-five such objects per each star in the Milky Way,” says Mróz. “These numbers are very uncertain because they are based on a few sightings of short-timescale microlensing events. However, if free-floating/wide-orbit planets were less frequent than stars, we would have observed much fewer short-timescale events than we do.”

The researcher adds that though these objects are relatively common, the chances of observing microlensing events caused by them are still extremely small. “Three objects — source, lens, and observer — must be nearly perfectly aligned,” Mróz says. “If we observed only one source star, we would have to wait almost a million year to see the source being microlensed.”

In fact, one of the extraordinary elements of the team’s study is that such a short duration lensing event wasn’t believed to be observable given the sensitivity of the current generation of telescopes.

“The surprise, in general, was that with current technology we could define such a short time event,” Poleski says. “It’s especially surprising if you beat the previous record by a factor of few.”

The Nancy Grace Roman Telescope and Future Rogue Reconnaissance

For Mróz, there are still questions that he would like to see answered about OGLE-2016-BLG-1928. Primarily, confirming that it definitely is a free-floating planet. 

“We aren’t fully sure whether our planet is free-floating or not. Our observations rule out the presence of stellar companions within 10 astronomical units–930 million miles–of the planet, but the planet may have a more distant companion,” Mróz says. “Let’s imagine that we’re observing microlensing events by a doppelganger of the Solar System. If Jupiter or Saturn caused a microlensing event, we would see a signature of the Sun in the microlensing event light curve. However, microlensing events by Uranus or Neptune would likely look like those of free-floating planets, because they are very far from the Sun.”

Fortunately, Mróz says that should be possible to distinguish between free-floating and wide-orbit planets. “The lens is moving relative to the source star in the sky and — a few years after the microlensing event — the lens and source should separate in the sky,” the researcher elaborates. “If the lens has a stellar companion, we will see some excess of light at its position. If it is a free-floating planet, we will not.” 

Whilst this method may seem simple, Mróz says we cannot apply it now, because the existing telescopes are not powerful enough. This includes the instrument that conducted the long-term observations that gave rise to the OGLE sky survey–the data from which the team found the micro-lensing event OGLE-2016-BLG-1928.

“[The discovery of OGLE-2016-BLG-1928] was part of the larger search for microlensing events in general, which we perform in a number of steps,” Poleski tells ZME. “In one step, I started looking at the wide orbit planets — planets similar to Uranus, or Neptune and on similar orbits. And while looking for those, I screened a list of candidate microlensing events in general and I found this one.”

Soon NASA’s Nancy Grace Roman Telescope will take over the search for microlensing events, but in the meantime, there is still data from OGLE and other projects to be examined. “We now have more data and other surveys are also collecting data. So we hope to analyze those,” Poleski says. “The longer-term future is the launch of the Nancy Grace Roman Space Telescope. It will be a telescope similar to the Hubble telescope, only with new infrared and infrared cameras and that camera field of view larger than the Hubble Space Telescope. 

“One of the main projects for the Raman telescope will be to observe galactic bulge in search for microlensing planets, including free-floating planets.”

Mroz, P., Poleski, R., Gould, A. et al., ‘A terrestrial-mass rogue planet candidate detected in the shortest-timescale microlensing event,’ Astrophysical Journal Letters, [2020] DOI: 10.3847/2041–8213/abbfad

Water Found on the Moon’s Sunlit Surface

Using the Stratospheric Observatory for Infrared Astronomy (SOFIA) NASA researchers have made a stunning discovery regarding the Moon, finding that water is present on the natural satellite’s dayside, as well as its colder nightside. Hydrogen traces had previously been found at the lunar south pole, which experiences near-constant sunlight, but researchers did not believe this was related to water molecules.

This illustration highlights the Moon’s Clavius Crater with an illustration depicting water trapped in the lunar soil there, along with an image of NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) that found sunlit lunar water. (Credits: NASA)
This illustration highlights the Moon’s Clavius Crater with an illustration depicting water trapped in the lunar soil there, along with an image of NASA’s Stratospheric Observatory for Infrared Astronomy (SOFIA) that found sunlit lunar water. (Credits: NASA)

At a virtual press conference researchers Paul Hertz, Astrophysics Division director at NASA Headquarters, Washington, Jacob Bleacher, chief exploration scientist for the Human Exploration and Operations Mission Directorate at NASA Headquarters, Casey Honniball, a postdoctoral fellow at NASA’s Goddard Space Flight Center, Greenbelt, Maryland, and Naseem Rangwala, project scientist for the SOFIA mission, NASA’s Ames Research Center, Silicon Valley, California, discussed the findings with journalists from across the globe.

“We had indications that H2O – the familiar water we know – might be present on the sunlit side of the Moon,” says Hertz.  “Now we know it is there. This discovery challenges our understanding of the lunar surface and raises intriguing questions about resources relevant for deep space exploration.”

The team’s results could change our fundamental understanding of Earth’s largest natural satellite, and also how water forms and survives in the depths of space.

The findings are significant as previously NASA had believed that water could only be found on the Moon’s nightside and in deep cavernous craters, where it may be hard to reach. Scientists had believed that water of the sunlit side of the Moon would be boiled away as a result of the lack of atmosphere and from constant exposure to the sun.

Casey Honniball offers two possible explanations as to how this water found itself at the lunar south pole; suggesting that it could have been delivered by solar winds, or by micrometeorite impacts.

If the later is the case it could relate to two possible mechanisms. Not only could micrometeorites deliver water to the surface, but the heat from these impacts could also fuse together two hydroxyl molecules, thus creating a water molecule. If this is the case, the water is likely to be sealed within tiny glass beads, about the size of a pencil tip created by the immense heat of impact.

If the water is locked up in these glass beads, they would provide an excellent protective measure to prevent water from being lost to space or evaporating as a result of the Moon’s harsh conditions.

Scientists using NASA’s telescope on an airplane, the Stratospheric Observatory for Infrared Astronomy, discovered water on a sunlit surface of the Moon for the first time. SOFIA is a modified Boeing 747SP aircraft that allows astronomers to study the solar system and beyond in ways that are not possible with ground-based telescopes. Molecular water, H2O, was found in Clavius Crater, one of the largest craters visible from Earth in the Moon’s southern hemisphere. This discovery indicates that water may be distributed across the lunar surface, and not limited to cold, shadowed places.
Credits: NASA/Ames Research Center

How Much Water Have NASA Found?

Previous measurements of hydrogen signals from the moon’s sunlit side had been associated with hydroxyl molecules, which at a 3-micron scale at which observations were performed, is indistinguishable from water. SOFIA’s observation was conducted at an improved 6-micron resolution, thus allowing astronomers to confirm the presence of water.

“Prior to the SOFIA observations, we knew there was some kind of hydration,” says Honniball, the lead author who published the results from her graduate thesis work at the University of Hawaii at Mānoa in Honolulu. “But we didn’t know how much, if any, was actually water molecules – like we drink every day – or something more like drain cleaner.

“Water has a distinct chemical fingerprint at 6 microns that hydroxyl does not have.”

Naseem Rangwala points out the amounts of water found, equivalent to roughly a 12oz bottle of water in a cubic meter, is extremely spread out.

Whilst the observations are only of the Moon’s surface, if the water is contained in glass beads then it is expected that these beads could find their way deeper beneath the lunar surface.

SOFIA will now conduct follow-up observations looking for water in additional sunlit locations and during different lunar phases to learn more about how the water is produced, stored, and moved across the Moon. 

SOFIA–So Good

SOFIA is the world’s largest airborne observatory, a modified 747 that cruises high in the Earth’s stratosphere. From an altitude of 38,000 — 40,000 feet SOFIA’s onboard 2.7-meter (106-inch) reflecting telescope is able to capture a clear view of the Universe and objects in the solar system in the infrared spectrum, untroubled by the obscuring effect of 99% of the atmosphere’s water vapour. It is this unobscured view that has allowed it to capture data that led to this astounding new discovery about water on the Moon.

SOFIA-- here seen soaring over the snow-covered Sierra Nevada mountains with its telescope door open during a test flight--has allowed NASA to make a major new moon discovery. SOFIA is a modified Boeing 747SP aircraft. (NASA/Jim Ross)
SOFIA– here seen soaring over the snow-covered Sierra Nevada mountains with its telescope door open during a test flight–has allowed NASA to make a major new moon discovery. SOFIA is a modified Boeing 747SP aircraft. (NASA/Jim Ross)

SOFIA’s main purpose is to observe the Universe in the infrared spectrum, spotting objects and events that aren’t observable in visible light. The fact that it is mounted aboard a modified 747 means it can make observations from any point on Earth, a feature that has made it particularly useful for spotting transient events. This includes eclipse–like occurrences of Pluto, Titan–a moon of Saturn, and MU69–a Kuiper belt object also known as Arrokoth, which earned the nickname the ‘space snowman’ due to its bowling pin-like shape.

What is astounding about SOFIA’s observation is that it was made during a test of the telescope as the renovated 747 flew over the Nevada Desert on its way back to its home base in California. The telescope itself isn’t usually used to view relatively bright objects such as the Moon. Instead, it would usually be used to observed dim objects such as black holes, star clusters, and distant galaxies.

“It was, in fact, the first time SOFIA has looked at the Moon, and we weren’t even completely sure if we would get reliable data, but questions about the Moon’s water compelled us to try,” says Rangwala, SOFIA’s project scientist at NASA’s Ames Research Center in California’s Silicon Valley. “It’s incredible that this discovery came out of what was essentially a test, and now that we know we can do this, we’re planning more flights to do more observations.”


Water, Water, Everywhere. But is there a drop to drink?

This new discovery contributes to NASA’s efforts to learn about more about the Moon, in the process supporting its goal of deep space exploration. The big question is how accessible is this water and can it be used by a future mission?

In this multi-temporal illumination map of the lunar south pole, where the team has discovered the telltale fingerprint of water molecules. Shackleton crater (19 km diameter) is in the centre, the south pole is located approximately at 9 o’clock on its rim. The map was created from images from the camera aboard the Lunar Reconnaissance Orbiter.
Credits: NASA/GSFC/Arizona State University


The researchers are clear that answering many of these remaining questions will require getting down to the surface of the Moon The data collected by SOFIA will be of use to these surface mission, particularly for the future NASA mission  Volatiles Investigating Polar Exploration Rover (VIPER). VIPER will take to the surface of the Moon to create a water resource map of its surface, which can then be used by future missions.

“Water is a valuable resource, for both scientific purposes and for use by our explorers,” explains Bleacher. “If we can use the resources at the Moon, then we can carry less water and more equipment to help enable new scientific discoveries.”

If water can be mined from the Moon, it could fulfil a variety of use, including the synthesis of oxygen for astronauts, and even the creation of fuel. Understanding what form the water is in is key to understanding how to extract it.

“Finding water that is easier to reach is important to us,” says Bleacher. “If it is locked up in glass beads it may take more energy to retrieve than if it locked up in the soil.” That means NASA will be looking to discover what state the water is in.

All this comes ahead of NASA’s 2024 Artemis program which will see the first woman and the next man sent to the lunar surface. This will be in preparation for NASA’s next major goal, human exploration of Mars, which could begin as early as the 2030s.

In addition to these practical applications for future space exploration, a deeper understanding of the Moon enables astronomers, cosmologists, and astrophysicists to piece together a better picture of the broader history of the inner solar system and the possibility of water existing deeper in space.

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Artist’s impression of star being tidally disrupted by a supermassive black hole

Death By Spaghettification! Astronomers Spot a Star Being Consumed by a Black Hole

An international team of researchers has used telescopes from around the world — including instruments operated by the European Southern Observatory (ESO) — to glimpse a blast of light emitted by a star as it is torn apart by the tidal forces of a supermassive black hole

The event — technically known as a ‘tidal disruption event’ (TDE) — occurred 215-million light-years from Earth, but despite this intimidating sounding distance, this is the closest to our planet such a flare has ever been captured. This, and the fact the astronomers spotted the event early, means the team was able to study the phenomena in unprecedented detail, in turn uncovering some surprises in this violent and powerful process. 

Artist’s impression of star being tidally disrupted by a supermassive black hole
This illustration depicts a star (in the foreground) experiencing spaghettification as it’s sucked in by a supermassive black hole (in the background) during a ‘tidal disruption event’. In a new study, done with the help of ESO’s Very Large Telescope and ESO’s New Technology Telescope, a team of astronomers found that when a black hole devours a star, it can launch a powerful blast of material outwards. (ESO/M. Kornmesser)

The astronomers directed the ESO’s Very Large Telescope (VLT), based in the Atacama desert, Chile, and other instruments at a blast of light that first occurred last year. They studied the flare, located in AT2019qiz in a spiral galaxy in the constellation of Eridanus, for six months as it grew in luminosity and then faded. Their findings are published today in the Monthly Notices of the Royal Astronomical Society.

“My research focuses on close encounters between stars and supermassive black holes in the centres of galaxies. Gravity very close to a black hole is so strong that a star cannot survive, and instead gets ripped apart into thin streams of gas,” Thomas Wevers, co-author of the study and an ESO Fellow in Santiago, Chile, tells ZME Science. “This process is called a tidal disruption event, or sometimes ‘spaghettification’. 

“If not for such tidal disruption events, we would not be able to see these black holes. Hence, they provide a unique opportunity to study the properties of these ‘hidden’ black holes in detail.”

Thomas Wevers, ESO Fellow

Catching the Start of the Movie

Wevers, who was part of the Institute of Astronomy, University of Cambridge, UK, as the study was being conducted, explains that it can take several weeks — or even months — to identify these spaghettification events with any certainty. Such an identification also takes all the telescopes and observational power that can be mustered. This can often cause a delay that results in astronomers missing the early stages of the process.

This image shows the sky around the location of AT2019qiz, at the very centre of the frame. This picture was created from images in the Digitized Sky Survey 2. (ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin)

“It’s like watching a movie but starting 30 minutes in, a lot of information is lost if you can’t watch from the very beginning, and while you might be able to reconstruct roughly what has happened, you can never be completely sure,” the researcher explains. But, that wasn’t the case with this new event.

To stick to the analogy; this time the team had their popcorn and drink and were in their seats before the trailers started rolling. 

“In this new event, we were lucky enough to identify and hence observe it very quickly, which has allowed us to see and understand what happens in the early phases in great detail.”

Thomas Wevers, ESO Fellow

Spotting spaghettification events is not just difficult due to timing issues, though. Such events are fairly rare, with only 100 candidates identified thus far, and are often obscured by a curtain of dust and debris. When a black hole devours a star, a jet of material is launched outwards that can further obscure the view of astronomers. The prompt viewing of this event allowed that jet to be seen as it progressed. 

“The difficulty comes first from picking out these rare events in among all the more common things changing in the night sky: variable stars and supernova explosions,” Matt Nicholl, a lecturer and Royal Astronomical Society research fellow at the University of Birmingham, UK, and the lead author of the study tells ZME Science. “A second difficulty comes from the events themselves: they were predicted to look about 100 times hotter than the flare that we observed. Our data show that this is because of all the outflowing debris launched from the black hole: this absorbs the heat and cools down as it expands.”

Spaghettification: Delicious and Dangerous

The spaghettification process is one of the most fascinating aspects of black hole physics. It arises from the massive change in gravitational forces experienced by a body as it approaches a black hole. 

“A star is essentially a giant ball of hot, self-gravitating gas, which is why it is roughly spherical in shape. When the star approaches the black hole, gravity acts in a preferential direction, so the star gets squeezed in one direction but stretched in the perpendicular direction,” Wevers says. “You can compare it to a balloon: when you squeeze it between your hands, it elongates in the direction parallel to your hands. Because the gravity is so extreme, the result is that the star essentially gets squeezed into a very long and thin spaghetti strand — hence the name spaghettification.”


Death by Spagettification! (ESO/M. Kornmesser/ Robert Lea)

Nicholl continues, explaining what happens next to this stellar spaghetti strand: “Eventually, it wraps all the way around and collides with itself, and that’s when we start to see the light show as the material heats up before either falling into the black hole or being flung back into space.

“The distance at which the star encountered the supermassive black hole was around the same distance between the Earth and Sun — this shows how incredibly strong the gravitational pull of the black hole must be to be able to tear the star apart from that distance.”

“If you picture the Sun being torn into a thin stream and rushing towards us, that’s roughly what the black hole saw!”

Matt Nicholl, Royal Astronomical Society research fellow.

Suprises and Future Developments

The observations made by the astronomers have allowed them to study the dynamics of a star undergoing the spaghettification process in detail, something that hasn’t been possible before. And as is to be expected with such a first, the study yielded some surprises for the team. 

“The biggest surprise with this event was how rapidly the light brightened and faded,” Nicholl tells ZME. “It took about a month from the encounter for the flare to reach its peak brightness, which is one of the fastest we’ve ever seen.”

The researcher continues to explain that faster events are harder to find, so it suggests that there might be a whole population of short-lived flares that have been escaping astronomers’ attention. “Our research may have solved a major and long-standing mystery of why these events are 100 times colder than expected — in this event, it was the outflowing gas that allowed it to cool down.”

Confirming this idea means that the team must now seek scarce telescope time to investigate more of these events to see if this characteristic is unique to the AT2019qiz flare, or if it is a common feature of such events. “Because we studied only one event, it is still unclear whether our results apply universally to all such tidal disruption events. So we need to repeat our experiment multiple times,” Wevers says. “Unfortunately, we are at the whims of nature and our ability to spot new TDEs. When we do, we will need to confirm the picture we have put forward or perhaps adapt it if we find different behaviour.”

The ESO’s Very Large Telescope (VLT) will play an important role in the identification and study of future ‘spaghettification’ events. (ESO Photo Ambassador Serge Brunier.)

Wevers concludes by highlighting the unique position he, Nicholl, and their team find themselves in by studying such rare and difficult to observe events and the objects that lie behind them. “We aren’t yet in the phase where we think we have mapped all the behaviour that occurs following these cataclysmic events, so while each new TDE helps us to answer outstanding questions, at the same time it also raises new questions.

“We find ourselves continually in a catch-22 like situation, which in this case is a good thing as it propels our research forward!” exclaims Wevers.  “I find it pretty amazing that we can study gargantuan black holes, weighing millions or even billions of times the mass of our sun, and which are located hundreds of millions of light-years away, in such detail with our telescopes.”

Original research: Nicholl. M., Wevers. T., Oates. S. R., et al, ‘An outflow powers the optical rise of the nearby, fast-evolving tidal disruption event AT2019qiz,’ Monthly Notices of the Royal Astronomical Society, [2020].

With the help of ESO’s Very Large Telescope (VLT), astronomers have found six galaxies lying around a supermassive black hole, the first time such a close grouping has been seen within the first billion years of the Universe. This artist’s impression shows the central black hole and the galaxies trapped in its gas web. The black hole, which together with the disc around it is known as quasar SDSS J103027.09+052455.0, shines brightly as it engulfs matter around it. (ESO/L. Calçada)

‘Cosmic Web’ of a Supermassive Black Hole Ensnares Six Galaxies

Astronomers have discovered a tremendous cosmic web in the early Universe. Trapped within its threads are six galaxies feeding gas to a central supermassive black hole. 

Astronomers have made a startling discovery in the early Universe: six galaxies suspended in the cosmic web of a supermassive black hole. The finding represents the first time such a grouping has been found when the Universe was young —  just under a billion years after the ‘Big Bang.’

The cosmic web with its suspended galaxies seems to conform to the theory that supermassive black holes grew to monstrous sizes thanks to the fact that they sat at the centre of web-like structures with gas and dust to feed them. 

“The title of our article  —  ‘Web of the Giant’ — may suggest the idea of the supermassive black hole as a giant black spider at the centre of the web, with that web providing both the trap and the path to carry the material that feeds the giant at the centre,” Marco Mignoli, an astronomer at the National Institute for Astrophysics (INAF) in Bologna, Italy, tells ZME Science. “The importance of our work is that we are the first group to discover the galaxies that inhabit the web.”

With the help of ESO’s Very Large Telescope (VLT), astronomers have found six galaxies lying around a supermassive black hole, the first time such a close grouping has been seen within the first billion years of the Universe. This artist’s impression shows the central black hole and the galaxies trapped in its cosmic web. The black hole, which together with the disc around it is known as quasar SDSS J103027.09+052455.0, shines brightly as it engulfs matter around it. (ESO/L. Calçada)

The new observation of these six faint galaxies trapped in a web of filament ‘threads’ comprised of hot gas, stars, and galaxies surrounding a supermassive black hole, was made with the aid of the ESO’s Very Large Telescope (VLT) and is described in a paper published in the journal Astronomy and Astrophysics.

As is only fitting for a supermassive black hole ‘spider’, the web in which it sits is of tremendous size —  300 times that of the Milky Way. “From this filamentous structure, the giant black hole is probably accumulating material that has allowed it to grow extremely fast, reaching one billion solar masses in less than a billion years,” Mignoli, author of the paper, adds. “The galaxies stand and grow where the filaments cross, and streams of gas —  available to fuel both the galaxies and the central supermassive black hole —  can flow along the filaments.”

Supermassive Black Hole Feeding in the Early Universe

The light from this cosmic web has traveled to us from a time when the Universe was just 0.9 billion years old. This represents not just a time at which the first generation of black holes have formed from collapsing stars, but also the point where the faster-growing of these black holes have grown to truly monstrous sizes.

https://youtu.be/BHRYrINUigE

The question of how supermassive black holes managed to grow so rapidly has puzzled scientists for decades, with researchers unable to detect exactly how these black holes could obtain so much ‘black hole fuel’ so quickly. The findings seem to provide an answer, suggesting that the cosmic web and the galaxies within it contain enough gas to quickly grow the central black hole into a supermassive giant. 

“[The study] provides confirmation of several theories, that these primordial supermassive black holes are found at the center of immense filamentous structures composed by hot gas and by galaxies that are actively forming stars,” Mignoli says. “Such structures — ‘cosmic webs’ —  can provide the necessary material for the central black hole to grow extremely fast.”

Whilst this isn’t the first time astronomers have spotted a ‘cosmic web’, it is the first time its been occupied by a supermassive black hole ‘spider’ at its heart. 

 “Similar, early large scale structures have already been found, but none with a supermassive black hole at their centre,” Roberto Gilli, an astronomer at INAF in Bologna and co-author of the study, tells ZME Science. “Our work has placed an important piece in the largely incomplete puzzle that is the formation and growth of such extreme, yet relatively abundant objects so quickly after the Big Bang.”

What the researchers can’t be so sure of is how these black holes initially formed, the process by which they are ‘fed’, or how the cosmic web itself developed. “We have no observational evidence of from which seeds these giant black holes are grown,” Mignoli explains. “The structures are too far away, the gas flows too faint to be detected. And also from a theoretical point of view, there are problems that are too difficult to solve.”

One possibility is that cosmic webs such as that discovered by the team formed as a result of the gravitational influence of dark matter haloes. These bunches of mysterious substance — which makes up 90% of the matter in the known Universe — could have drawn together tremendous amounts of gas in the early Universe. From there, the gas and dark matter may have formed the matrix of a cosmic web. 

Mignoli explains that one of the most intriguing lingering questions is what process allows material to be transported from an intergalactic scale to the size of a black hole’s accretion disc — in the order of parsecs. 

Gilli offers some suggestions regarding this feeding process, albeit ones that are currently unsupported by observations: “According to theory, dense environments are a necessary but not sufficient condition,” Gilli explains. “[The feeding mechanism] could be related to gas availability in these dense regions: large reservoirs mean that there is enough gas to fuel the BH and grow fast. Some theories propose that direct gas streams through the web can fall directly into the black holes and grow them.”

Gilli also adds that another way by which supermassive black holes could gather tremendous mass is via galactic mergers. And, the researcher adds, the cosmic web could play a role in this process too. “Another way this web can aid black hole growth is through galaxy mergers: within these dense, filamentary environments, mergers of gas-rich galaxies are more frequent, and mergers normally destabilize gas within galaxies and allow it to fall within the black holes at their centres.”

Spider Hunting: Searching the Universe for more ‘Occupied’ Cosmic Webs

The galaxies observed by the team are some of the faintest ever studied by astronomers, and required employing the tremendous power of the VLT — located at the ESO’s Paranal Observatory in the Atacama Desert, Chile — for several hours. Thus, with the aid of the VLT’s MUSE and FORS2 instruments, the team was able to confirm the six galaxies were linked to a central supermassive black hole.

“Early supermassive black holes are among the most challenging systems in extragalactic astrophysics,” Gilli explains. “We designed this experiment more than 8 years ago in the hope of confirming theory expectations. Observations of such systems are painful and only by cumulating several years of effort we could finally confirm the existence of such a structure.”#

This image shows the sky around SDSS J103027.09+052455.0, a quasar powered by a supermassive black hole surrounded by at least six galaxies. This picture was created from images in the Digitized Sky Survey 2. (ESO/Digitized Sky Survey 2. Acknowledgement: Davide De Martin)

The aim now is to find more examples of such structures, which Gilli believes should be fairly common in the early Universe. Perhaps then we can start to answer the questions that surround the formation and evolution of such events. 

“We’d like to confirm more structure like this and also to discover populations of SMBHs in the early Universe that should exist but are still missing from our census,” Gilli says. “There are billion-solar-mass black holes at galaxies’ centres and we still do not know where they come from. And there is even more mystery surrounding such systems in the early Universe.”

Mignoli. M., Gilli. R., Decarli. R., et al, [2020], ‘Web of the giant: Spectroscopic confirmation of a large-scale structure around the z=6.31 quasar SDSS J1030+0524,’ Astronomy and Astrophysics. 

Gallery of stellar winds around cool ageing stars, showing a variety of morphologies, including disks, cones, and spirals. The blue colour represents material that is coming towards you, red is material that is moving away from you. (L. Decin, ESO/ALMA)

How Stellar Winds of Dying Stars Are Shaped

New observations have revealed that stellar winds are not spherical as previously believed, but instead come in a variety of shapes that resemble those of planetary nebulae — created when a dying star explosively sheds its outer layers, which by a weird naming quirk actually have nothing to do with planets.  In fact, those winds could mark out the ‘molds’ by which planetary nebulae are shaped.

The discovery comes as a result of research conducted by a team of astronomers including Leen Decin, from the Institute of Astronomy, KU Leuven, and is detailed in a paper published today in the journal Science. “We noticed these winds are anything but symmetrical or round,” Decin says. “Some of them are actually quite similar in shape to planetary nebulae.”

Gallery of stellar winds around cool ageing stars, showing a variety of morphologies, including disks, cones, and spirals. The blue colour represents material that is coming towards you, red is material that is moving away from you. (L. Decin, ESO/ALMA)
Winds of red giant stars observed around Gamma Aquilae
[Credit: Decin et al., Science (2020)] (L. Decin, ESO/ALMA)

The team believes that this variety in stellar winds and planetary nebulae shape around dying stars are connected and a result of interactions with companion stars in binary pairings, or even from exoplanets in orbit around the stars. “The Sun — which will ultimately become a red giant — is as round as a billiard ball,” Decin explains. “So we wondered; how can such a star produce all these different shapes?”

The findings collected by the team could explain a long-standing mystery of planetary nebulae around stellar remnants like red dwarfs come in a variety of close-but-not-quite-spherical shapes. 

Planetary nebulae display such a wide range of complex shapes and structures that although the influence of binary companions has been suggested as a possible cause of this diverse range of asymmetric forms, the fact they can arise around stars with spherically symmetric stellar winds has, until now, remained unexplained.

The answer found by the team is that these winds aren’t symmetric at all and that the shape of the winds directly informs the shape of planetary nebulae. 

Dying Stars’ Companions are a Bad Influence

The observations of the stellar winds of 14 AGB stars using the Atacama Large Millimeter/submillimeter Array made by the team were so-detailed that they actually allowed the team to categorize the shapes of the stellar winds and planetary nebula. Some were disc-shaped, some contained spirals, and some were conical — a good indication that the shapes were not created randomly — but, none had spherical symmetry.

Gallery of stellar winds around cool ageing stars, showing a variety of morphologies,
including disks, cones, and spirals. The blue colour
represents
material that is coming towards you, red
is material that is moving away from you. (L. Decin, ESO/ALMA)

In fact, the team realized it was the presence of other low-mass stars or exoplanets in the vicinity of the primary star that was shaping the stellar wind and planetary nebula. Professor Decin is on hand to provide a useful and colorful analogy: “Just like how a spoon that you stir in a cup of coffee with some milk can create a spiral pattern, the companion sucks material towards it as it revolves around the star and shapes the stellar wind.”

Stellar winds are important to astronomers as they account for one of the main mechanisms by which stars lose mass. This mechanism becomes even more critical when attempting to understand the death throes of stars of similar sizes to the Sun and as their cores contract and the outer layers swell creating planetary nebulae — the other major contributor to mass-loss in aging stars. Discovering the role played by stellar companions in such a process is a surprise, to say the least. 

The stellar wind of R Aquilae resembles the structure of rose petals. (L. Decin, ESO/ALMA)

“All our observations can be explained by the fact that the stars have a companion,” says Decin. “Our findings change a lot. Since the complexity of stellar winds was not accounted for in the past, any previous mass-loss rate estimate of old stars could be wrong by up to a factor of 10.”

Following this discovery, the team will now research how it impacts other crucial characteristics involved in the life and death stars like the Sun. In the process, the team believes that their research will add more depth to our view of stars.

The Stellar winds around R Hydrae take a more conical shape (L. Decin, ESO/ALMA)

“We were very excited when we explored the first images,” adds co-author Miguel Montargès, also from KU Leuven. “Each star, which was only a number before, became an individual by itself. Now, to us, they have their own identity. “This is the magic of having high-precision observations: stars are no longer just points anymore.”

But, whilst we are on the subject of the future, the team says their findings have particular ramifications for the end of our own star.

Death Spiral: How the Sun Dies and What it Leaves Behind

The Sun is roughly halfway through its lifetime, with half its core hydrogen exhausted, meaning that in approximately 5 billion years it will start to die. For a star of the Sun’s mass, this means undergoing the transformation into a red giant.

For stars with masses greater than the Sun, the collapse of their core will spark a new lease of life, with the fusion of helium into heavier elements being kick-started by tremendous gravitational pressure, providing an outward force that halts the collapse.

The Sun, in contrast, will fade as its core cools, the planetary nebula will continue to expand outwards, ultimately resulting in a white dwarf surrounded by diffuse material that was once its outer layers. 

The team’s research gives us an idea of just what shape this planetary nebula will take, and how it will be crafted by the solar system’s largest planets. “Jupiter or even Saturn — because they have such a big mass — are going to influence whether the Sun spends its last millennia at the heart of a spiral, a butterfly, or any of the other entrancing shapes we see in planetary nebulae today,” Decin notes. 

“Our calculations now indicate that a weak spiral will form in the stellar wind of the old dying Sun.”

This NASA/ESA Hubble Space Telescope image shows the massive galaxy cluster MACSJ 1206. Embedded within the cluster are the distorted images of distant background galaxies, seen as arcs and smeared features. These distortions are caused by the dark matter in the cluster, whose gravity bends and magnifies the light from faraway galaxies, an effect called gravitational lensing. This phenomenon allows astronomers to study remote galaxies that would otherwise be too faint to see. (NASA, ESA, G. Caminha (University of Groningen), M. Meneghetti (Observatory of Astrophysics and Space Science of Bologna), P. Natarajan (Yale University), the CLASH team, and M. Kornmesser (ESA/Hubble))

Astronomers Investigate Dark Matter’s Missing Ingredient

Our understanding of dark matter and its behavior could be missing a key ingredient. More gravitational lensing, the curving of spacetime and light by massive objects, could lead to the perfect recipe to solve this cosmic mystery. 

Despite comprising anywhere between 70–90% of the Universe’s total mass and the fact that its gravitational influence literally prevents galaxies like the Milky Way from flying apart, science is still in the dark about dark matter

As researchers around the globe investigate the nature and composition of this elusive substance, a study published in the journal Science suggests that theories of dark matter could be missing a crucial ingredient, the lack of which has hampered our understanding of the matter that literally holds the galaxies together. 

The presence of something missing from our theories of dark matter and its behavior emerged from comparisons of observations of the dark matter concentrations in a sample of massive galaxy clusters and theoretical computer simulations of how dark matter should be distributed in such clusters. 

Astronomers measured the amount of gravitational lensing caused by this cluster to produce a detailed map of the distribution of dark matter in it. Dark matter is the invisible glue that keeps stars bound together inside a galaxy and makes up the bulk of the matter in the Universe. (NASA, ESA, G. Caminha (University of Groningen), M. Meneghetti  (Observatory of Astrophysics and Space Science of Bologna), P. Natarajan (Yale University), and the CLASH team.)


Using observations made by the Hubble Space Telescope and the Very Large Telescope (VLT) array in the Atacama Desert of northern Chile, a team of astronomers led by Massimo Meneghetti of the INAF-Observatory of Astrophysics and Space Science of Bologna in Italy have found that small-scale clusters of dark matter seem to cause lensing effects that are 10 times greater than previously believed.

“Galaxy clusters are ideal laboratories in which to study whether the numerical simulations of the Universe that are currently available reproduce well what we can infer from gravitational lensing,” says Meneghetti. “We have done a lot of testing of the data in this study, and we are sure that this mismatch indicates that some physical ingredient is missing either from the simulations or from our understanding of the nature of dark matter.”

Just Add Gravitational Lensing

The lensing that the team believes accounts for dark matter discrepancies is a factor of Einstein’s theory of general relativity which suggests that gravity is actually an effect that mass has on spacetime. The most common analogy given for this effect is the distortion created on a stretched rubber sheet when a bowling ball is placed on it.

This effect in space that results from a star or even a galaxy curving space and thus bending the path of light as it passes the object. Otherwise known as gravitational lensing it is commonly seen when a background object–which could be as small as a star or as large as a galaxy– moves in front of a foreground object and curves light from it giving it an apparent location in the sky. 

The gravitational lensing of a distant quasar by an intermediate body forms a double image seen by astronomers on Earth. (Lambourne. R, Relativity, Gravitation and Cosmology, Cambridge Press, 2010)

In extreme cases, where this lensing causes the paths of light to change in such a way that its arrival time at an observer is different, it can cause a background object to appear in the night sky at various different points. A beautiful example of this is an Einstein ring, where a single object appears multiple times forming a ring-like arrangement.

Because dark matter only interacts via gravity, ignoring even electromagnetic interactions — hence why it can’t be seen — gravitational lensing is currently the best way to infer its presence and map the location of dark matter clusters in galaxies.

 Returning to the ‘rubber sheet’ analogy from above, as you can imagine, a cannonball will make a more extreme ‘dent’ in the sheet than a bowling ball, which in turn makes a bigger dent than a golf ball. Likewise, the larger the cluster of dark matter — the greater the mass — the more extreme the curvature of space and therefore, light.

The gravitational microlensing effect results from the bending of space-time near an object of given mass that is predicted by Einstein’s general theory of relativity. An object, such as a star, crossing our line of sight to a more distant source star will affect the light from that star just like a lens, producing two close images whose total brightness is enhanced. If the lensing star is accompanied by a planet, one can (potentially) observe not only the principal effect from the star, but also a secondary, smaller effect resulting from perturbation by the planet. ( Beaulieu et al)

But now imagine what would happen if the bowling ball on the rubber sheet was surrounded by marbles. Though their individual distortions may be small, their cumulative effect could be considerable. The team believes this may be what is happening with smaller clusters of dark matter. These small scale clumps of dark matter enhance the overall distortion. In a way, this can be seen as a large lens with smaller lenses embedded within it.

Cooking Up A High-Fidelity Dark Matter Map

The team of astronomers was able to produce a high-fidelity dark matter map by using images taken by Hubble’s Wide Field Camera 3 and Advanced Camera Survey combined spectra data collected by The European Southern Observatory’s (ESO) VLT. Using this map, and focusing on three key clusters — MACS J1206.2–0847, MACS J0416.1–2403, and Abell S1063 — the researchers tracked the lensing distortions and from there traced out the amount of dark matter and how it is distributed.

This image from the NASA/ESA Hubble Space Telescope shows the galaxy cluster MACS J0416.1–2403. A team of researchers used almost 200 images of distant galaxies, whose light has been bent and magnified by this huge cluster, combined with the depth of Hubble data to measure the total mass and dark matter content of this cluster more precisely than ever before. (ESA/Hubble, NASA, HST Frontier Fields)

“The data from Hubble and the VLT provided excellent synergy,” says team member Piero Rosati, Università Degli Studi di Ferrara in Italy. “We were able to associate the galaxies with each cluster and estimate their distances.”

This led the team to the revelation that in addition to the dramatic arcs and elongated features of distant galaxies produced by each cluster’s gravitational lensing, the Hubble images also show something altogether unexpected–a number of smaller-scale arcs and distorted images nested near each cluster’s core, where the most massive galaxies reside.

The team thinks that these nested lenses are created by dense concentrations of matter at the center of individual cluster galaxies. They used follow-up spectroscopic observations to measure the velocity of the stars within these clusters and through a calculation method known as viral theorem, confirmed the masses of these clusters, and in turn, the amount of dark matter they contain. 

Abell S1063, a galaxy cluster, was observed by the NASA/ESA Hubble Space Telescope as part of the Frontier Fields programme. The huge mass of the cluster acts as a cosmic magnifying glass and enlarges even more distant galaxies, so they become bright enough for Hubble to see. (NASA, ESA, and J. Lotz (STScI))

This fusion of observations from these different sources allowed the team to identify dozens of background lensed galaxies that were imaged multiple times. The researchers then took this high-fidelity dark matter map and compared it to samples of simulated galaxy clusters with similar masses, located at roughly the same distances.

These simulated galaxy clusters did not show the same dark matter cluster concentrations — at least not on a small scale that is associated with individual cluster galaxies. 

The discovery of this disparity should help astronomers design better computer simulation models and thus develop a better understanding of how dark matter clusters. This improved understanding may ultimately lead to the discovery of what this abundant and dominant form of matter actually is. 


Original research: Meheghetti. M., Davoli. G., Bergamini. P., et al, ‘An excess of small-scale gravitational lenses observed in galaxy clusters,’ Science, [2020], 

GW Orionis, a triple star system with a peculiar inner region. Unlike the flat planet-forming discs we see around many stars, GW Orionis features a warped disc, deformed by the movements of the three stars at its centre. This composite image shows both the ALMA and SPHERE observations of the disc. (ESO/Exeter/Kraus et al., ALMA (ESO/NAOJ/NRAO))

Warped gas disc torn apart by three stars directly observed for the first time

Astronomers have discovered a spectacular first in terms of star clusters and planet-forming discs of gas, a system–GW Orionis–with a warped disc with torn out inner rings. The team believes that the disc’s odd shape –which defies the common view of a flat plane orbiting planets and gas discs–was created when the misalignment of the three stars at the centre of the disc caused it to fracture into distinct rings.

As well as being extraordinary in its own right, the astronomers believe that the warped disc could harbour exotic and strange exoplanets– not unlike Tatooine in Star Wars series– which formed within the inclined rings and are, for now, hidden from view.

“The idea that planets form in neatly-arranged, flat discs around young stars goes back to the 18th century and Kant and Laplace,” research team-leader Stefan Kraus, a professor of astrophysics at the University of Exeter in the UK, tells ZME Science. “Our images reveal an extreme case where the disc is not flat at all, but is warped and has a misaligned ring that has broken away from the disc.”

“‘Tatooine’ planets that orbit around 2 or 3 suns have already been envisioned by science fiction and some Tatooine exoplanets have already been found.  Here, we observe how such planets form and find that they can form on extreme, highly inclined orbits — in configurations that are completely different from the ‘neat’ arrangement observed in the Solar System.”

Stefan Kraus, professor of astrophysics, the University of Exeter
The left panel shows an artistic impression of the inner region of the GW Orionis disc, including the ring, which is based on the 3D shape reconstructed by the team. (ESO)

GW Orionis is Twisted

The team saw the warped shape of the system GW Orionis, which sits 1300 light-years from Earth in the constellation of Orion, in observations made by the Very Large Telescope (VLT) operated by European Southern Observatory (ESO), and the Atacama Large Millimeter/ submillimeter Array (ALMA) based in the Chilean desert. But, properly envisioning this shape and its cause meant studying the system for a staggering 11 years.

“The most important result from our study is that we can identify the cause for the misalignments and link it to the ’disc tearing’ effect that has been proposed by theorists 8 years ago, but has not been observed so far,” Kraus continues. “For this, it was essential to measure the orbital motion of the three stars that are in the centre of the system over their full 11-year orbital period. 

“We found that the three stars do not orbit in the same plane, but their orbits are misaligned with respect to each other and with respect to the disc.”

Stefan Kraus, professor of astrophysics, the University of Exeter
This animation allows the viewer to see the warped disc and the tilted ring of GW Orionis that was torn apart from it in spectacular detail. The animation is based on a computer model of the inner region of GW Orionis, provided by the team; they were able to reconstruct the 3D orbits of the stars and the 3D shape of the disc from the observational data.

“We have observed GW Orionis, a triple star system surrounded by a planet-forming disc, with several different telescopes including the VLT and ALMA. After observing the three stars for several years, our team was able to calculate the orbits very accurately,” team member Alison Young of the Universities of Exeter and Leicester tells ZME Science. “This data allowed us to build a detailed computer model of the system, which predicted that the disc would be bent and even torn to form a separate inner ring.”

“A couple of years later when we received the data back from the VLT and ALMA, the image of a disc bent and even torn to form a separate inner ring, were stunning.”

Alison Young of the Universities of Exeter and Leicester

A paper detailing their work is published in the journal Science.

ALMA, in which ESO is a partner, and the SPHERE instrument on ESO’s Very Large Telescope have imaged GW Orionis, a triple star system with a peculiar inner region. Unlike the flat planet-forming discs we see around many stars, GW Orionis features a warped disc, deformed by the movements of the three stars at its centre. This composite image shows both the ALMA and SPHERE observations of the disc. The ALMA image shows the disc’s ringed structure, with the innermost ring (part of which is visible as an oblong dot at the very centre of the image) separated from the rest of the disc. The SPHERE observations allowed astronomers to see for the first time the shadow of this innermost ring on the rest of the disc, which made it possible for them to reconstruct its warped shape. (ESO/Exeter/Kraus et al., ALMA (ESO/NAOJ/NRAO))
GW Orionis, a triple star system with a peculiar inner region. Unlike the flat planet-forming discs we see around many stars, GW Orionis features a warped disc, deformed by the movements of the three stars at its centre. This composite image shows both the ALMA and SPHERE observations of the disc. (ESO/Exeter/Kraus et al., ALMA (ESO/NAOJ/NRAO))

That Tears It! How GW Orionis got warped

The images of GW Orionis that the astronomers collected represent the first visualisation of disc-tearing ever captured by researchers. This tearing and the ‘warped’ effect it created marks this out as a planetary system exceptionally different from the solar system.

“The radial shadows in the VLT SPHERE image are clear evidence that the ring is tilted. To form a narrow shadow like this on the disc you need a fairly opaque ring of material that is at an angle to the disc surface blocking the starlight,” Young explains. “This result is consistent with some modelling done by members of the team which worked out the most likely orientations of the components of the system.”

A 3D model of GW Orionis, (Kraus et al. 2020 Science 371)
A 3D model of GW Orionis, (Kraus et al. 2020 Science 371)

“This system is unusual because the orbits of the three stars are misaligned, unlike the planets in the solar system they do not orbit in the same plane, and these stars host a large disc that is also tilted relative to their orbits,” Young continues. “We see all sorts of intriguing structures now in images of protoplanetary discs but this is the first direct evidence of the disc tearing effect.”

The observations also gave the researchers an idea of the vast scale of the GW Orionis disc.

“The ring harbours about 30 Earth masses of dust, which is likely sufficient for planet formation to occur in the ring.  Any planets formed within the misaligned ring will orbit the star on highly oblique orbits and we predict that many planets on oblique, wide-separation orbits will be discovered in future planet imaging surveys.”

Stefan Kraus, professor of astrophysics, the University of Exeter

As well as being able to reconstruct the torn disc of GW Orionis from the ALMA data in conjunction with data collected from several other telescopes, the team has been able to piece together the process by which this tearing likely occurred. They conclude that it could be a result of those three, misaligned stars. Something that initially came as a surprise to the astronomers.

“One very intriguing aspect of GW Orionis is that the orbits of the stars are strongly misaligned with respect to each other, and they are also strongly titled with respect to the large-scale disc. This wasn’t clear at the time when we started the study and became only apparent after monitoring the orbit motion for the full 11-years orbital period.”

Stefan Kraus, professor of astrophysics, the University of Exeter
This computer simulation shows the evolution of the GW Orionis system. The scientists believe the disc around the three stars in the system was initially flat, much like the planet-forming disc we see around many stars. Their simulation shows that the misalignment in the orbits of the three stars caused the disc around them to break into distinct rings, which is exactly what they see in the observations of the system. (Exeter/Kraus et al.)

Alison Young explains that because the disc surrounds three stars and the orbits of those stars are misaligned with respect to each other, the gravitational pull on the disc is not the same all the way around. This means that the gas and dust orbiting in the disc around all three stars feels a different force at different positions in the disc. This is what tears the disc apart into separate rings.

“Our study shows that the strong distortions observed in the disc– such as the warp and torn-away ring–can be explained by the conflicting gravitational pull from the 3 stars.  The key aspect is that the orbits are strongly misaligned with the disc.

Stefan Kraus, professor of astrophysics, the University of Exeter

How Warped Rings and Multiple Suns Effect Exoplanets

One interesting consequence of the warping of this gas and dust is that fact that it will wrap rings of material around any planets forming within it. This tearing also has a marked effect on these exoplanets’ orbits. This leads to conditions that would make the exoplanets in the GW Orionis system significantly different from planets in our own solar system.

“The planets in our solar system all have more-or-less aligned orbits. Any planets that form in the warped disc or misaligned ring could have highly inclined orbits,” says Young. “Further out, the disc is flatter and any planets that form there are likely to orbit in a similar plane to the disc. Of course, any planets that form in the GW Orionis system will also have three suns!”

Kraus points out that planets with oblique orbits have been identified before–particularly in the case of ‘Hot Jupiters’–planets with a mass and size comparable to the solar system’s largest planet, but that orbit closer to their star and transit across its face.

“Hot Jupiters orbit their stars very close in, and it is clear that they have not formed on the oblique orbits were we observe them.  Instead, they must have been moved onto these orbits through migration processes,” Kraus says. “We haven’t found yet any long-period planets on oblique orbits–comparable to Earth or Jupiter. However, our research shows that such planets could form in the torn-apart rings around multiple systems. 

“Given that about half of all stars are found in multiple systems, there could be a huge population of such long-period planets with high obliquity.”

Stefan Kraus, professor of astrophysics, the University of Exeter
This artists impression shows the orbit of the planet in the triple-star system HD 131399. Two of the stars are close together and the third, brighter component is orbited by a gas giant planet named HD 131399Ab.

Existing under the glare of three suns would make the planets in the GW Orionis system similar in some ways to an exoplanet discovered by astronomers from the University of Arizona in 2016.

The young exoplanet HD 131399Ab, 340 light-years from Earth in the constellation Centaurus, has a scorching hot temperature of around 580 C and exists in a state of constant daytime. It too has been compared to the planet of Tatooine from the Star Wars series. But Straus believes the planets in GW Orionis could be much cooler than this–or could alternate between cool and hot climates.

“Planets on such orbits could have stable atmospheric conditions, but would be ‘ice worlds’ with low temperatures on their surfaces,” Kraus says. “Planets that might have formed in the circumstellar/ circumbinary disc would experience extreme temperature variations, depending on where they are on their orbit. This should result in a strongly variable climate.”

Further Questions and Future Investigations: Delving Deeper into GW Orionis

Questions still remain about the GW Orionis system especially in light of research from another team who investigated the system with the ALMA telescope. This work-published in The Astrophysical Journal Letters earlier this year– suggests that our understanding of how the disc became warped is missing a vital component. “We think that the presence of a planet between these rings is needed to explain why the disc tore apart,” says Jiaqing Bi of the University of Victoria, Canada, lead author of a paper.

Speaking to ZME Science exclusively, Kraus addresses this earlier research: “This alternative scenario, where a yet-unseen planet located between the inner and middle ring might be the cause for the unusual disc shape, is more speculative, as such as planet has not been found yet,” the astrophysicist says. “Also, the paper’s authors had less information on the 3-dimensional shape of the disk as their ALMA observations had 6x lower solution and they did not have scattered-light images showing the shadows. Plus, they did not know the full orbits.”

Young continues by adding one future question regarding GW Orionis she would like to see answered also concerns the mechanism that caused the warping of the as and dust planet-forming disc.

“An important question we need to look at is how these systems came to be misaligned in the first place. Was the disc formed with the stars, did the material forming the disc arrive later, or did the system get disrupted at some point?”

Alison Young of the Universities of Exeter and Leicester

“Think of a star as a spinning top tilted at an angle,” the researcher suggests. “We want to find out how tilted the stars are so we can check whether a star’s tilt–or ‘spin axis’– matches the tilt of its disc, or if the stars in a binary or triple system have the same or different tilts.”

Some members of the team that made this discovery are currently developing a technique for measuring the spin axis of stars which could massively aid the understanding of how these systems formed.

An Upcoming survey conducted by the ALMA telescope array could help shed light on the motion of gas and dust in planet-forming discs such as that found in the GW Orionis system. (NSF/NRAO)
An Upcoming survey conducted by the ALMA telescope array could help shed light on the motion of gas and dust in planet-forming discs such as that found in the GW Orionis system. (NSF/NRAO)

Remembering that whilst this is not the first system discovered with such a warped disc, it is the first with a directly observed torn disc. This means the key to answering lingering questions likely lies in the direct observation of more systems that share features with GW Orionis.

“There are a few planet-forming discs that show some evidence of warping but for these, it is unclear what is causing the effect or there is an alternative scenario that can explain the observations, that has not been ruled out yet,” adds Young. “This is the first time that disc tearing has been directly observed and the only system so far for which we can link the structure with the physical mechanism behind it.”

Young suggests that the results of a larger survey performed by the ALMA array could provide clearer information about the motion of gas in planet-forming discs and their chemical composition, thus helping the team gather more information about the GW Orionis disc.

“We would like to obtain high-resolution observations of molecular emission from GW Orionis to shed more light on the motion of the gas in the disc and perhaps reveal any planets that are forming,” she explains. “Of course, we also are keen to understand if there are differences in how planets might form in warped discs compared to flat discs around a single star and we will be working on new computer models to look at this, using what we have learned from our observations.”

ALMA and SPHERE view of GW Orionis (side-by-side)
The ALMA image (left) shows the disc’s ringed structure, with the innermost ring separated from the rest of the disc. The SPHERE observations (right) allowed astronomers to see for the first time the shadow of this innermost ring on the rest of the disc, which made it possible for them to reconstruct its warped shape.

Young explains the importance of the GW Orionis images the team captured, whilst focusing on one image that for her, brought home the significance of the investigation in which she played a part.

“I find the SPHERE image [above left] in particular amazing because we can really see the disc is a 3-dimensional structure with a surface covered in bumps and shadows. We are looking at what could eventually become an unusual type of planetary system in the very process of forming.”

Alison Young of the Universities of Exeter and Leicester

For Stefan Kraus, the beauty of investigating a system such as GW Orionis is the wonder to imagining what it is like to stand on the surface of such a world and stare up into sky. Kraus concludes: “Half of the sky would be covered by a massive disc warp that is being illuminated by the 3 stars, intercepted by narrow shadows that are cast by the misaligned disc ring.”

“I find it fascinating to imagine how the sky would look like from any planet in such a system — one would see not only the 3 stars dancing around each other at different speeds but also a massive dust ring extending over the whole firmament.”

Stefan Kraus, professor of astrophysics, the University of Exeter
It's getting crowded up there. A plot of space debris around the Earth. (NASA)

Scientists spot space debris in daylight, helping satellites ‘social distance’

It’s really getting crowded up there! The immediate area around Earth is cluttered with space debris, with recent estimates suggesting almost 4,000 man-made satellites in a near-Earth orbit, only one-third of which are currently operational. These non-operational units are subject to leakage, fragmentation and even explosions — further littering the immediate region around our planet. On top of this is a further population of near 20,000 known space debris objects. 

If humanity is going to continue to exploit the space immediately surrounding the Earth measures need to be taken to avoid this space debris. Collisions between this space junk and operating satellites aren’t just costly and damaging, they also create more debris. Now researchers at the University of Bern have made a breakthrough that just might help satellites avoid just collisions. 

The Bern team used the geodesic laser at Optical Ground Station and Geodynamics Observatory Zimmerwald to spot space debris in the daylight. (© Universität Bern / Université de Bern / University of Bern, AIUB)
The Bern team used the geodesic laser at Optical Ground Station and Geodynamics Observatory Zimmerwald to spot space debris in the daylight. (© Universität Bern / Université de Bern / University of Bern, AIUB)

The Bern team is the first in the world to successfully determine the distance from Earth to a piece of space junk in daylight. The researchers performed the feat on June 24th using a geodesic laser fired from Swiss Optical Ground Station and Geodynamics Observatory Zimmerwald. The achievement opens up the possibility of spotting space debris during the day, this means that possible collisions between satellites and space debris can be identified early and mitigation strategies such as evasive manoeuvres can be implemented earlier. 

Being Evasive

Spotting space debris during the day should help prevent events such as the collision that occurred between the operational communications satellite Iridium 33 and the obsolete Cosmos 2251 communications satellite in 2009. Occurring at an altitude of 800 km over Siberia the impact at 11.7 km/s created a cloud of over 2000 pieces of debris — each larger than 10 cm in diameter. Within a matter of months, this cloud of debris had spread across a wide area, and it has been a threat to operational satellites ever since. 

Simulations performed at Lawrence Livermore National Lab on the Testbed Environment for Space Situational Awareness (TESSA) show the collision between Iridium 33 and the Cosmos 2251 communications satellite and the space debris it created. (Lawrence Livermore National Lab)

But one positive did come out of the event, it made both scientists and politicians wake-up to the fact that the problem of space debris can no longer be ignored.

In fact, the risk of collision with space junk in certain orbits around the Earth is so great, that evasive manoeuvres are commonplace. The ESA alone receives thousands of collision warnings for each satellite in its fleet per year! This leads to satellites performing dozens of evasive acts each year. But, it’s vitally important to accurately assess when evasive action is actually needed as they can be costly and time-consuming to perform. 

“The problem of so-called space debris — disused artificial objects in space — took on a new dimension,” says Professor Thomas Schildknecht, head of the Zimmerwald Observatory and deputy director of the Astronomical Institute at the University of Bern. “Unfortunately, the orbits of these disused satellites, launcher upper stages or fragments of collisions and explosions are not known with sufficient accuracy.”

Thus, as well as reducing collision risk, daytime observations of space debris could mean that unnecessary evasive action is avoided. There could be another benefit to early debris detection too. 

Many researchers are currently investigating the possibility of missions to clear space debris. One such example is the work of Antônio Delson Conceição de Jesus and Gabriel Luiz F. Santos, both from the State University of Feira de Santana, Bahia, Brazil, recently published in the journal EPJ Special Topics. The pair modelled the complex rendezvous manoeuvres that would be required to bring a ‘tug vehicle’ into contact with space junk. Better positioning debris clusters could assist these efforts considerably.

Fun with Lasers

Currently, the position of space debris can only be estimated with a precision of around a few hundred metres, but the team from Bern believe that using the satellite laser ranging method they employed to make their daylight measurement, this margin of error can be slashed down to just a few meters, a massive improvement in accuracy. 

“We have been using the technology at the Zimmerwald Observatory for years to measure objects equipped with special laser retroreflector,” Schildknecht says, adding that these measurements were also previously only possible to make at night. “Only a few observatories worldwide have succeeded in determining distances to space debris using special, powerful lasers to date.”

The Zimmerwald Laser and Astrometry Telescope ZIMLAT in Zimmerwald, which is used for distance measurement to space debris objects. (© Universität Bern / Université de Bern / University of Bern, AIUB)
Example of a “string of pearls” of photons reflected by the target debris object in the “sea of sky background photos”. (© Universität Bern / Université de Bern / University of Bern, AIUB)

Despite providing more accurate measurements, geodetic laser systems such as the one at the Zimmerwald observatory employed by the researchers are actually at least one order of magnitude less powerful than specialized space debris lasers. Additionally, detecting individual photons diffusely reflected by space debris amid the sea of daylight photons is no mean feat.

These problems were overcome by the use of highly sensitive scientific CMOS camera with real-time image processing to actively track the space junk, and a real-time digital filter to detect the photons reflected by the object.

“The possibility of observing during the day allows for the number of measures to be multiplied. There is a whole network of stations with geodetic lasers, which could in future help build up a highly precise space debris orbit catalogue,” Schildknecht concludes. “More accurate orbits will be essential in future to avoid collisions and improve safety and sustainability in space.”

Comet NEOWISE Comes into Focus for a Close-up

Time is running out to catch a glimpse of the comet NEOWISE. The comet — the brightest object to grace the skies over the Northern Hemisphere in 25 years — will soon disappear from view. At least as far as the naked eye is concerned. Fortunately, the Hubble Space Telescope is on hand to capture stunning images of the comet — discovered on March 27th by NASA’s Wide-field Infrared Survey Explorer (WISE) space telescope during its mission to search for near-Earth objects. 

Hubble Captures a stunning close-up Comet NEOWISE (NASA, ESA, Q. Zhang (California Institute of Technology), A. Pagan (STScI))
Hubble Captures a stunning close-up Comet NEOWISE (NASA, ESA, Q. Zhang (California Institute of Technology), A. Pagan (STScI))

The image taken by Hubble on 8th August — which represents the closest ever taken of the comet since it first lit up the sky — shows NEOWISE as it sweeps past the Sun. This is the first time that astronomers have managed to capture such a bright object as it passes our star.

Hubble snapped the object as it rapidly makes its way out of the solar system, with it not scheduled to return for 6,800 years. The comet caused a stir amongst amateur star watchers and the general public as it was visible with the naked eye under the right conditions.

“Nothing captures the imagination better than actually seeing its tails stretching into the sky in person,” Qicheng Zhang,  a graduate student studying planetary science at Caltech, Pasadena, CA, who has been heavily involved in the study of NEOWISE. “The comet last came around about 4,500 years ago. This was around when the Egyptian pyramids were being built.”

“My research area covers comets and their evolution under solar heating,” Zhang explains to ZME Science. “I also like to keep track of potentially bright comets to actually see in the sky, which included this particular comet.”

Colour image of the comet taken by Hubble on 8 August 2020 within the frame of a ground-based image of the comet that was taken from the Northern Hemisphere on 18 July 2020. (NASA, ESA, Q. Zhang (California Institute of Technology), A. Pagan (STScI), and Z. Levay)
Colour image of the comet taken by Hubble on 8 August 2020 within the frame of a ground-based image of the comet that was taken from the Northern Hemisphere on 18 July 2020. (NASA, ESA, Q. Zhang (California Institute of Technology), A. Pagan (STScI), and Z. Levay)

The image shows NEOWISE’s halo of glowing gas and dust illuminated by light from the Sun surrounding the icy nucleus of the comet, too small at little more than 4.8km across to be fully resolved by the telescope. In contrast, the dust halo that surrounds the comet’s heart is too large to be fully resolved by the space telescope, with its diameter measuring an estimated 18,000 km.

Zhang points out that as NEOWISE moves past the Sun, there is a chance we could still glimpse its icy core: “As the comet recedes from the Sun, the dust with clear and reveal the solid nucleus currently buried within, providing an opportunity to directly observe the source of all the activity that made the comet impressive last month.”

Let’s Stick Together: Why NEOWISE Survived and ATLAS Didn’t

Previous attempts to capture other bright comets as they pass the Sun have failed because these objects have disintegrated as they passed too close to the star. This break-up is driven by both the incredible heat of the Sun causing the icy heart of the comets to fragment, and the powerful gravitational influence of our star further pulling the comets apart. 

The most striking example of this came shortly after the discovery of NEOWISE, with the observation of the fragmentation of the comet ATLAS in April this year. The collapse of this comet — believed at the time to offer our best look at such an icy body — in 30 separate pieces was also caught by Hubble. 

ATLAS feels the heat. The comet, discovered in December 2019 breaks up under the intense heat and gravitational influence of the Sun ( NASA/ ESA/ STScI/ D. Jewitt (UCLA))
ATLAS feels the heat. The comet, discovered in December 2019 breaks up under the intense heat and gravitational influence of the Sun ( NASA/ ESA/ STScI/ D. Jewitt (UCLA))

Unlike comet ATLAS, itself only discovered in December 2019, comet NEOWISE somehow survived its close passage to the Sun–with its solid, icy nucleus able to withstand the blistering heat of the star– enabling Hubble to capture the comet in an intact state.

As the latest image of NEOWISE shows, however, it is not going to escape its encounter with the Sun completely unscathed. Jets can clearly be seen blasting out in opposite directions from the poles of the comet’s icy nucleus. These jets represent material being sublimated–turning straight from a solid to a gas skipping a liquid stage–beneath the surface of the comet. This ultimately results in cones of gas and dust erupting from the comet, broadening out as the move away from the main body, forming an almost fan-like shape.

This animation composed of three Hubble images of NEOWISE shows clearly jets of sublimated material erupting from the comet forming fan-like shapes. (NASA, ESA, Q. Zhang (California Institute of Technology), A. Pagan (STScI), and M. Kornmesser))

Far from being just a stunning image of a comet as it passes through the inner solar system, the Hubble images stand to teach astronomers much about NEOWISE and about comets in general.

“It’s a fairly large comet that approached closer to the Sun than the vast majority of comets of its size do,” Zhangs says. “These factors contributed to its high brightness and also made it a good candidate to see how solar heating alters comets, as the effects are theoretically amplified by its close approach to the Sun.

“That information is useful for interpreting observed characteristics of other comets that don’t approach as close to the Sun, and thus where the changes are more gradual and might not be directly observable.”

In particular, the colour of the comet’s dust halo, and the way it changes as NEOWISE moves away from the Sun, gives researchers a hint as to the effect of heat on such materials. This could, in-turn, help better determine the properties of the dust and gas that form what is known as the ‘coma’ around a comet.

“We took images to show the colour and polarization of the dust released by the comet, to get a sense of what it looks like before it’s broken down by sunlight,” says Zhang. “That analysis is ongoing–and will take a while to do properly–but as the published images show, we’ve caught at least a couple of jets carrying dust out from the rotating nucleus.”

The information contained in the Hubble data will become clearer as researchers delve deeper into it. But, the investigation of NEOWISE’s cometary counterparts will benefit from future telescope technological breakthroughs. This will include spotting comets much more quickly and thus, further out from the Sun.

“When this comet was discovered by the NEOWISE mission, it was only 3 months from its close approach to the Sun and had already begun ramping up activity,” Zhang says. “More sensitive surveys, like the upcoming Legacy Survey of Space and Time (LSST) at the Rubin Observatory, will allow us to find such comets much earlier before they become active, enabling us to track them throughout their apparition from beginning to end.

“This will facilitate a more precise comparison of what changes the comets undergo during their solar encounter.”

The next step in Zhang’s research, however, will be comparing the qualities of comet NEOWISE to other such objects, particularly a recent interstellar visitor to our solar system: “This is one of three comets I have observed or have planned to observe in this manner, the others being the interstellar comet 2I/Borisov and the distant solar system comet C/2017 K2 (PANSTARRS),” the researcher concludes. “My team of collaborators and I will be evaluating all three comets to see how their differences in present location and formation/dynamical history translate into differences in physical properties.”

This artist's conception illustrates a Jupiter-like planet alone in the dark of space, floating freely without a parent star. (NASA)

Rogue Planets Could Outnumber Stars in the Milky Way

Our galaxy is teeming with rogue planets either torn from their parent stars by chaotic conditions or born separate from a star. These orphan planets could be discovered en masse by an outcoming NASA project — Nancy Grace Roman Space Telescope. 

The Milky Way is home to a multitude of lonely drifting objects, galactic orphans — with a mass similar to that of a planet — separated from a parent star. These nomad planets freely drift through galaxies alone, thus challenging the commonly accepted image of planets orbiting a parent star. ‘Rogue planets’ could, in fact, outnumber stars in our galaxy, a new study published in the Astronomical Journal indicates. 

“Think about how crazy it is that there could be an Earth, a Mars, or a Jupiter floating all alone through the galaxy. You would have a perfect view of the night sky but stuck in an eternal night,” lead author of the study, Samson Johnson, an astronomy graduate student at The Ohio State University, tells ZME Science. “Although these planets could not host life, it is quite a place to travel to with your imagination. The possibility of rogue planets in our galaxy had not occurred to me until coming to Ohio State.”

This artist’s conception illustrates a Jupiter-like planet alone in the dark of space, floating freely without a parent star. (NASA)

Up to now, very few very of these orphan planets have actually been spotted by astronomers, but the authors’ simulations suggest that with the upcoming launch of NASA’s Nancy Grace Roman Space Telescope in the mid-2020s, this situation could change. Maybe, drastically so.

“We performed simulations of the upcoming Nancy Grace Roman Space Telescope (Roman) Galactic Exoplanet Survey to determine how sensitive it is to microlensing events caused by rogue planets,” Johnson says. “Roman will be good at detecting microlensing events from any type of ‘lens’ — whether it be a star or something else — because it has a large field of view and a high observational cadence.”

The team’s simulations showed that Roman could spot hundreds of these mysterious rogue planets, in the process, helping researchers identify how they came to wander the galaxy alone and indicating how great this population could be in the wider Universe.

Rogue by Name, Rogue by Nature: Mysterious and Missing

Thus far, much mystery surrounds the process that sees these planets freed from orbit around a star. The main two competing theories suggest that these stars either are thrown free of their parent star, or form in isolation. Each process would likely lead to rogue planets with radically different qualities. 

ESO’s New Technology Telescope at the La Silla Observatory captures the rogue planet CFBDSIR J214947.2-040308.9 in infrared light–appearing as a faint blue dot near the centre of the picture. This is the closest such object to the Solar System discovered thus far. (ESO/P. Delorme)

“The first idea suggests that rogue planets form like planets in the Solar System, condensing from the protoplanetary disk that accompanies stars when they are born,” Johnson explains. “But as the evolution of planetary systems can be chaotic and messy, members can be ejected from the system leading to most likely rogue planets with masses similar to Mars or Earth.”

 Johnson goes on to offer an alternative method of rogue planet formation that would see them form in isolation, similar to stars that form from giant collapsing gas clouds. “This formation process would likely produce objects with masses similar to Jupiter, roughly a few hundred times that of the Earth.”

“This likely can’t produce very low-mass planets — similar to the mass of the Earth. These almost certainly formed via the former process,” adds co-author Scott Gaudi, a professor of astronomy and distinguished university scholar at Ohio State. “The universe could be teeming with rogue planets and we wouldn’t even know it.”

The question is if these objects are so common, why have we spotted so few of them? “The difficulty with detecting rogue planets is that they emit essentially no light,” Gaudi explains. “Since detecting light from an object is the main tool astronomers use to find objects, rogue planets have been elusive.”

Astronomers can use a method called gravitational microlensing to spot rogue planets, but this method isn’t without its challenges, as Gaudi elucidates:

“Microlensing events are both unpredictable and exceedingly rare, and so one must monitor hundreds of millions of stars nearly continuously to detect these events,” the researcher tells ZME Science. “This requires looking at very dense stellar fields, such as those near the centre of our galaxy. It also requires a relatively large field of view.”

Additionally, as the centre of the Milky Way is highly obscured by requiring us to look at it in the near-infrared region of the electromagnetic spectrum — a task that is extremely difficult as the Earth’s atmosphere makes the sky extremely bright in near-infrared light.

“All of these points argue for a space-based, high angular resolution, wide-field, near-infrared telescope,” says Gaudi. “That’s where Roman — formally the Wide Field InfraRed Survey Telescope (WFIRST) — comes in.” 

Nancy Grace Roman Space Telescope (and Einstein) to the Rescue!

The Roman telescope — named after Nancy Grace Roman, NASA’s first chief astronomer, who paved the way for space telescopes focused on the broader universe–will launch in the mid-2020s. It is set to become the first telescope that will attempt a census of rogue planets — focusing on planets in the Milky Way, between our sun and the centre of our galaxy, thus, covering some 24,000 light-years.

An artist’s redition of the Nancy Grace Roman Space Telescope, named after ‘the Mother of Hubble’ (NASA)

The team’s study consisted of simulations created to discover just how sensitive the Roman telescope could be to the microlensing events that indicate the presence of rogue planets, finding in the process, that the next generation space telescope was 10 times as sensitive as current Earth-based telescopes. This difference in sensitivity came as a surprise to the researchers themselves. “Determining just how sensitive Roman is was a real shock,” Johnson says. “It might even be able to tell us about moons that are ejected from planetary systems! We also, found a new ‘microlensing degeneracy’ in the process of the study — the subject another paper that will be coming out shortly.”

Johnson’s co-author Gaudi echoes this surprise. “I was surprised that Roman was sensitive to rogue planets with mass as low as that of Mars and that the signals were so strong,” the researcher adds. “I did not expect that before we started the simulations.”

The phenomenon that Roman will exploit to make its observations stems from a prediction made in Einstein’s theory of general relativity, that suggests that objects with mass ‘warp’ the fabric of space around them. The most common analogy used to explain this phenomenon is ‘dents’ created in a stretched rubber sheet by placing objects of varying mass upon it. The heavier the object — thus the greater the mass — the larger the dent. 

This warping of space isn’t just responsible for the orbits of planets, it also curves the paths of light rays, the straight paths curving as they pass the ‘dents’ in space. This means that light from a background source is bent by the effect of the mass of a foreground object. The effect has recently been used to spot a distant Milky Way ‘look alike’. But in that case, and in the case of many gravitational lensing events, the intervening object was a galaxy, not a rogue planet, and thus was a much less subtle, more long-lasting, and thus less hard to detect effect than ‘microlensing’ caused by a rogue planet. 

This animation shows how gravitational microlensing can reveal island worlds. When an unseen rogue planet passes in front of a more distant star from our vantage point, light from the star bends as it passes through the warped space-time around the planet. The planet acts as a cosmic magnifying glass, amplifying the brightness of the background star. (NASA’s Goddard Space Flight Center/CI Lab)

“Essentially, a microlensing event happens when a foreground object — in this case, a rogue planet — comes into very close alignment with a background star. The gravity of the foreground object focuses light from the background star, causing it to be magnified,” Gaudi says. “The magnification increases as the foreground object comes into alignment with the background star, and then decreases as the foreground object moves away from the background star.”

As Johnson points out, microlensing is an important and exciting way to study exoplanets — planets outside the solar system — but when coupled with Roman, it becomes key to spotting planetary orphans.

“Roman really is our best bet to find these objects. The next best thing would be Roman 2.0 — with a larger field of view and higher cadence,” the researcher tells ZME, stating that rogue planets are just part of the bigger picture that this forthcoming space-based telescope could allow us to see. “I’m hoping to do as much work with Roman as possible. The next big project is determining what Roman will be able to teach us about the frequency of Earth-analogs — Earth-mass planets in the habitable zones of Sun-like stars.”

Original Research

Johnson. S. A., Penny. M, Gaudi. B. S, et al, ‘Predictions of the Nancy Grace Roman Space Telescope Galactic Exoplanet Survey. II. Free-floating Planet Detection Rates*,’ The Astronomical Journal, [2020].