It’s done: NASA’s team behind the James Webb Space Telescope successfully deployed its massive primary mirror, marking a big milestone in one of the most complicated missions in space. Now, the team will focus on directing the telescope to its final destination to explore every phase of cosmic history, but so far, so good.
The two winds of the mirror had been folded inside the nose cone of the rocket before the launch. After weeks of other important spacecraft deployments, the team started to unfold the hexagonal segments of the mirror, the largest ever launched into space. This was done at the end of last week and was then followed by the secondary mirror.
The honeycomb-shaped mirror measures 21 feet (6.5 meters) across, three times the size of Hubble’s mirror. It will be sensitive enough in order to see celestial objects undetectable by previous observatories, enabling us to peer into the depths of the universe with unprecedented accuracy. Its deployment also marks the end of a very important first phase after the Webb was launched on Christmas Day.
“NASA achieved another engineering milestone decades in the making. While the journey is not complete, I join the Webb team in breathing a little easier and imagining the future breakthroughs bound to inspire the world,” NASA Administrator Bill Nelson said in a statement. “The James Webb Space Telescope is an unprecedented mission,” he added.
The telescope is expected to arrive at its destination by January 23. Then it will use its engines to reach a spot about 1.5 million kilometers (930,000 miles) away from Earth, known as L2 — a so-called Lagrangian Point where gravity will keep the telescope stable. But there’s a lot more coming up. Team members will spend the next two weeks aligning all mirror segments to perform as one, NASA said in a press conference.
NASA chose L2 specifically due to its ideal conditions for Webb to work. Its great distance from the sun, combined with its recently deployed sunshield, will allow the telescope to do its infrared observations without any disturbance. If all goes well, and we hope it does, Webb will give us an inside look into the universe and its evolution.
Webb has a set of science instruments that will allow observations in mid-infrared, near-infrared and visible wavelengths – including a combination of fine guidance sensor and spectrograph, a near-infrared camera and spectrograph, and a mid-infrared instrument. It’s the world’s largest and most complex space science telescope.
This week, NASA will start with the basic aligning of the mirrors, a task that will take about three months in order to get them ready for the telescope’s first testing image. These will likely be blurry, NASA said, anticipating any questions, as Webb won’t be fully ready yet. More imaging and testing will be needed to get the configuration right
“The successful completion of all of the Webb Space Telescope’s deployments is historic,” Gregory L. Robinson, Webb program director at NASA, said in a statement. “This is the first time a NASA-led mission has ever attempted to complete a complex sequence to unfold an observatory in space – a remarkable feat for our team, NASA, and the world.”
It took a few more days than expected but the enormous 21-meter (70-foot) sunshield of the James Webb Space Telescope has now been deployed, an important milestone that brings the telescope closer and closer to becoming operational. NASA team members clapped and cheered as they followed the process, but there’s still a bit left to go before the telescope can commence operations.
The telescope, which cost $10 billion and was launched on Christmas Day, is the most powerful ever sent to space, with a mirror six times bigger than the one included in the Hubble. It has been carefully unfolding in zero gravity for days. While all the required setup steps are tricky, setting up the sunshield was considered the most difficult part.
It was a big moment for the engineering teams at NASA and the American aerospace manufacturer Northrop Grumman, the main contractor for the telescope. Years of testing on sub-scale and full-scale models paid off as controllers separated the five layers of the sunshield and tensioned them – all controlled remotely from Earth.
“This is the first time anyone has ever attempted to put a telescope this large into space,” Thomas Zurbuchen, associate administrator for NASA’s Science Mission Directorate, said in a statement. The success of its most challenging deployment – the sunshield – is an incredible testament to the human ingenuity and engineering skill.”
The very important sunshield
The sunshield will safeguard the telescope from the heat and the light of the Earth, Sun, and Moon. The five plastic layers are as thin as a human hair and are coated with reflective metal. Together, they reduce exposure from the Sun from 200 kilowatts to a fraction of a watt – crucial to keep the scientific instruments cold enough to work.
The team at NASA had delayed the sunshield deployment and tensioning to make sure Webb’s power systems were good to go. The task meant using 139 of the 178 release mechanisms included in the telescope, as well as eight deployment motors, 400 pulleys, and 90 cables. Any mistakes at this part could have doomed the telescope.
“Unfolding Webb’s sunshield in space is an incredible milestone, crucial to the success of the mission,” Gregory L. Robinson, Webb’s program director at NASA, said in a statement. “Thousands of parts had to work with precision for this marvel of engineering to fully unfurl. The team has accomplished an audacious feat with the complexity of this deployment.”
While it all went smoothly, several steps still remain for the telescope to become operational – including the deployment of the telescope’s main and secondary mirrors. This would start this weekend and last for 10 days. It’s the biggest mirror NASA has ever built, so big that engineers had to design the Webb as moving parts that can fold in the rocket.
The telescope is now on its way to its job site, a million miles from Earth, where it will sit in a solar orbit and be held stable by the gravitational pull of the Sun and the Earth. Once fully operational, the telescopes will look at all aspects of cosmic history. Thanks to its infrared observations, it can look deeper into the universe and even look back in time, enabling us an unprecedented view into the very depths of the universe.
Engineers at NASA decided to hold off tensioning the vast sunshield of the James Webb Space Telescope to allow more time to verify the overall performance of the observatory and ensure that everything is going according to plan. The key procedure was initially supposed to be carried out during the weekend and now it could begin as early as today, according to the latest statement by NASA.
The Webb telescope was launched on December 25th and is now under a deployment process due to take a month, necessary to get it ready to gather data. Most steps are controlled from the ground and while NASA has a schedule for the work, this is tentative and can be adjusted along the way by mission leaders – as it happened now. It’s one of the most striking scientific achievements in the past years, and engineers want to be sure everything runs smoothly.
“Nothing we can learn from simulations on the ground is as good as analyzing the observatory when it’s up and running,” Bill Ochs, Webb project manager, based at NASA’s Goddard center, said in a statement. “Now is the time to take the opportunity to learn everything we can about its baseline operations. Then we’ll take next steps.”
Work on the sunshield began last week, when the two pallets holding it were deployed and locked on either side of the telescope’s primary mirror. Protective covers were rolled off each pallet, exposing the sunshade membranes to space. On Friday, the two telescoping booms began extending, pulling out both sides of the shield and unfolding the membranes.
Now, with both booms already extended, the sunshield must be tensioned to produce a gap between each layer, generating space for excess heat to migrate. But as the boom extension took longer than expected, mission managers delayed tensioning first to Saturday and then to Sunday, making sure the motors were at the required temperature.
NASA doesn’t give live coverage of the Webb telescope deployment, with the last media briefing held on Christmas Day after the launch. But in its latest blog, the space agency said engineers wanted to better understand how the Webb is functioning in its new environment, ensuring the motors to be used for sunshield tensioning are at optimal temperatures.
Since its launch, Webb has already corrected its trajectory with two precision thruster firings, deployed its solar panel, unlimbered the antenna it will use to send back data to Earth and extended a flap to counteract the solar wind pressure. So far, so good. The telescope has also elevated its main mirror and science instruments to isolate them from the heat generated by on-board systems.
“We’ve spent 20 years on the ground with Webb, designing, developing, and testing,” Mike Menzel, Webb’s lead systems engineer, said in a statement. “We’ve had a week to see how the observatory actually behaves in space. It’s not uncommon to learn certain characteristics of your spacecraft once you’re in flight. That’s what we’re doing right now.”
The sunshield, made of five thin Kapton layers, is very important for the telescope’s goal of capturing light from the stars and galaxies that lighted up after the Big Bang of the cosmos 14 billion years ago. The telescope has to be refrigerated to within 50 degrees of absolute zero (400 degrees below zero Fahrenheit) in order to register that radiation. The first images from Webb should be available by summer 2022.
Gravitational waves are disturbances in space-time generated by some of the largest and most energetic events in the universe. They propagate as waves from a source at the speed of light.
In Einstein’s general theory of relativity, gravity is considered a curvature of spacetime — a curvature caused by the presence of mass. The larger and more compact the mass is, the greater the curvature. For physicists, gravitational waves are also the wave-like solution of Einstein’s equations and the only way through which some phenomena in the universe can be observed.
For instance, when the orbits of two massive bodies change over time, this seemingly results in a loss of energy. But energy can’t be lost, so it must go somewhere — and the only way to explain that loss is that the energy is used to produce waves in space-time, emitting gravitational radiation.
The theory lined up well, but there was a problem: for decades, researchers couldn’t truly detect these gravitational waves, and without validation, the theory couldn’t be confirmed. That all changed in 2015, with the first gravitational waves (GW150914) being directly observed by the two Laser Interferometer Gravitational Wave Observatory (LIGO) detectors. Three years later, the three main scientists behind the detection received the Nobel Prize for the discovery. But researchers may have discovered gravitational waves way earlier, in 1982.
In 1974, two astrophysicists, (Russell Alan Hulse and Joseph Hooton Taylor Jr) were carrying out a pulsar survey at the Arecibo Observatory, a radio telescope with a 305 meter (1,000 ft) dome. You may remember Arecibo as that big telescope that collapsed to rubble in late 2020 due to underfunding and neglect. Pulsars are a type of compact stars that emit radio or X-ray radiation — they’re a sort of cosmic lighthouse that spins, and whenever it emits a signal towards the Earth, we can detect.
There’s an important reason why Arecibo was so big. The goal of radio telescopes is to detect radio waves — waves for which the wavelength can measure even more than the Earth’s radius. The sources of radio waves outside the solar system are really weak, so we need very big dishes to detect those objects — and Arecibo successfully detected something.
The scientists detected a ‘weird’ pulsar, later named PSR B1913+16 or the “Hulse-Taylor binary”. Researchers noticed that the pulsation period of this pulsar is not stable — it changes and returns to the original state every 7.75 hours. The only explanation for that change was that the pulsar is in a binary system, the pulsar was completing an orbit every 7.75 hours. They knew that thanks to the Doppler effect.
When a light source is moving away from us, its frequency is shifted to the red side of the visible spectrum — and when it moves towards us it is shifted to blue. By measuring the pulsar period, Taylor and Hulse were able to plot a velocity curve to help analyze the orbit and try to figure out who was the pulsar’s companion.
In their analysis, they observed that system does not have a circular orbit but an ellipse. In the end, they concluded the pulsar lived in a binary system with another compact star, but they could yet not conclude if it was also pulsar or not.
By now, you’re probably wondering what this all has to do with gravitational waves. We’re almost there.
Eight years later, without stopping the observations, Taylor and Joel M. Weisberg realized the orbital velocity was increasing, meaning the stars were accelerating. They had also improved their knowledge of the system and figured that both stars have nearly the same mass of 1.4 solar masses and that their orbit is tight, around 4.5 times the Sun’s radius (or 9 times the distance from the Earth to the Moon). The pulsar’s companion is probably another pulsar, they concluded, but we just cannot get its radio signal because the beams it emits are never pointed towards Earth.
The binary was the perfect candidate to test the gravitational waves solution to Einstein’s equations, but because we couldn’t get direct information from the waves themselves, Taylor and Weisberg used theory to indirectly connect the observations from the pulse’s period. They noticed that the orbital period between the stars was decreasing with time, which means it was losing energy — presumably to gravitational waves.
While Arecibo was still working, the observations continued, and 30 years later, the same theory continued to fit the estimated loss of the orbital period, hinting more and more that the binary is emitting gravitational waves. The jaw-dropping conclusion of the study is the almost perfect agreement between the points (in red below) and the theory (blue line) almost as if there isn’t a minimal mistake in Einstein’s theory. Although they didn’t have any direct observation, astronomers had most likely detected gravitational waves indirectly.
The discovery of the binary pulsar resulted in a Nobel prize in 1993 for Taylor and Hulse, but not for the gravitational waves indirect detection. PSR1913+16 has always been the observation that paved the way for the gravitational waves interferometer, with the binary it was almost certain that the theory was correct, scientists just needed to be lucky enough to observe the phenomenon. It happened and in 2017, the Nobel prize in physics was awarded to LIGO researchers for the first solid detection.
The Arecibo radio telescope collapsed a year ago. The iconic telescope that made the first detection of binary pulsars, and many others, fell to rubble as it struggled to obtain funding in recent years. The data collected by the telescope is still used by scientists, the most recent was published exactly one year after its collapse, the research tries to understand the history of galaxies with their stellar mass.
Astronomers have discovered a one-kilometre wide asteroid orbiting the Sun at a distance of just 20 million km (12 million miles). Not only does this make the asteroid–currently designated 2021 PH27–the Sun’s closest neighbour, but it also means that as it completes an orbit in just 113 days, it is also the solar system’s fastest-orbiting asteroid. 2021 PH27 skirts so close to the Sun that its discoverers say its surface temperature is around 500 degrees C–hot enough to melt lead.
Scott S. Sheppard of the Carnegie Institution of Science first spotted asteroid 2021 PH27 in data collected by the Dark Energy Camera (DECam) mounted at the prime focus of the Victor M. Blanco 4m Telescope at Cerro Tololo Inter-American Observatory (CTIO), Chile. Brown University astronomers Ian Dell’antonio and Shenming Fu took images of the asteroid on 13th August 2021 at twilight–the optimum time for hunting asteroids that lurk close to the Sun. Just like the inner planets–Mercury and Venus–asteroids that exist within the Earth’s orbit become most visible at either sunrise or sunset.
The discovery was followed by measurements of the asteroid’s position conducted by David Tholen of the University of Hawai‘i. These measurements allowed astronomers to predict asteroid 2021 PH27’s future position, leading to follow-up observations on the 14th of August by DECam and the Magellan Telescopes at the Las Campanas Observatory in Chile.
These observations were then subsequently followed on August 15th by imaging made with the LasCumbres Observatory network of 1- to 2-meter telescopes located in Chile and South America by European Space Agency (ESA) researcher Marco Micheli.
The findings were so significant that many astronomers cancelled their scheduled projects to use telescope time with a variety of sophisticated instruments to further observe the asteroid. “Though telescope time for astronomers is very precious, the international nature and love of the unknown make astronomers very willing to override their own science and observations to follow up new, interesting discoveries like this,” explains Sheppard.
What makes the discovery of asteroid 2021 PH27 so special, and of great interest to astronomers, is the fact that it belongs to a population of solar system bodies that have been, thus far, notoriously difficult to spot.
Hunting For Inner Solar System Asteroids
Interior asteroids that exist close to the Sun tend to be difficult for astronomers to spot because of the glare from our central star. This difficulty is amplified by the fact that as they get close to the Sun these objects experience intense gravitational, tidal, and thermal forces that breaks them up into smaller–thus tougher to spot–fragments.
That means tracking an intact interior asteroid could have benefits for our understanding of these objects and the conditions they experience. In particular, if there are few asteroids experiencing a similar orbit to asteroid 2021 PH27 it may indicate to astronomers many of these objects were loose ‘rubble piles.’ This may, in turn, give us a good idea of the composition of asteroids on a collision course with Earth, and crucially, how we could go about deflecting them.
“The fraction of asteroids interior to Earth and Venus compared to the exterior will give us insights into the strength and make-up of these objects,” Sheppard continues. “Understanding the population of asteroids interior to Earth’s orbit is important to complete the census of asteroids near Earth, including some of the most likely Earth impactors that may approach Earth during daylight and that cannot easily be discovered in most surveys that are observing at night, away from the Sun.”
In addition to this, asteroid 2021 PH27’s orbit is so close to the Sun that our stars exerts considerable gravitational effects upon it, something that could make it a prime target for the study of Einstein’s geometric theory of gravity–better known as general relativity.
This close proximity to the Sun may actually be a recent development for asteroid 2021 PH27.
Asterod 2021 PH27 is on the Move
Planets and asteroids don’t move around their stars in perfectly circular orbits, but in ellipses–flattened out circles. The ‘flatter’ the circle the greater we say its eccentricity is. The widest point of the ellipse is the semi-major axis and for an orbit, this represents the point at which a body is farthest from its parent star.
Asteroid 2021 PH27 has a semi-major axis of 70 million kilometres (43 million miles or 0.46 au) which gives it a 113-day orbit crossing the orbits of both Venus and Mercury. But it may not have always existed so close to the Sun.
Astronomers believe that the asteroid may have started life in the main asteroid belt between Mars and Jupiter, with the gravitational influence of the inner planets drawing it closer to the Sun. This would make it similar to the Near-Earth Object (NEO) Apophis, which has only recently been ruled out as a potential Earth impactor, which was also dragged closer to the Sun by gravitational interactions.
There is also some evidence arising from 2021 PH27’s high orbital inclination of 32 degrees that the asteroid may have a slightly more exotic origin, however. This could imply that the asteroid is actually an extinct comet that comes from the outer edge of the solar system pulled into a close orbit as it passed an inner-terrestrial–rocky–planet. Astronomers will be looking to future observations to determine which of these origins is correct, but unfortunately, this will have to wait. 2021 PH27 is about to enter solar conjunction which means that from our vantage point on Earth it is about to move behind the Sun. That means the asteroid will only become available for further observations in 2022.
These follow-up observations will allow astronomers to better determine its orbit. And with this better determination will come a new official name that is hopefully a bit less of a mouthful than 2021 PH27. But what is certain is that this asteroid is not set to become any less interesting.
The surfaces of neutron stars may feature mountains, albeit ones that are no more than millimetres tall, new research has revealed. The minuscule scale of neutron star mountains is a result of the intense gravity produced by these stellar remnants that are the second densest objects in the Universe after black holes.
Because neutron stars have the mass equivalent to a star like the Sun compressed into a diameter that is about the size of a city on Earth–about 10km– they have a gravitational pull at their surface that is as much as 40,000 billion times stronger than Earth’s.
This presses features on that surface flat, making for almost perfect spheres. Yet the new research, presented at the National Astronomy Meeting 2021 shows that these stellar remnants do feature some tiny topological deformations, analogous to mountains on a planet’s surface.
The finding was a result of complex computer modelling by a team of researchers led by the University of Southhampton’s Fabian Gittins. The Ph.D. student’s team simulated a realistic neutron star and then calculated the forces acting upon it. What the research really shows is how well neutron stars can support deviations from a perfect sphere without its crust being strained beyond breaking point.
This revealed how mountains could be created on such dense stellar remnants and demonstrated that such formations would be no taller than a fraction of a millimetre.
“For the past two decades, there has been much interest in understanding how large these mountains can be before the crust of the neutron star breaks, and the mountain can no longer be supported,” says Gittins. These results show how neutron stars truly are remarkably spherical objects. “Additionally, they suggest that observing gravitational waves from rotating neutron stars maybe even more challenging than previously thought”.”
Mountain formation has been formulated for neutron stars before, but these new findings suggest such features would be hundreds of times smaller than the mountains of a few centimetres previously predicted. This is because those older models took the crusts of neutron stars to the edge of breaking point at every single point; something the up-to-date research suggests is less than realistic.
Neutron stars form when massive stars run out of fuel to power nuclear fusion. This means that the toward force balancing against gravity’s inward pull is cancelled and leads to the gravitational collapse of the star. During the course of this collapse, the massive star ejects its outer material in supernova explosions and leaving behind a core of ultradense material. This stellar remnant is only protected from further collapse–and in turn, becoming a black hole–by the quantum mechanical properties of the neutron-rich material that composes it.
The finding may have implications that go beyond the modelling of neutron stars. Tiny deformations on the surface of rapidly spinning neutron stars called pulsars could launch gravitational waves–the tiny ripples in spacetime predicted by general relativity and detected here on Earth by the LIGO/Virgo collaboration.
Unfortunately, as precise and sensitive as the LIGO laser interferometer is, it is still not powerful enough to detect gravitational waves launched by these ant-hill like mountains. It is possible that future upgrades to these Earth-based detectors and advancements such as the space-based gravitational wave detector LISA could make observing the effect of these tiny bumps possible.
Six galaxies detected by Hubble and Spitzer come from a time astronomers call the Cosmic Dawn — a period in the history of our universe just 250-350 million years after the Big Bang (the age of the universe is currently estimated at 13.8 billion years), when the first stars had just started shining.
After the Big Bang, the universe was a bit of a hot mess. It was hot, dense, and virtually opaque. It only became transparent during a period called Recombination, in which a soup of protons and electrons combined to form the first true hydrogen atoms. Prior to the Recombination, the light was not able to travel freely travel through the universe as it was constantly scattered off the free electrons and protons. But as the atoms started combining and there were fewer free particles, this forged a free path for light to travel the universe.
It is in this period that the universe became transparent — and it is also in this period that the six galaxies were formed. It took light from these galaxies most of the universe’s current lifetime to get to us, and looking at them is basically like looking at the Cosmic Dawn. For Professor Richard Ellis from University College London, UK, observations like this are the crowning of decades of work.
In a study published in Monthly Notices of the Royal Astronomical Society, Ellis and colleagues from the UK, Germany, and US, estimated the time at which the Cosmic Dawn began by using six galaxies which they estimate to have formed between 250 to 350 million years after the Big Bang.
In order to estimate the galaxies’ age, they must first consider a particular value of the universe’s rate of expansion (over which there is still some debate). The reason for that is because they are computing the lookback time — the time light from the ancient galaxies traveled to reach us.
As the universe expands, light coming from stars and galaxies has its wavelength increased — something called the redshift effect. By looking at how much the wavelength has increased, researchers can estimate how much light has traveled — and consequently, how old the light-producing object is.
The recent results were based on data from the Hubble and Spitzer space telescopes, both famous for being capable of observing some of the oldest objects in the universe. To estimate the redshift, the team required the Chilean Atacama Large Millimetre Array (ALMA), the European Very Large Telescope, the twin Keck telescopes in Hawaii, and Gemini-South telescope.
The age of the sample is only computed by combining data from all those different telescopes. However, astronomers and cosmologists have great expectations of the Hubble/Spitzer successor, the James Webb Space Telescope (JWST). The most ambitious, the biggest, and the most sensitive telescope NASA created will be able to observe those Cosmic Dawn galaxies directly. JWST is also the hope of a larger sample of galaxies, providing a better representation of the Cosmic Dawn.
One of the major problems which has hindered our understanding of planet formation has been the lack of direct measurements of the mass of planet-forming protoplanetary discs. Now, by successfully measuring the mass of a unique protoplanetary disc for the first time, astronomers have confirmed that gravitational instabilities play a key role in the formation of planets.
The team of astronomers, led by Teresa Paneque-Carreño, a PhD student at the University of Leiden and the European Southern Observatory (ESO), used gas velocity data collected using the Atacama Large Millimeter/submillimeter Array (ALMA) to make observations of the young star Elias 2-27 which is surrounded by a disc of gas and dust with some extraordinary features.
The star which is located just under 400 light-years from Earth in the constellation Ophiuchus has been a popular target for investigation by astronomers for at least five decades which paid off in 2016 with the discovery that the young star is surrounded by a disc of gas and dust. This marks the first time, however, that such a mass measurement has been made and gravitational instabilities have been confirmed.
“How exactly planets form is one of the main questions in our field. However, there are some key mechanisms that we believe can accelerate the process of planet formation,” explains Paneque-Carreño. “We found direct evidence for gravitational instabilities in Elias 2-27, which is very exciting because this is the first time that we can show kinematic and multi-wavelength proof of a system being gravitationally unstable.
“Elias 2-27 is the first system that checks all of the boxes.”
Teresa Paneque-Carreño, University of Leiden
Paneque-Carreño is the first author of one of two papers detailing the team’s findings–which give astronomers the key to unlocking the mystery of planet formation– published in the latest edition of The Astrophysical Journal.
What makes Elias 2-27 the Ideal System for Cracking the Planet Formation Mystery?
Researchers have known for some time that protoplanetary discs of gas and dust surrounding young stars are locations of planet formation and we have certainly no shortage of studies of such structures. But, despite having this knowledge and a wealth of observational data, the exact process that leads to the birth of a planet has remained a puzzle.
Fortunately, telltale evidence of gravitational instabilities around Elias 2-27 made it the ideal star for astronomers in order to conduct a thorough investigation of planet formation.
“We discovered in 2016 that the Elias 2-27 disk had a different structure from other already studied systems, something not observed in a protoplanetary disk before: two large-scale spiral arms,” remarks principal investigator Laura Pérez, Assistant Professor at the Universidad de Chile. “Gravitational instabilities were a strong possibility, but the origin of these structures remained a mystery and we needed further observations.”
It was Pérez who suggested that ALMA–a series of 66 radio telescopes located in the Atacama Desert of northern Chile–should be trained on the spiral of gas and dust surrounding this young star.
It was this further study that revealed, not only does Elias 2-27 possess a protoplanetary disc with signs of gravitational instabilities within it, it also has something unique for such a structure: spiral arms.
Elias 2-27: A Unique and Chaotic Young Star System
The presence of spiral arms in the protoplanetary disc is believed to be the result of perturbations caused by density waves throughout the gas and dust that comprise it.
It is the first star-forming disc discovered with such features. But, to Paneque-Carreño it signals the presence of something else within the disc, chaos. This chaotic nature also gives rise to another characteristic never seen in a disc such as this.
“There may still be new material from the surrounding molecular cloud falling onto the disc, which makes everything more chaotic,” says the graduate of the Universidad de Chile. “The Elias 2-27 star system is highly asymmetric in the gas structure. This was completely unexpected, and it is the first time we’ve observed such vertical asymmetry in a protoplanetary disc.”
It is the double-punch of this vertical asymmetry and large-scale perturbations giving rise to a spiral structure that Cassandra Hall, Assistant Professor of Computational Astrophysics, University of Georgia, believes has major implications for our theories of planet formation.
“This could be a ‘smoking gun’ of gravitational instability, which may accelerate some of the earliest stages of planet formation,” says Hall, a co-author of one of the papers detailing these findings. “We first predicted this signature in 2020, and from a computational astrophysics point of view, it’s exciting to be right.”
This research has cracked the problem of measuring the mass of a protoplanetary disc, thus removing a significant barrier in our understanding of planet formation. This was possible in large part due to the high sensitivity of ALMA’s observing bands, particularly band 6 which covers light with a wavelength of 1.1 to 1.4 nanometres in combination with bands 3 and 7–which cover 2.6 – 3.6 nm and 0.8 -1.1 nm, respectively.
“Previous measurements of protoplanetary disc mass were indirect and based only on dust or rare isotopologues. With this new study, we are now sensitive to the entire mass of the disc,” says the second paper’s lead author Benedetta Veronesi, a postdoctoral researcher at École normale supérieure de Lyon. “This finding lays the foundation for the development of a method to measure disc mass that will allow us to break down one of the biggest and most pressing barriers in the field of planet formation. “
“Knowing the amount of mass present in planet-forming discs allows us to determine the amount of material available for the formation of planetary systems, and to better understand the process by which they form.”
Benedetta Veronesi, École normale supérieure de Lyon
More Planet Formation Mysteries to Solve
Even though this research has answered some of the questions surrounding the process of planet formation, like the best scientific discoveries, it has also given rise to new questions.
“While gravitational instabilities can now be confirmed to explain the spiral structures in the dust continuum surrounding the star, there is also an inner gap, or missing material in the disk, for which we do not have a clear explanation,” explains Paneque-Carreño.
Many of these questions are difficult to answer because of the vast difference between the timescales on which we live and those taken by the processes that birth planets.
“Studying how planets form is difficult because it takes millions of years to form planets. This is a very short time-scale for stars, which live thousands of millions of years, but a very long process for us,” said Paneque-Carreño. “What we can do is observe young stars, with disks of gas and dust around them, and try to explain why these disks of material look the way they do. It’s like looking at a crime scene and trying to guess what happened. “
Fortunately, researchers like Paneque-Carreño, Cassandra Hall, and Benedetta Veronesi are prepared to tackle this monumental challenge and solve planet formation’s remaining mysteries.
“Our observational analysis paired with future in-depth analysis of Elias 2-27 will allow us to characterize exactly how gravitational instabilities act in planet-forming discs and gain more insight into how planets are formed,” concludes Paneque-Carreño.
In late 2019 and early 2020 Betelgeuse, a red supergiant in the constellation of Orion, made headlines when it underwent a period of extreme dimming. This dip in brightness for the star, which is usually around the tenth brightest in the night sky over Earth, was so extreme it could even be seen with the naked eye.
Some scientists even speculated that the orange-hued supergiant may be about to go supernova, an event which would have been visible in daylight over Earth for months thanks to its power and relative proximity–700 light-years from Earth. Yet, that supernova didn’t happen and Betelgeuse returned to its normal brightness.
This left the ‘great dimming’ of Betelgeuse–something never seen in 150 years of studying the star–an open mystery for astronomers to investigate.
Now, a team of astronomers led by Miguel Montargès, Observatoire de Paris, France, and KU Leuven, Belgium, and including Emily Cannon, KU Leuven, have found the cause of this dimming, thus finally solving this cosmic mystery. The researchers have discovered that the darkening of Betelgeuse was caused by a cloud of dust partially concealing the red supergiant.
“Our observations show that the Southern part of the star was hidden and that the whole disk of the star was fainter. The modelling is compatible with both a cool spot of the photosphere and a dusty clump in front of the star,” Montargès tells ZME Science. “Since both signatures have been detected by other observers, we conclude that the Great Dimming was caused by a cool patch of material that, due to its lower temperature, caused dust to form in gas cloud ejected by the star months to years before.”
The ‘great dimming’ of this massive star lasted a few months presented a unique opportunity for researchers to study the dimming of stars in real-time.
“The dimming of Betelgeuse was interesting to professional and amateur astronomers because not only was the appearance of the star changing in real time we could also see this change with the naked eye. Being able to resolve the surface of a star during an event like this is unprecedented.”
Emily Cannon, KU Leuven
The team’s research is published in the latest edition of the journal Nature.
A Unique Opportunity to Capture a Dimming Star
Montargès and his team first trained the Very Large Telescope (VLT)–an ESO operated telescope based in the Atacama Desert, Chile–on Betelgeuse when it began to dim in late 2019. The astronomers took advantage of the Spectro-Polarimetric High-contrast Exoplanet REsearch (SPHERE) instrument at the VLT as well as data from the telescope’s GRAVITY instrument. This allowed them to create stunning images tracking the great dimming event allowing them to distinguish it from regular dips in brightness demonstrated by the supergiant stars.
Betelgeuse has been seen to decrease in brightness before as a result of its convection cycle, which causes material to rise and fall throughout the star’s layers based on its temperature. This convection cycle results in a semi-regular dimming cycle that lasts around 400 days.
When the ‘great dimming’ was first observed in October 2019 astronomers had assumed this was due to its natural dimming cycle. That assumption was dismissed by December that same year when the star became the darkest that it had been in a century. The star had returned to its normal brightness by April 2020.
“No other red supergiant star has been seen dimming that way, particularly to the naked eye. Even Betelgeuse that has been closely monitored for 150 years has not shown such behaviour.”
Miguel Montargès, Observatoire de Paris, France
Not only does this finding solve the mystery of this star’s dimming, but it also provides evidence of the cooling of a star causing the creation of stardust which goes on to obscure the star.
Even though Betelgeuse is much younger than the Sun–10 million years old compared to our star’s age of 4.6 billion years–it is much closer to the supernova explosion that will signal the end of its lifecycle. Astronomers had first assumed that dimming was a sign that the red supergiant was exhibiting its death throes ahead of schedule.
Thanks to the work of Montargès and his team, we now know this isn’t the case. The dimming is the result of a veil of stardust obscuring the star’s southern region.
“We have observed dust around red supergiant stars in the past,” Cannon explains. “However, this is the first time we have witnessed the formation of dust in real-time in the line of sight of a red supergiant star,”
This stardust will go on to form the building blocks of the next generation of stars and planets, and the observations made by Montargès, Cannon and the team represent the first time we have seen an ancient supergiant star ‘burping’ this precious material into the cosmos.
The Giant that Burped Stardust
The surface of Betelgeuse–which with its diameter of around 100 times that of the Sun would consume the orbits of the inner planets including Earth were it to sit in our solar system–is subject to regular changes as bubbles of gas move around it, change in size, and swell beneath it. Montargès, Cannon and their colleagues believe that sometime before the great dimming began the red supergiant ‘burped’ out a large bubble of gas.
This bubble moved away from the star leaving a cool patch on its surface. It was within this cool patch that material was able to solidify, creating a cloud of solid stardust. The team’s observations show for the first time that stardust can rapidly form on the surface of a star.
“We have directly witnessed the formation of so-called stardust,” says Montargès. “The dust expelled from cool evolved stars, such as the ejection we’ve just witnessed, could go on to become the building blocks of terrestrial planets and life.”
With regards to the future, the researchers point to the Extremely Large Telescope (ELT), currently under construction in the Atacama Desert as the ideal instrument to conduct further observations of Betelgeuse. “With the ability to reach unparalleled spatial resolutions, the ELT will enable us to directly image Betelgeuse in remarkable detail,” says Cannon. “It will also significantly expand the sample of red supergiants for which we can resolve the surface through direct imaging, further helping us to unravel the mysteries behind the winds of these massive stars.”
For Montargès solving this mystery and observing a phenomenon for the first time, solidifies a lifetime of fascination with Betelgeuse and points towards a deeper understanding of the stardust that is the building blocks of stars, planets, and us. “We have seen the production of star dust, materials we are ourselves made of. We have even seen a star temporarily change its behavior on a human time scale.”
Astronomers have spotted a rare giant ‘blinking’ star towards the centre of the Milky Way. The team believes the serendipitous discovery, which came after 17 years of observation, represents another example of a rare class of ‘blinking giant’ stars that represents an eclipsing binary system.
The giant star with a mass around 100 times that of the Sun–designated VW-WIT-08–was spotted by the international team of researchers as it decreased in brightness by a factor of 30. A dimming extreme enough to result in the star almost disappearing entirely from the sky.
Changes in brightness such as this are usually associated with stars that pulsate or stars that exist in a binary system and are eclipsed by their companion star.
This giant star, which is located around 25,000 light-years away from Earth, dimmed for a period of several months in 2013 and then lightened again. A characteristic not commonly associated with the dimming mechanisms listed above.
The team of astronomers that have been investigating VW-WIT-08 believe that the dimming it demonstrated eight years ago and has not repeated since is the result of an as-of-yet unseen object orbital companion eclipsing the giant star.
They add that this eclipsing object could be another star or a planet, but one thing that is fairly certain is that it is surrounded by some form of an opaque disc which is responsible for causing the star’s extreme dimming.
“It’s amazing that we just observed a dark, large and elongated object pass between us and the distant star, and we can only speculate what its origin is,” says Sergey Koposov from the University of Edinburgh.
Alongside Leigh Smith from the Institute of Astronomy, the University of Cambridge, and Philip Lucas from the University of Hertfordshire, Koposov is one of the authors of a paper detailing the discovery published in the journal Monthly Notices of the Royal Astronomical Society.
VW-WIT-08 isn’t the only example of a star dimming in this unusual fashion, but arguably it is the most extreme example discovered thus far.
What’s Going On with Giant Blinking Stars?
Another example of this form of an eclipsing binary system is Epsilon Aurigae, first discovered in 1821 by German astronomer Johann Heinrich Fritsch. The visible component of this binary system is the supergiant star Almaaz–an Arabic name meaning the he-goat–which dims by around 50% every 27 years.
Though this dimming is less pronounced than that of VW-WIT-08, it lasts for a prolonged period of time; between 640 and 730 days–around two years. This means the dimming component of this binary system must be something truely immense, probably another star surrounded by a thick ring of obscuring dust, angled edge-on from our perspective.
Whilst this two-year eclipse which last occurred between 2009 and 2011 may seem extreme, it’s topped by the eclipse seen in another similar system discovered more recently–TYC 2505-672-1 found around 10,000 light-years from Earth.
This system currently holds the record for the longest known eclipse. Every 69 years the massive star component of this system is dimmed by a magnitude of 4.5 for a period of around 3 and a half years.
Thanks to the team that found VW-WIT-08 the catalogue of these eclipsing binary systems looks set to expand as the astronomers have currently found two more giant blinking stars ripe for further investigation.
“Occasionally we find variable stars that don’t fit into any established category, which we call ‘what-is-this?’, or ‘WIT’ objects,” remarks Lucas. “We really don’t know how these blinking giants came to be.”
What Does the Future Hold for Giant Blinking Stars?
The team made the discovery of VVV-WIT-08 using data collected by VISTA Variables , part of the Via Lactea (VVV Survey) which ran from 2010 to 2016. The survey’s main mission was the observation of the Milky Way’s central bulge and southern disc in near-infrared. The project utilised the capabilities of the VISTA telescope located at the Parnal Observatory, Chile.
Lucas adds: “It’s exciting to see such discoveries from VVV after so many years planning and gathering the data.”
The dimming of VVV-WIT-08 was also captured by the Gravitational Lensing Experiment (OGLE) operated by researchers at the University of Warsaw. Our galaxy’s central bulge was also a primary target for OGLE which makes its observations in light closer to the visible range of the electromagnetic spectrum.
The main advantage of OGLE is the fact that it makes frequent observations, something that was vital for building a model of VVV-WIT-08. This combination of observations also showed the astronomers that the giant star dims in both the visible spectrum and the infrared spectrum.
The team’s findings show that there are undoubtedly more eclipsing binary systems in the Milky Way left to be discovered. But this may not be the most difficult part of the process of investigating these systems.
“There are certainly more to be found, but the challenge now is in figuring out what the hidden companions are, and how they came to be surrounded by discs, despite orbiting so far from the giant star,” Smith concludes. “In doing so, we might learn something new about how these kinds of systems evolve.”
Astronomers have completed the first in-depth census of molecular clouds in the nearby Universe. The study has revealed that these star-forming regions not only look different but also behave differently. This finding runs in opposition to previous scientific consensus, which considered these clouds of dust and gas to be fairly uniform.
The project–Physics at High Angular Resolution in Nearby GalaxieS (PHANGS)–consisted of a systematic survey of 100,000 molecular clouds in 90 galaxies in the local Universe. The primary aim of the PHANGS was to get an idea of how these star-forming regions are influenced by their parent galaxies.
The census was conducted with the use of the Atacama Large Millimeter/ submillimeter Array (ALMA) located on the Chajnantor plateau, in the Atacama Desert of northern Chile. Whilst not marking the first time stellar nurseries have been studied with ALMA, this is the first census of its kind to observe globular clusters across more than either one galaxy or a small region of a single galaxy.
“We have carried out the first real ‘census’ of these stellar nurseries, and it provided us with details about their masses, locations, and other properties,” Adam Leroy, Associate Professor of Astronomy at Ohio State University (OSU) tells ZME Science. “Some people thought that all stellar nurseries across every galaxy look more or less the same, and it took having a really big, sensitive, and high-resolution survey of many galaxies with a telescope such as ALMA to see that this is not the case. This survey allows us to see how the stellar nurseries change across different galaxies. “
As a result, this is the first time that astronomers have been granted a look at the ‘big picture’ when it comes to these star-forming regions. Erik Rosolowsky, Associate Professor of Physics at the University of Alberta, and a co-author of the research points out that what ALMA has allowed the team of astronomers to create is essentially a new form of ‘cosmic cartography’ consisting of 90 maps of unparalleled detail detailing the regions of space where the next generation of stars will be born.
“By doing this we will combine what we are learning from ALMA about the clouds that form stars with pictures of newly formed stars from these other telescopes. This promises to give us the best view ever of the full life cycle of these stellar nurseries, and our most complete picture ever of the full cycle of star birth and death.”
“Our survey is the first one to capture the demographics of these stellar nurseries across a large number of the galaxies near the Milky Way,” adds Leroy, the lead author of a paper presenting the PHANGS ALMA survey. “We used these measurements to measure the characteristics of these nurseries, their lifetimes, and the ability of these objects to form new stars.”
How Galactic Neighborhoods Influence Star-Forming Clouds
The variety displayed by the molecular clouds surveyed in the PHANGS project was visible due to ALMA’s ability to take millimeter-wave images with the same sharpness and quality as images taken in the visible spectrum.
“While optical pictures show us light from stars, these ground-breaking new images show us the molecular clouds that form those stars,” says Leroy. “That helped us to see that stellar nurseries actually change from place to place.”
The team compared the changes displayed by molecular clouds from galaxy to galaxy to changes in houses, neighbourhoods and cities from region to region here on Earth.
“How stellar nurseries relate to their parent galaxies has been a big question for a long time. We’re able to answer this because our survey expands the amount of data on stellar nurseries by a factor of almost 100,” says Leroy. “Before this, it was very common to study a few hundred nurseries in one galaxy. So it was kind of like trying to learn about houses in general by looking only at neighbourhoods in Columbus, Ohio.
“You will learn some things about houses, but you miss the big picture and a lot of the variation, complexity, and commonality With this survey we looked at houses in many cities across many countries.”
Adam Leroy, Ohio State University
Leroy continues by explaining that stellar nurseries ‘know’ about their neighbourhood, meaning that molecular clouds are different depending on what galaxy they live in or where in that galaxy they are located. “So the stellar nurseries that we see in the Milky Way won’t be the same as those in a different galaxy, and the stellar nurseries in the outer part of a galaxy–where we live–aren’t the same as those near the galaxy centre.”
The team found clouds in the dense central regions of galaxies tend to be more massive, denser, and more turbulent than those located on the outskirts of a galaxy. In addition to this, the census revealed the lifecycle of clouds also depends on their environment. Annie Hughes, an astronomer at L’Institut de Recherche en Astrophysique et Planétologie (IRAP) explains that this means that both the rate at which a cloud forms stars and the processes that ultimately destroy clouds both seem to depend on where the cloud lives.
How Differences in Globular Clusters Influence the Birth of Stars
Because all stars are formed in molecular clouds, understanding the differences in these clouds of gas and dust and how they are caused by the conditions in which they exist is key to better understanding the processes that are driving the birth of stars like our own Sun.
These molecular clouds are so vast that they can birth anywhere from thousands to hundreds of thousands of stars before being exhausted of raw materials. These new observations have shown astronomers that each cosmic neighbourhood can have an effect on where stars are born and how many stars are spawned.
“Every star in the sky, in fact, every star in every galaxy, including our Sun, was born in one of these stellar nurseries. These are really the engines that build galaxies and make planets, and they’re just an essential part of the story of how we got here.”
Adam Leroy, Ohio State University
The next step for the astronomers will be to combine the data provided by ALMA with surveys conducted by other telescopes including the Hubble space telescope, and the Very Large Telescope (VLT) also located in the Atacama desert, Chile. Leroy hopes that this along with observations made with the James Webb Space Telescope (JWST), will help astronomers answer the question of how the diversity of molecular structures affects the stars which form within them. He explains: “By doing this we will combine what we are learning from ALMA about the clouds that form stars with pictures of newly formed stars from these other telescopes.
This promises to give us the best view ever of the full life cycle of these stellar nurseries, and our most complete picture ever of the full cycle of star birth and death.”
Adam Leroy, Ohio State University
Leroy concludes by pointing out why the study of these star-forming regions is so important. “This is the first time we have gotten a clear view of the population of these stellar nurseries across the whole nearby universe,” the researcher says. “It’s a big step towards understanding where we come from.”
The Dark Energy Survey (DES) is an ambitious cosmological project that aims to map hundreds of millions of galaxies. In the process, the project will detail hundreds of millions of galaxies, observe thousands of supernovae, map the cosmic web that links galaxies, all with the aim of investigating the mysterious force that is causing the Universe to expand at an accelerating rate.
Using the 570-megapixel Dark Energy Camera on the National Science Foundation’s Víctor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory (CTIO), Chile, the DES has observed a map of galaxy distribution and morphology that stretches 7 billion light-years and captures 1/8 of the sky over Earth.
Now new results from the DES which collects the work of an international team of over 400 scientists from over 25 institutions from countries including the US, UK, France, Spain, Brazil, and Australia, are in. The findings are detailed in a ground-breaking series of 29 papers and comprises of data collected during the DES’ first three years of operation providing the most detailed description of the Universe’s composition and expansion to date.
The survey was conducted between 2013 to 2019 cataloging hundreds of millions of objects, with the three years of data covered in these papers alone containing observations of at least 226 million galaxies observed over 345 nights.
The fact that some of these galaxies are close to the Milky Way and others are much more distant–up to 7 billion light-years away– gives researchers an excellent picture of the evolution of the Universe over around half of its lifetime.
The results seem to confirm the standard model of cosmology, currently the best-evidenced theory of the Universe’s composition and evolution which suggests the Universe was created in a ‘Big Bang’ event and has a composition of 5% ordinary or baryonic matter, 27% dark matter, and 68% dark energy.
The snapshot of the Universe provided by the DES does seem to show that the Universe is less ‘clumpy’ than current cosmological models suggest, however.
Illuminating the Dark Universe
The fact that the ‘Dark Universe’ consists of 95% of the matter and energy in the known cosmos means that there are huge gaps in our understanding of the evolution of the Universe, its past, present, and its future.
These gaps include the nature of dark matter, whose gravitational influence holds galaxies together, and dark energy, the force that is expanding space between the galaxies driving them apart at an accelerating rate.
These effects seem to be in opposition, with one holding matter together and the other working upon space itself to drive matter apart. And it is this cosmic struggle that shapes the Universe which the DES aimed to investigate.
There are two key phenomena which the survey used to do this. Studying ‘the cosmic web’ that links galaxies together in clusters and loose associations gives hints at the distribution and influence of dark matter.
The second phenomenon used by the DES is the bending of light as it travels past curvatures in spacetime created by objects of tremendous mass like galaxies. This effect predicted by Einstein’s theory of gravity–general relativity–is known as ‘gravitational lensing.’
The DES relied on a form of this effect called ‘weak gravitational lensing’ to assess how dark matter is distributed across the Universe, thus inferring its ‘clumpiness.’
The data collected by the DES was cross-referenced against measurements carried out by the European Space Agency (ESA) operated mission, the Planck observatory. The orbiting observatory, which operated between 2009 and 2013 and studied the cosmic background radiation (CMB)–an imprint leftover from an event shortly after the Big Bang in which electrons and protons connected thus allowing photons to travel freely for the first time.
Observing the CMB reveals conditions that were ‘frozen in’ to it at the time of this event known as the last scattering and thus gives a detailed picture of the Universe when it was just 400 thousand years old for the DES team to draw from.
Setting the Scene for Future Surveys
The DES intensely studied ten regions labeled as ‘deep fields’ which were repeatedly imaged during the course of the survey. These images were stacked which allowed astronomers to observe distant galaxies.
In addition to allowing researchers to see further into the Universe and thus further back in time, information regarding redshift– an increase in wavelength caused by objects receding which can arise as a result of the Universe’s expansion–taken from these deep fields was used to calibrate the rest of the survey. This constituted a major step forward for cosmic surveys providing the researchers with a picture of the Universe painted with stunning precision.
Whilst the DES was concluded in 2019, the sheer wealth of data collected by the survey requires a huge amount of computing power and time to assess. This is why we are only seeing the first three years of observations reported and likely means that the DES still has much more to deliver.
This will ultimately set the scene for the Legacy Survey of Space and Time (LSST) which will be conducted at the Vera C Rubin observatory–currently under construction on the El Penon peak of Cerro Pachon in northern Chile.
Whereas the DES surveyed an inarguably impressive 1/8 of the sky over the earth, the wide-field camera that will conduct the LSST will capture the entire sky over the Southern hemisphere, meaning it will view half of the entire sky over our planet.
A major part of the LSST’s mission will be the investigation of dark matter and dark energy, meaning that when the data from the DES is finally exhausted and its secrets are revealed, a worthy successor will be waiting in the wings to assume its mission of discovery.
Using data collected by the Very Large Telescope (VLT) a team of astronomers has discovered iron and nickel in the atmosphere of around 20 different solar system comets–including some located far away from the Sun.
These findings will come as a surprise to astronomers because even though such heavy metals have been known to exist in solid form within comet interiors before, the vapour of such elements has only previously been associated with cometary atmospheres in hot environments.
This is the first time such vapour has been seen in the cooler atmospheres of comets that exist far from a star and could indicate some previously unknown mechanism or material on the surface of comets.
“It was a big surprise to detect iron and nickel atoms in the atmosphere of all the comets we have observed in the last two decades, about 20 of them, and even in ones far from the Sun in the cold space environment,” says Jean Manfroid, of the University of Liège, Belgium.
This wasn’t the only surprise the team found, however. The Belgian astronomers–who have been studying comets with the VLT for 20 years–observed nickel and iron in the atmosphere of the comet in equal amounts.
Generally, iron is about ten times more abundant in the solar system than nickel, and comets are believed to be material left over from the formation of planetary bodies within the solar system. That means it’s something of a mystery why the comets the team observed should have such a relatively large abundance of nickel.
“Comets formed around 4.6 billion years ago, in the very young Solar System, and haven’t changed since that time. In that sense, they’re like fossils for astronomers,” Emmanuel Jehin, also from the University of Liège. “This discovery went under the radar for many years.”
Manfroid and Jehin are two of the authors of a paper published in the latest edition of the journal Nature documenting the team’s findings. And that isn’t the only research revealing metal in the atmosphere of such a body published in Nature this month.
The discovery is accompanied by the revelation that a separate team of researchers, this time located in Poland, has also found traces of nickel vapour in the atmosphere around the interstellar visitor 2l/Borisov.
This comet may sound familiar as it made headlines in 2019 when it became only the second object found within the solar system which originated from outside our planetary system.
A paper detailing this second finding is also published in this month’s Nature.
Heavy Metal Rocks
Astronomers have known for some time that a variety of metals exist within the icy and rocky interiors of comets. There have even been suggestions that spent comets could be mined for precious or useful metals like gold, silver, platinum and iron.
These solid metals within comets were not expected to be found as gases in the body’s atmosphere, though, unless that body is passing within close vicinity to a star.
It is the heat from these close brushes with stars like the Sun that causes solid metals within comets to ‘sublimate’–the process by which solid material changes directly into a gaseous state.
That means that distant comets in the cold environment of space away from the heat of the Sun shouldn’t have heavy metal atmospheres.
Yet, despite this, researchers have now found nickel and iron vapour in the atmospheres of comets up to 480 million kilometres from the Sun. A distance that is three astronomical units, or three times the distance between the Sun and the Earth.
In order to make this discovery, the team employed the technique of spectroscopy which reveals the signatures of specific chemical elements and the Ultraviolet and Visual Echelle Spectrograph (UVES) instrument on the VLT to assess the chemical composition of comets’ atmospheres.
The spectral lines of nickel and iron found by the team in comets’ atmospheres were extremely faint, which leads them to believe that the reason such elements have been missed in past is due to their tiny abundance. The team says that for every 100kg of water in the atmosphere of the comets they studied there is just one gram of iron and nickel respectively.
The Belgian astronomers believe that the equal amounts of iron and nickel together with the sublimation at low temperatures means there is something undiscovered at the surface of the comets they studied.
“Usually there is 10 times more iron than nickel, and in those comet atmospheres we found about the same quantity for both elements,” explains Damien Hutsemékers, also a member of the Belgian team from the University of Liège.”We came to the conclusion they might come from a special kind of material on the surface of the comet nucleus, sublimating at a rather low temperature and releasing iron and nickel in about the same proportions.”
The team intends to attempt to use new telescope technology such as the Mid-infrared ELT Imager and Spectrograph (METIS) on ESO’s upcoming Extremely Large Telescope (ELT)–currently under construction in the Atacama Desert region of Northern Chile– to discover what this material is.
The findings of this team are accompanied by the revelation that nickel vapour has also been discovered in the atmosphere of 2I/Borisov.
2I/Borisov: The Interstellar Intruder that keeps giving
The discovery that metal is also present in the atmosphere of the interstellar visitor 2I/Borisov was made by a team of astronomers in Poland. The team also used the VLT to catch a glimpse of the interstellar comet as it passed through the solar system.
The data collected with the VLT’s X-Shooter spectrograph revaled nickel vapour in the cold envlope surround 2I/Borisov.
ESO/L. Calçada/O. Hainaut, P. Guzik and M. Drahus
The discovery marks another surprise for astronomers, as again it details the discovery of sublimated heavy metals in a cold atmosphere.
“At first we had a hard time believing that atomic nickel could really be present in 2I/Borisov that far from the Sun,” says Piotr Guzik, the Jagiellonian University, Poland, a co-author on this second study. “It took numerous tests and checks before we could finally convince ourselves.”
This latter study shows that nickel was not uniquely present during the formation of our solar system, but as it can be seen in a comet from another planetary grouping, it may well be common in many such conglomerations.
“All of a sudden we understood that gaseous nickel is present in cometary atmospheres in other corners of the Galaxy,” Michał Drahus, also from the Jagiellonian University and another of the paper’s co-authors, says.
In unison, both these studies indicate that the comets of this solar system and the interstellar visitor 2I/Borisov share many similarities. Dahus adds: “Now imagine that our Solar System’s comets have their true analogues in other planetary systems — how cool is that?”
Jehin, meanwhile, believes these studies could inspire future research into cometary bodies and their atmospheres, and a re-examination of data already collected.
“Now people will search for those lines in their archival data from other telescopes,” the University of Liège researcher concludes. “We think this will also trigger new work on the subject.”
Astronomers have observed two pairs of quasars in the distant Universe, closer together than any previously observed examples of similar pairings. The team followed the discovery–made with the Hubble Space Telescope and Gaia spacecraft–with spectroscopic observations made by the Gemini North Telescope.
The discovery is significant as it points towards the possible existence of supermassive black hole (SMBH) pairs. As the quasar pairs exist in merging galaxies, the finding also grants researchers an insight into how such events could have proceeded in the early Universe.
It is the relatively close proximity between the quasars in the two pairings of just 10-thousand light-years that suggests to the astronomers that they belong to merging galaxies.
“We estimate that in the distant Universe, for every one thousand quasars, there is one double quasar,” says Yue Shen, an astronomer at the University of Illinois. “So finding these double quasars is like finding a needle in a haystack.”
Shen is the lead author of a paper published in the latest edition of the journal Nature Astronomy.
Quasars sit at the centre of galaxies in an area known as the active galactic nuclei (AGN) blasting out powerful jets of radiation. They are powered by SMBHs devouring material like gas and dust that surrounds them.
Quasars are so powerful that they profoundly affect the evolution of galaxies around them. This means that studying them is also a great way of learning how galaxies come together.
These particular quasars are 10-billion light-years from Earth meaning they existed just four billion years after the Big Bang. Double quasars are, in of themselves, rare, especially at such great distances. But, what makes these pairs particularly interesting is the fact they point to even rarer, hitherto undiscovered, SMBH binaries.
“This truly is the first sample of dual quasars at the peak epoch of galaxy formation that we can use to probe ideas about how supermassive black holes come together to eventually form a binary,” says Nadia Zakamska, Johns Hopkins University, part of the team that made the discovery.
The team’s discovery will excite scientists currently involved in the search for SMBH binaries. Current theories suggest that as monstrous as they are these black holes, which are believed to lurk at the centre of most galaxies, do not always exist in isolation.
Alessandra De Rosa is a research astrophysicist at the National Institute of Astrophysics, Italy, and the author of a recent review paper which summarizes what we know thus far about SMBH pairs.
“Searching for high z dual Active Galactic Nuclei at such small separations is a fundamental piece of information to understand how SMBHs could form and grow and to probe what we know about galaxy formation and evolution,” DeRosa, who was not involved in the team’s study, tells ZME Science. “Moreover, these systems are the most direct precursors of binary SMBHs which are amongst the loudest emitters of gravitational waves in the low-frequency ranges.”
DeRosa continues by explaining that the search for these objects at such great distances is extremely challenging due to instrument limitations that prevent them from being individually distinguished.
Until now it has been believed that these pairings would find the black holes in such close proximity that they could only be distinguished by the gravitational waves launched by their eventual merger.
This new research could offer another way to at least study how such SMBH pairings come together and form binaries.
Tracking Down Quasar Pairs
As DeRosa points out, tracking down these quasar pairs at a distance of around 10-billion years was no easy task. In order to do this, the astronomers employed a novel new method that unites data from several space-based and ground-based telescopes.
It takes an extremely powerful telescope to view objects at such distances limiting the team’s choice to the Gemini North telescope in Hawai’i, and the Hubble Space Telescope. Because observing time on these telescopes is extremely limited, sweeping the entire sky for quasar pairs was out of the question.
To work around this, the team selected 15 quasars from the 3D map created from data collected by the Sloan Digital Sky Survey (SDSS). Observations from the Gaia spacecraft were then used to narrow these 15 quasars to candidates that could actually be pairs.
The last step of the process was using Hubble to get a better look at these suspects. In this way, the team was able to confirm that two of the objects they selected were indeed quasar pairs.
Further investigation with Gemini North and its Gemini Multi-Object Spectrograph (GMOS) instrument allowed the astronomers to resolve the quasars’ individual spectra. Locked within this light signature is information regarding the distance from Earth and the quasars’ compositions.
“The Gemini observations were critically important to our success because they provided spatially resolved spectra to yield redshifts and spectroscopic confirmations simultaneously for both quasars in a double,” says Yu-Ching Chen, part of the team and a graduate student at the University of Illinois. “This method unambiguously rejected interlopers due to chance superpositions such as from unassociated star-quasar systems.”
The Next Steps for Studying Quasar Pairs
Whilst the team is extremely confident that they have discovered quasar pairs in merging galaxies, there does remain the slight chance that they have actually captured a double image of a single quasar.
This kind of doppelganger illusion can be caused by strong gravitational lensing, the bending of light from a distant source when an object of great mass passes between it and our line of sight.
In extreme cases, this lensing can cause objects to appear at multiple points in the sky due to light being forced to take different paths across the Universe. Striking examples are so-called Einstein crosses and rings when single light sources appear at numerous points in a geometrical pattern.
The researchers believe that this can be discounted in the case of their research as the light from the distant quasars did not pass an intersecting foreground galaxy.
The next step for the researchers is the research for more quasar pairs, hopefully leading to the development of a census of such duos in the early universe.
“This proof of concept really demonstrates that our targeted search for dual quasars is very efficient,” Hsiang-Chih Hwang, the principal investigator of the Hubble observations and a graduate at John Hopkins University, concludes. “It opens a new direction where we can accumulate a lot more interesting systems to follow up, which astronomers weren’t able to do with previous techniques or datasets.”
As an interstellar visitor–an object from outside the solar system–the rogue comet 2I/Borisov is already a source of great interest for astronomers. But researchers have now also discovered that this interstellar comet is composed of pristine material similar to that which exists when star systems first form.
Not only does this make 2I/Borisov even more exciting than previously believed, it means that studying the material that composes it and its coma –an envelope of gas and dust that surround comets– could unlock secrets of planetary system formation.
“2I/Borisov could represent the first truly pristine comet ever observed,” says Stefano Bagnulo of the Armagh Observatory and Planetarium, Northern Ireland, UK. The astronomer tells ZME Science: “We presume this is because it has travelled in the interstellar medium without interacting with any other stars before reaching the Sun.”
Bagnulo is the lead author of one of two papers published in the Nature family of journals detailing new in-depth analysis of 2I/Borisov.
Reflecting on 2I/Borisov
The team was able to make its detailed study of 2I/Borisov–the second interstellar comet found trespassing in our solar system after the cigar-shaped Oumuamua–using the Very Large Telescope (VLT) located in the Acatma Desert, Northern Chile.
In particular, they employed the FOcal Reducer and low dispersion Spectrograph (FORS2) instrument–a device capable of taking mages of relatively large areas of the sky with very high sensitivity–and a technique called polarimetry to unlock the comet’s secrets.
“Sunlight scattered by material, for instance, reflected by a surface, is partially polarised,” explains Bagnulo comparing this to polaroid sunglasses which absorb the polarised component of the light and thus dampen reflected light suppressing glare. “In astronomy, we are interested in that polarised radiation because it carries information about the structure and composition of the reflecting surface or scattering material.”
Bagnulo continues by explaining that because light reflected by a darker object is polarised more than the light reflected by a brighter object, polarimetry may be used to estimate the albedo of an asteroid. This makes it a tool regularly used to study comets and allowed the team to compare 2I/Borisov to comets that begin life in our solar system.
“We found that the polarimetric behaviour of 2I/Borisov is different than that of all other comets of our solar system, except for one, Comet Hale-Bopp,” Bagnulo says. “We suggest that this is because Hale-Bopp is a pristine comet.”
It also implies that 2I/Borisov and Halle-Bopp formed in similar environments, thus giving us a good picture of conditions in other planetary systems.
Whilst, Bagnulo and his team were conducting this research with data collected by the VLT, another team was using a different method to examine the material that comprises this interstellar comet.
The Secrets in the Dust of 2I/Borisov
Bin Yang, is an astronomer at ESO in Chile, who also took advantage of 2I/Borisov’s intrusion into the solar system to study this mysterious comet, but using the Atacama Large Millimeter/submillimeter Array (ALMA).
“I had the idea of observing the thermal emission from the dust particles in the coma of 2I/Borisov using ALMA. My co-author Aigen Li constructed theoretical models to fit the ALMA observation and set constraints on the dust properties,” Yang, the lead author of the second paper detailing the 2I/Borisov investigation, tells ZME Science. “The composition of 2I/Borisov is similar to solar system comets, consists of dust and various ices. The major ices are water ice, carbon monoxide ice and the minor species include hydrogen cyanide and ammonia.”
Yang goes on to explain that the team was not able to precisely determine the composition of 2I/Borisov’s dust component. The astronomer adds that it could be composed of silicates or carbonaceous materials or a mixture of both.
The team also found that the comet’s coma contains compact pebbles and grains of around 1mm and above.
Additionally, as 2I/Borisov neared the Sun the relative amounts of water and carbon they detected from it changed quite drastically.
“We found that the dust coma of Borisov consists of compact, millimeter-sized and larger pebble-like grains, which formed in the inner region near the central star,” Yang says. “We also found the cometary nucleus consists of components formed at different locations in its home system.”
“Our observations suggest that Borisov’s system exchanged materials between the inner regions and the outer regions that are far from the central star, perhaps due to gravitational stirring by giant planets much like in our own solar system.”
Bin Yang, ESO.
These characteristics indicate that 2I/Borisov formed by collecting materials from different locations in its own planetary system. It also imnplies that the system from which it originated likelty featured the exchange of materials between its inner and outer regions. Something that Yang says is also common in our solar system.
“So, it is possible that chaotic material exchanging processes are common phenomena for young planetary systems,” says Yang. “We want to know if other planetary systems form like our own. But we cannot study these systems to the level of their individual comets.”
“Interstellar objects represent the building blocks of planets around other stars. Comet Borisov provides a rare and valuable link between our own solar system and other planetary systems.”
The Journey of 2I/Borisov
2I/Borisov was first discovered by Gennedy Borisov, an amateur astronomer and telescope maker, in August 2019. It was only the second visitor from outside the solar system to be found within our planetary system. That means that as it passed the Sun it presented a unique opportunity to compare conditions in our small corner of the galaxy to those found in other planetary systems.
“2I/Borisov is quite a small comet and it didn’t get very close to the Earth and the Sun, so the emission from this comet is quite weak. We were happily surprised that we actually detected the thermal emission from this alien comet. Because of this detection, we are able to set constraints on the dust properties of this comet,” says Yang. “Comets in other planetary systems are simply too far away and too small to be seen by our telescopes.
“We are extremely lucky to find a comet that is from a planetary system far far away from us. Even more luckily, we managed to take many pictures and spectra of this alien comet during its short visit.”
Bin Yang, ESO.
As Yang points out, 2I/Borisov is only in our solar system for a short time before it must continue its interstellar journey, so the time available to astronomers to study it is limited. But, with interstellar visitors to the solar system believed to be fairly common, but difficult to spot, improving telescope technology could offer future opportunities to study other objects with similar interstellar origins.
Bagnulo points to both the upcoming Vera C Rubin telescope and ESA’s comet interceptor, set to launch in 2029, as future technology that could help us spot and investigate interstellar comets.
“We expect to detect at least one interstellar object per year,” Yang concludes. “So, we will have more opportunities to study alien materials.”
Using the Event Horizon Telescope (EHT) to observe the supermassive black hole at the centre of the galaxy Messier 87 (M87), astronomers have once again produced another first in the field of astronomy and cosmology.
Following up on the image of M87’s black hole published two years ago–the first time a black hole was imaged directly–astronomers at the EHT collaboration have captured a stunning image of the same black hole, this time in polarized light.
The achievement marks more than just an impressively sharp and clear second image of this black hole however–it also represents that first-time researchers have been able to capture the polarization of light around such an object.
Not only does this reveal details of the magnetic field that surrounds the supermassive black hole, but it also could give cosmologists the key to explaining how energetic jets launch from the core of this distant galaxy.
“M87 is a truly special object! It is tied for the largest black hole in the sky with the black hole in our galaxy–Sagittarius A*, ” Geoffrey C. Bower, EHT Project Scientist and assistant research astronomer at the Academia Sinica Institute of Astronomy and Astrophysics, tells ZME Science. “It’s about one thousand times further away but also one thousand times more massive.
“The M87 black hole’s home is in the centre of the Virgo Cluster, the nearest massive cluster of galaxies, each with its own black hole. This makes it a great laboratory for studying the growth of galaxies and black holes.”
Geoffrey C. Bower, Academia Sinica Institute of Astronomy and Astrophysics.
Along with Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor at Radboud University, Netherlands, Bower is one of the authors on two papers detailing the breakthrough published in the latest edition of The Astrophysical Journal Letters.
“We are now seeing the next crucial piece of evidence to understand how magnetic fields behave around black holes, and how activity in this very compact region of space can drive powerful jets that extend far beyond the galaxy,” says Mościbrodzka.
“We have never see magnetic fields directly so close to the event horizon,” the astronomer tells ZME Science.
“We now, for the first time, have information on how magnetic field lines are oriented close to the event horizon and how strong these magnetic fields are. All this information is new.”
Deeper Into the Heart of M87
The release of the first image of a black hole on the 10th of April 2019 marked a milestone event in science, and ever since then, the team behind that image has worked hard to delve deeper into M87’s black hole. This second image is the culmination of this quest. The observation of the polarized light allows us to better understand the information in that prior image and the physics of black holes.
“Light is an electromagnetic wave which has amplitude and direction of oscillation or polarization,” explains Mościbrodzka. “With the EHT we observed that light in the M87’s surrounding ring is polarized meaning that waves oscillation have a preferred direction.”
This polarization is a property of synchrotron radiation that is produced in the vicinity of this black hole. Polarization occurs when light passes through a filter–think of polarized sunglasses blocking out light and thus giving you a clearer view–thus the polarization of light in this picture accounts for this clearer view of M87’s black hole, which reveals a great deal of information about the black hole itself.
“The polarization of the synchrotron light tells us about the orientation of magnetic fields. So by measuring light polarization we can map out the magnetic fields around the black hole.”
Monika Mościbrodzka, Coordinator of the EHT Polarimetry Working Group and Assistant Professor, Radboud University
Capturing such an image of polarized light at a distance of 55 million light-years is no mean feat, and is only possible with the eight linked telescopes across the globe that comprise the EHT. Together these telescopes–including the 66 antennas of the Atacama Large Millimeter/submillimeter Array (ALMA)–form a virtual telescope that is as large as the Earth itself with a resolution equivalent to reading a business card on the Moon.
“As a virtual telescope that is effectively as large as our planet the EHT has a resolution power than no other telescope has,” says Mościbrodzka. “The EHT is observing the edge of what is known to humans, the edge of space and time. And for the second time, it has allowed us to bring to the public the images of this black hole.”
This image–as the above comparison shows– has had its clarity enhanced immensely by calibration with data provided by the Atacama Pathfinder EXperiment (APEX).
Of course, these magnetic fields are responsible for much more than just giving us a crystal clear image of the black hole they surround. They also govern many of the physical processes that make black holes such powerful and fascinating events–including one of M87’s most mysterious features.
How Magnetic Fields Help Black Holes ‘Feed’
The M87 galaxy–55 million light years from Earth– is notable for its powerful astrophysical jets that blast out of its core and extend for 5000 light-years. Researchers believe that these jets are caused when some of the matter at the edge of the black hole escapes consumption.
Whilst other matter falls to the surface of the central black hole and disappears to the central singularity, this escaping matter is launched into space as these remarkable jets.
Even though this is a more than plausible explanation, many questions still remain about the process, namely, how an area that is no bigger than our solar system creates jets that are greater in length than the entire galaxy that surrounds it.
This image of the polarized light around M87’s black hole which offers a glimpse into this inner region finally gives scientists a chance to answer these mysteries.
“Our planet’s magnetosphere prevents ionized particles emitted by the Sun from reaching the Earth’s surface. In the same way, strong black hole magnetic fields can prevent or slow down the accretion of matter onto the black hole,” Bowers says. “Those strong magnetic fields are also powerful for generating the jets of particles that flow at near the speed of light away from the black hole.”
By mitigating the feeding process of their central black holes, however, these magnetic fields may have an influence that like the jets they create may extend even further than M87 itself. They could be affecting the entire galactic cluster.
“Magnetic fields can play a very important role in how black holes ‘eat.’ If the fields are strong enough, they can prevent inflowing material from reaching the black hole. They are also important in funnelling matter out into the relativistic jets that burst from the black hole region. These jets are so powerful that they influence gas dynamics amongst the entire cluster of galaxies surrounding M87.”
Geoffrey C. Bower, Academia Sinica Institute of Astronomy and Astrophysics.
This means a better understanding of the magnetic fields around M87’s black hole also gives researchers an improved understanding of how the matter behaves at the edge of that black hole and perhaps of how such things affect neighbouring galaxies and their evolution.
And from the image of M87’s black hole the EHT team have developed, it looks clear that of the various models that cosmologists have developed to describe the interaction of matter at the edge of black holes, only those featuring strongly magnetized gases can account for its observed features.
“We have now a better idea about the physical process in the ring visible in the image,” Mościbrodzka says. “We now know more precisely how strong magnetic fields can be near a black hole. We also know more accurately at what rate the black hole is swallowing matter. And we have a better idea of what the black hole might look like in the future.”
In terms of what is next for black hole imaging, both Mościbrodzka and Bowers are clear; they have their sights set on a black hole that is closer to home than M87–the one that sits at the centre of the Milky Way, which despite being closer to home, could be a tougher nut to crack in terms of imaging.
“We’re hard at work on a problem that we know everyone wants to see; an image of the black hole at the centre of our galaxy,” says Bowers. “This is really tricky because the gas around the black hole moves so fast that the image may be changing on same the time scale that it takes to snap our picture. We think we know how to handle this problem but it requires a lot of technical innovation.”
Given the advancements already made by the EHT collaboration team, it would be unwise to bet against them achieving this lofty goal at some point in the not too distant future.
“We’ve gone from imagining what happens around black holes to actually imaging it!” Bowers concludes. “In the near future, we’ll be able to show a movie of material orbiting the black hole and getting ejected into a jet. I never thought I would see anything like this.
“Black holes are the simplest but most enigmatic objects in the Universe. These observations are just the beginning of the road to understanding them.”
Geoffrey C. Bower, Academia Sinica Institute of Astronomy and Astrophysics.
Using the aftermath of a comet collision in 1994 astronomers have measured the winds blowing across Jupiter‘s stratosphere for the first time. The team has discovered that these winds raging around the middle atmosphere of the solar system’s largest planet are incredibly powerful–reaching speeds of up to 400 metres per second at the poles.
The team’s findings represent a significant breakthrough in planetary metrology and mark the gas giant out as what the team are describing as a ‘unique metrological beast in the solar system.’
To conduct the research the astronomers diverged from the usual methods used to measure the winds of Jupiter. Previous attempts to measure the gas giant’s winds have hinged on measuring swirling clouds of gas–seen as the planet’s distinctive red and white bands–but this method is only effective in measuring winds in the lower atmosphere. Whereas, by using aurorae at Jupiter’s poles researchers have been able to model winds in the upper atmosphere. But, both of these methods, even when used in conjunction, have left the winds in the middle section of the gas giant’s atmosphere–the stratosphere– something of a mystery.
That is until now. This team of astronomers used the Atacama Large Millimetre Array (ALMA) to track molecules left in Jupiter’s atmosphere by the collision with the comet Shoemaker-Levy 9 in 1994.
“We had to use ALMA’s ability to quickly map Jupiter’s spectral emission at very high spatial and spectral resolution in the submillimeter and observe the Doppler shifts induced by the winds on the spectral line we targeted,” team leader Thibault Cavalié, Laboratoire d’Astrophysique de Bordeaux, France, exclusively tells ZME Science. “We could deduce the wind speeds just like you could deduce the speed of a passing fire engine by the change in frequency of its siren. This spectral line is formed in the stratosphere, giving us access to the winds at this altitude.
“It is the first time we achieve measuring directly winds in the stratosphere of Jupiter, which lacks visual tracers such as clouds.”
Thibault Cavalié, Laboratoire d’Astrophysique de Bordeaux, France.
Cavalié explains that the team had to use ALMA’s ability to quickly map Jupiter’s spectral emission at very high spatial and spectral resolution in the submillimeter and observe the Doppler shifts induced by the winds on the spectral line they targeted.
“We could deduce the wind speeds just like you could deduce the speed of a passing fire engine by the change in frequency of its siren,” the researcher continues. “This spectral line is formed in the stratosphere, giving us access to the winds at this altitude.”
What the astronomers discovered was powerful winds in the middle atmosphere of Jupiter in two different locations. One set of winds conformed to expectations, but the other came as a surprise.
Jupiter’s ‘Supersonic Jet’ Winds
Cavalié explains that the team first found a 200 metres per second eastward jet just north of the equator in ‘super-rotation–meaning that the wind rotates faster around the planet than the planet rotates itself. “Winds at such latitudes were expected from models and previous temperature measurements at these low latitudes,” the astronomer adds.
But, not everything observed by the team conformed to expectations.
“Most surprisingly, we identified winds located under the main UV auroral emission near Jupiter’s poles. These winds have velocities of 300 to 400 meters per second,” Cavalié says. “While the equatorial winds were kind of anticipated, the auroral winds and their high speed were absolutely unexpected.”
To put this into perspective, the fastest winds ever recorded on earth reached a speed of just 103 metres per second–measured at the Mount Washington Observatory in 1931. These auroral winds even beat the winds recorded in Jupiter’s Great Red Spot–an ongoing raging storm on the surface of the gas giant–which have been clocked at around 120 metres per second.
The speed of these jets isn’t their only intimidating quality, however. The jets seem to behave like a giant vortex with a diameter around four times that of our entire planet, reaching a height of around 900 kilometres.
“A vortex of this size would be a unique meteorological beast in our Solar System.”
Thibault Cavalié, Laboratoire d’Astrophysique de Bordeaux, France.
The team’s measurements and stunning discovery, documented in a paper published in the latest edition of Astronomy & Astrophysics, wouldn’t have been possible without a violent incident in Jupiter’s recent history.
Shoemaker-Levy 9 Still has Impact
The impact of Shoemaker-Levy 9 upon the surface of Jupiter was an event–or more precisely a series of events– that had already made history before its effects made this research possible.
The comet broke up in the planet’s atmosphere resulting in a series of impacts that had never been studied prior to 1994, and its somewhat ironic that thanks to this study, Shoemaker-Levy 9 is still having an impact today. The comet left traces of hydrogen cyanide swirling in Jupiter’s atmosphere which the team was able to track.
“The team measured the Doppler shift of hydrogen cyanide molecules — tiny changes in the frequency of radiation emitted by the molecules — caused by their motion driven by stratospheric winds on Jupiter,” says Thomas K Greathouse, Senior Research Scientist at Southwest Research Institute (SwRI), responsible for the development of the study and analysis of the observational results. “
“The high spectral and spatial resolution and the exquisite sensitivity of the observations at the wavelengths covered by ALMA allowed us to map such small Doppler shifts caused by the winds in the stratosphere all along the limb of Jupiter.”
Thomas K Greathouse, Senior Research Scientist at Southwest Research Institute (SwRI).
The fact that the team was able to obtain all the measurements they did with just 30 minutes of operating time with ALMA is a striking testament to the power and precision of the 66 antennas that make up the telescope array located in the Atacama Desert of Nothern Chile, currently the most powerful radio telescope on Earth.
“It was the availability of ALMA that made these measurements possible. Previous radio observatory facilities did not have the combination of spectral and spatial resolution along with the high sensitivity needed to measure the winds as was done in this study,” Greathouse tells ZME Science. “Making further observations using ALMA to capture Jupiter at different orientations will allow us to study these winds in more detail and allow us to look for temporal variability in them as well.
“Additionally, more extensive measurements will be possible from the JUICE mission and its Submillimetre Wave Instrument slated for launch in 2022.”
The Future of Jupiter Investigations
JUICE or JUpiter ICy moons Explorer is the first large-class mission in the European Space Agency’s (ESA) Cosmic Vision program and will arrive at Jupiter in 2029 when it will begin a three-year mission observing the gas giant in intense detail.
“This is why science is so much fun. We have worked hard to understand a system–Jupiter’s stratosphere in this case–as best we can, we make our predictions about something–stratospheric wind behaviour–and then go test those predictions. If we are right, fantastic, we move on to the next problem, but if we are wrong we have learned something new and unique and can then continue making further studies to come to a more complete understanding of the system.”
Thomas K Greathouse, Senior Research Scientist at Southwest Research Institute (SwRI).
For Cavalié, who has been involved with the measurement of Jupiter’s winds since 2009, the future is bright for such investigations and what they can tell us about the solar system’s largest planet and gas giants in general. “We now want to use ALMA again to characterize the temporal variability of the equatorial winds,” the astronomer says. “It is expected from temperature measurements and models that the direction of the equatorial winds should oscillate from eastward to westward with a period of about 4 years.”
The scientist is also clear, just because he and his colleagues have achieved a first, that doesn’t mean they are prepared to rest on their laurels. There are a lot of exciting developments on the way, and thus a lot of work to be done.
“We also want to observe the auroral winds during a Juno perijove pass to compare our data with observations of the poles by the spacecraft to better understand their origin and what maintains them,” he explains. “In addition, this study is a stepping stone for future investigations to be conducted using the same technique with JUICE and its Submillitre Wave Instrument.”
In addition to these missions, the ESO’s Extremely Large Telescope (ELT)–due to start operations later this decade–will also join investigations of Jupiter and should be capable of providing highly detailed investigations of the gas giant’s atmosphere.
“Jupiter and the giant planets are fascinating worlds. Understanding how these planets formed and how they work is a source of daily motivation, especially when working with world-class observatories like ALMA and participating in space missions to explore Jupiter and its satellites.”
Thibault Cavalié, Laboratoire d’Astrophysique de Bordeaux, France.
Using the Hubble Space Telescope astronomers have spotted an important and extraordinary event in planetary evolution for the first time. The researchers have observed volcanic activity on a distant rocky planet reforming that world’s atmosphere.
The planet–GJ 1132 b–is believed by the team to have previously possessed an atmosphere that was stripped by the intense radiation emitted by the bright young red dwarf star it closely orbits. After its thick blanket of hydrogen and helium was expunged the planet was left as a rocky core roughly the size of Earth.
The astronomers believe that much of the hydrogen from GJ 1132 b’s initial atmosphere was absorbed by the exoplanet’s molten magma mantle creating a reservoir of the element which is now being slowly dispersed back into the atmosphere. This dispersal replenishes hydrogen being lost to space.
The fact that the planet’s volcanic activity is generating a secondary atmosphere that is replacing the first has come as a huge suprise to the researchers.
What makes this replacement atmosphere so interesting and useful to astronomers is the fact that has come from the planet’s interior. Thus its chemical composition–with abundant hydrogen, hydrogen cyanide, methane and ammonia with glimmers of a hydrocarbons–means that astronomers should be able to study the interior of the exoplanet by proxy.
“This second atmosphere comes from the surface and interior of the planet, and so it is a window onto the geology of another world,” explains Paul Rimmer, University of Cambridge, UK, who was part of the team that made the discovery. “A lot more work needs to be done to properly look through it, but the discovery of this window is of great importance.”
The finding could change the way we think about highly irradiated exoplanets which astronomers normally expect to lack atmospheres. “We first thought that these highly radiated planets would be pretty boring because we believed that they lost their atmospheres,” explains Raissa Estrela of the Jet Propulsion Laboratory at the California Institute of Technology in Pasadena, California, USA, another member of the research team. “But we looked at existing observations of this planet with Hubble and realised that there is an atmosphere there.”
Like Earth, But Really Different
Whilst sharing some similarities with Earth, GJ 1132 b is actually a very different world. GJ 1132 b has a similar density, size and age–around 4.5 billion years. Additionally, both planets started life as molten balls of rock with hydrogen-dominated atmospheres. But, whereas our planet was able to hang on to its atmosphere, the intense radiation GJ 1132 b was exposed to stripped that world’s gaseous envelope.
The differences become more extreme when considering the formation of both worlds. GJ 1132 b is the surviving core of a sub-Neptune exoplanet–a planet resembling Neptune but with a smaller mass–so didn’t start its life as a terrestrial world like we believe Earth did. Possibly the most extreme difference between the two worlds, however, is their relationships with their respective parent stars.
Whilst Earth orbits the Sun at a comfortable distance, rotating on its axis as it does so, GJ 1132 b orbits its red dwarf parent star in blisteringly close proximity. So-close that the exoplanet’s orbit period is just 36 hours. That isn’t the only major orbital difference, however. GJ 1132 b is tidally locked, meaning that the same face points towards its parent star throughout its orbit.
This isn’t the only source of heating the exoplanet is experiencing. The tidal force that the planet experiences due to its proximity to its parent star and that star’s gravitational force is permanently stretching and squeezing it.
This deformation is converted to heat beneath the planet’s surface, maintaining its mantle’s molten state. It could be this tidal heating that is driving the extreme volcanism and also causing the planet’s thin crust to crack, allowing hydron to escape and replenish the atmosphere.
The findings raise the question; how many of the terrestrial worlds we see are actually the stripped cores of sub-Neptunes?
“How many terrestrial planets don’t begin as terrestrials? Some may start as sub-Neptunes, and they become terrestrials through a mechanism whereby light evaporates the primordial atmosphere,” says Mark Swain of NASA’s Jet Propulsion Laboratory who led the research. “This process works early in a planet’s life when the star is hotter. Then the star cools down and the planet’s just sitting there.”
“So you’ve got this mechanism that can cook off the atmosphere in the first 100 million years, and then things settle down. And if you can regenerate the atmosphere, maybe you can keep it.”
The observations made by the team were part of the Hubble observing program and raise the interesting possibility that if this secondary atmosphere is thin enough, astronomers could actually see down to the surface of the exoplanet.
“This result is significant because it gives exoplanet scientists a way to figure out something about a planet’s geology from its atmosphere,” concludes Rimmer. “It is also important for understanding where the rocky planets in our own Solar System — Mercury, Venus, Earth and Mars, fit into the bigger picture of comparative planetology, in terms of the availability of hydrogen versus oxygen in the atmosphere.”
With assistance from the ESO’s Very Large Telescope (VLT), astronomers have discovered the most distant radio emission ever recorded. The source is a quasar so distant that its light has been travelling 13 billion years to reach us. That means that it existed when the Universe was just 780 or so million years old.
The object–named P172+18–is what astronomers term a ‘radio loud’ quasar, shining powerfully in the radio-frequency region of the electromagnetic spectrum, extremely bright due to the powerful jets emitted from its axis. Radio loud quasars are fairly rare with only 10% of discovered quasars fitting this description.
This makes the team’s finding even more extraordinary as even though more distant quasars have been found, it marks the first time that researchers have been able to identify the tell-tale signs of powerful radio-bright jets at such incredible cosmic distances.
Excitingly, the team at the centre of this finding believe that this is just the tip of the iceberg with regards to radio-loud quasars, with many more yet to be discovered. Possibly even some at much greater distances.
The team’s discovery is discussed in a paper published in the latest edition of The Astrophysical Journal.
Quasars: Powered By Black Holes
Quasars are objects that lie at the centre of galaxies, powered by supermassive black hole ‘engines.’ The black hole at the heart of P172+18 is a doozy. The team estimate it is around 300 million times the mass of the Sun. As impressive as that is, perhaps more staggering is the rate at which this supermassive black hole is consuming gas and dust.
“The black hole is eating up matter very rapidly, growing in mass at one of the highest rates ever observed,” says Chiara Mazzucchelli, co-leader of the project and an astronomer based at ESO, Chile. “I find it very exciting to discover ‘new’ black holes for the first time, and to provide one more building block to understand the primordial Universe, where we come from, and ultimately ourselves.”
The team believes that the rapid rate of gas consumption displayed by the supermassive black hole and its burgeoning growth are both intrinsically linked to the emission of the radio bright jets they detected. The jets could be disturbing gas in an accretion disc around the black hole, causing it to fall into the central black hole at an accelerated rate.
If this proves to be the case, the study of radio-loud quasars could be of vital importance in the future investigation of the growth of black holes in the infant Universe. There is currently some confusion as to how supermassive black holes could have grown to tremendous sizes over a relatively short-period in cosmic terms, thus a mechanism that accounts for rapid growth is a boon to cosmologists fearing that models of cosmic evolution could need fundamental revision.
Very Loud and Very Far Away
P172+18 was first spotted as a radio source in data gathered by t the Magellan Telescope at Las Campanas Observatory in Chile. Mazzucchelli and team co-leader Eduardo Bañados of the Max Planck Institute for Astronomy, Germany, then assessed the data and quickly concluded that the radio source represented jets produced by a distant radio-loud quasar.
“As soon as we got the data, we inspected it by eye, and we knew immediately that we had discovered the most distant radio-loud quasar known so far,” says Bañados.
Because P172+18 was only observed for a brief period, it was necessary for the duo to follow up the observations with other telescopes. They were able to do this with the use of the X-Shooter instrument associated with the VLT, based in the Atacama Desert, Chile, as well as the National Radio Astronomy Observatory’s Very Large Array (VLA) in New Mexico, and the Keck Telescope located near the summit of Mauna Kea, Hawaii.
These follow-up observations allowed the team to ascertain a wealth of details about the quasar and the supermassive black hole powering it, including its mass and the rapid rate at which it is consuming gas and surrounding matter.
P172+18 may currently hold the record for most distant radio-loud quasar, but it is not a distinction that Mazzucchelli and Bañados think it will hang on to for long. The duo believes that many more radio-loud quasars are lurking in the Universe waiting to be discovered and that undoubtedly, some of these will exist at greater distances than 13 billion light-years.
Whilst these may be a challenge to spot currently, the ESO’s forthcoming Extremely Large Telescope (ELT), currently under construction in Northern Chile, should be powerful enough to handle such observations.
“This discovery makes me optimistic and I believe — and hope — that the distance record will be broken soon,” concludes Bañados.
An international team of astronomers has discovered a nearby exoplanet orbiting a red dwarf star that is perfect for deeper investigation. In particular, this exoplanet could be a prime target for precise atmospheric measurements, something that, for planets outside the solar system, has so-far eluded astronomers.
The team’s findings documenting the discovery of this relatively close super-Earth–so-called because they have a mass greater than our planet but still lower than planets like Uranus and Neptune which are classified as ‘ice giants’–are published in the latest edition of the journal Science.
The team discovered Gliese 486 b whilst surveying 350 small red dwarf stars for signs of low-mass planets using the CARMENES spectrograph mounted on the 3.5m telescope at the Calar Alto Observatory telescope, Spain. The exoplanet was found due to the ‘wobble’ it caused in the orbit of its parent star.
“Our team is searching primarily for Earth-like and super-Earth planets orbiting nearby stars. In this case, we have found a nearby super-Earth, just 26 light-years away orbiting a small star every 1.5 or so Earth days,” Karen Collins, an astronomer at the Center for Astrophysics, Harvard & Smithsonian, and a co-author on the paper tells ZME Science. “We were certainly excited to have found a transit signal in the light curve of a star that is so close to the Sun in astronomical terms.
“We quickly realized that Gliese 486 b, with radial velocity mass measurements in hand, would likely become a prime target for additional detailed follow-up studies, particularly atmospheric investigations.”
Karen Collins, Center for Astrophysics, Harvard & Smithsonian
These investigations could include searching for the conditions necessary for life, or even for biomarkers left behind by simple lifeforms.
Colins continues by explaining that it is Gliese 486 b’s proximity–it is the third closest transiting exoplanet yet to be uncovered– that, amongst other things like its temperature, makes it a good candidate for more in-depth study. “Because Gliese 486 b is so close to the solar system, relative to most known transiting exoplanets, we may be able to probe the atmosphere of the planet using the upcoming James Webb Space Telescope and possibly other telescopes,” she explains.
That is, of course, if it actually has an atmosphere.
What We Know About Gliese 486 b So Far…
Whilst the team of astronomers may not yet be certain that Gliese 486 b has an atmosphere, there are some things that they do know about the exoplanet and its red dwarf home star.
“It is only about 30% larger than Earth but has a mass of about 2.8 times that of our planet,” study author Trifon Trifonov, Max Planck Institute for Astronomy, explains to ZME Science. The researcher adds that models suggest that the exoplanet’s composition is similar to Venus and Earth, including a metallic core. “Anyone standing on Gliese 486 b would feel a gravitational pull that is about 70% stronger than what we experience on Earth.”
In addition to being denser than the earth, Gliese 486 b is also much hotter according to Trifon. This is because the exoplanet revolves around its host star on a circular orbit every 1.47 days, with one side permanently pointing towards its parent star.
“The proximity to the red dwarf Gliese 486 heats the planet significantly, making its landscape hot and dry, interspersed with volcanos and glowing lava rivers,” Trifon says. “There are quite a few super-Earth type exoplanets already discovered. All of these exoplanets are exceptional on their own. In this context, the physical characteristics of Gliese 486 b are not uncommon. However, the proximity of Gliese 486 b, allowed us to measure its mass with unprecedented precision, thanks to observations done with the CARMENES and the MAROON-X instruments.”
From the information the astronomers do possess regarding Gliese 486 b, especially its mass, Collins adds that the clues it also has an appreciable atmosphere are in place.
“Because we do know that the planet surface gravity is relatively high–about 70% stronger than Earth–we believe that there is a chance the planet may have retained an appreciable atmosphere.”
Karen Collins, Center for Astrophysics, Harvard & Smithsonian
Using NASA’s Transiting Exoplanet Survey Satellite (TESS) spacecraft the astronomers were able to deduce that Gliese 486 b periodically crosses the stellar disk of its parent red dwarf star, a rare and fortuitous event.
“For transiting planets like Gliese 486 b, we have two primary methods to probe the atmospheres, if they exist,” Collins continues. “Transit spectroscopy allows us to study the planet’s atmosphere as the planet passes in front of the star from the telescope’s perspective.”
Collins says that should the exoplanet possess an atmosphere part of the light from its parent star that reaches our telescopes will have been filtered through this. This means that the light profile filtered by the atmosphere can be compared to an unfiltered version when the planet is not in front of the star.”By comparing the in-transit spectrum of the star with a spectrum of the star when the planet is not transiting, we can isolate atmospheric signals from the planet and possibly detect some of the components of the atmosphere.”
The second method detailed by Collins involves the detection of radiation directly from an exoplanet’s hot surface as it occupies different orbital phases across the star’s face. The emission spectrum that gives this technique its name–emission spectroscopy–reveals characteristic traits that indicate the presence of certain elements emitting and absorbing light in the exoplanet’s atmosphere.
“Its temperature of around 700 Kelvin makes it suitable for emission spectroscopy and phase curve studies in search of an atmosphere,” adds Trifonov.
The Golden Age of Exoplanet Science
Concluding our interview I ask Collins and Trionov if we are entering a ‘Golden Age’ for exoplanet science. They are both quick to correct me. “I would say we are living in it!” Trinov exclaims. “During the past three decades, astronomers have discovered thousands of exoplanets, and the number is increasing daily.
“Every day, we enhance our knowledge about the physical properties of exoplanets, their formation, and evolution.”
Trifon Trifonov, Max Planck Institute for Astronomy
Collins is equally assured that exoplanet science is in its prime, but adds that there is no decline in sight. “Frankly, I believe we have been in the golden age of exoplanet science for over a decade now,” the astronomer says. “Even so, with the advent of TESS to discover and measure the size of nearby small transiting planets, precise radial velocity machines like that of the CARMENES consortium and the MAROON-X instrument to measure their masses, and soon the James Webb Space Telescope to investigate their atmospheres, it’s fair to say that we are entering the golden age of well-characterized small planet exoplanet science.”
And Collins is clear how lucky she regards herself for just being involved with astronomy at this crucial juncture in its history. “I am excited to be involved in the search for and characterization of Earth-sized and Super-Earth planets such as Gliese 486 b,” says explains enthusiastically. “Precise atmospheric measurements are likely around the corner! What will this relatively new scientist from a small but progressive astrophysics program at a school in Kentucky be involved with next? Will we soon discover an Earth twin with an Earth-like atmosphere or even signs of life in an atmosphere?
“It is almost as if I’m living in a series of Star Trek. I can’t wait to see what we discover next!”
Karen Collins, Center for Astrophysics, Harvard & Smithsonian