Category Archives: Remote sensing

Archaeologists uncover hidden citadel in ancient Maya city

Using airborne data, a group of archaeologists discovered a previously unknown structural complex near the Maya city of Tikal, in what is now Guatemala. While the city is notable in itself, what makes the discovery even more interesting is that the complex’s structures are similar to buildings in Teotihuacan, a Mesoamerican city. 

View of the Teotihuacan Complex at Tikal. Image credit: Researchers

The ruins of Tikal have been the subject of extensive study since the 1950s, with researchers documenting details of every structure and cataloguing all excavated items. This has made Tikal one of the best understood archeological sites in the world. Nevertheless, there’s always something new to discover — as we can see in this study. 

Stephen Houston from Brown University and Thomas Garrison from the University of Texas have discovered that what was thought to be a natural hilly area near Tikal’s center was actually a neighborhood of ruined buildings intentionally designed to look like Teotihuacan, the most powerful and largest city there was in ancient Americas.

“What we had taken to be natural hills actually were shown to be modified and conformed to the shape of the citadel,” Houston said in a statement. “Regardless of who built this smaller-scale replica and why, it shows without a doubt that there was a different level of interaction between Tikal and Teotihuacan than previously believed.”

Understanding Tikal

The area where the complex was found hadn’t been explored until now as researchers believed that the hills were just part of the natural landscape. Houston and Garrison used LIDAR, a light detection and ranging technology, to build 3D models of the surface and identify structural features. This was followed then by an on-site exploration that confirmed the findings.

In the area, which is roughly 62 acres, the researchers confirmed with excavations that the buildings were built with mud plaster than limestone, a material usually used by the Maya society. In fact, the structures appeared to be scaled-down versions of the buildings from Teotihuacan’s citadel, located more than 1,000 kilometers (621 miles) away. 

The researchers also found human remains near the replicated buildings. The bodies were surrounded by several funerary items such as animal bones and projectile points. There was also plenty of coal, suggesting the assemblage was deliberately set on fire – a death ritual that is similar to the one used with warriors at the citadel of Teotihuacan. 

It’s not the first-time evidence is found of the influence of Teotihuacan in Tikal, as contacts between the two societies were common. Maya elites lived and traded in Teotihuacan. But after centuries of peace, Teotihuacan conquered Tikal in 378 CE.  The new findings suggest a more intense contact between the two, the researchers argue.

“The architectural complex we found very much appears to have been built for people from Teotihuacan or those under their control,” Houston said. “Perhaps it was something like an embassy complex, but when we combine previous research with our latest findings, it suggests something more heavy-handed, like occupation or surveillance.”

The study was published in the journal Antiquity. 

A neural network has learned to identify tree species from satellite

A detailed land-cover map showing forest in Chiapas state in southern Mexico. The map was produced using Copernicus Sentinel-2 optical data from 14 April 2016. The image is not part of the discussed study.

Much of what we know about forest management comes from aerial photos nowadays. Whether it’s drones, helicopters, or satellites, bird’s-eye views of forests are crucial for understanding how our forests are faring — especially in remote areas that are hard to monitor on the ground.

Satellite imagery, in particular, offers a cheap and effective tool for monitoring. But the problem with satellite data is that oftentimes, the resolution is pretty low, and it can be hard to tell what you’re looking at.

But a new study using neural networks to distinguish between satellite imagery may help with that.

Hierarchical model structure/Svetlana Illarionova et al., IEEE Journal of Selected Topics in Applied Earth Observations and Remote Sensing.

“Commercial forest taxation providers and their end-users, including timber procurers and processors, as well as the forest industry entities can use the new technology for quantitative and qualitative assessment of wood resources in leased areas. Also, our solution enables quick evaluations of underdeveloped forest areas in terms of investment appeal,” explains Svetlana Illarionova, the first author of the paper and a Skoltech PhD student.

Illarionova and her colleagues from the Skoltech Center for Computational and Data-Intensive Science and Engineering (CDISE) and Skoltech Space Center used a neural network to automate dominant tree species’ identification in high and medium resolution images.

Classes markup of the study area. Image credits: Illarionova et al.

After training, the neural networks were able to identify the dominant tree species in the test site from Leningrad Oblast, Russia. The data was confirmed with ground-based observations during the year 2018. A hierarchical classification model and additional data, such as vegetation height, helped further enhance the predictions’ quality while improving the algorithm’s stability to facilitate its practical application.

The study focused on identifying the dominant species. Of course, among the forests with different compositions, there will be forests where the distribution is roughly equal between two or even more species, but the compositions of these mixed forests was outside the scope of the study.

“It is worth noting that the “dominant species” in forestry does not exactly match the biological term “species” and is connected mostly with the timber class and quality,” the researchers write in the paper.

Overall, the algorithm appeared capable of identifying the dominant species, although the researchers note that the outcome can be improved by a better training markup, which they plan on doing in future research

“However, in future research, we are going to cover mixed forest cases, which will fall entirely into the hierarchical segmentation scheme. The other goal is to add more forest inventory characteristics, which can also be estimated from the satellite imagery,” the study concludes.

Satellite images show the massive extent of August’s wildfires

It’s been a scorching summer, and it’s no coincidence. With climate change in almost full swing, the odds of heatwaves and fires increase dramatically — and we’re seeing the effects. The European Union’s Copernicus observation program has published a collage of just some of these fires, as seen from space. Here are some of them.

Wildfires in north-eastern Algeria

Credit: European Union, Copernicus Sentinel-2 imagery.

This 3D visualization shows one of the dozens of fires ravaging through the Kabylia region in Algeria. Thousands of fires have broken out in the Mediterranean, and over 100 of them are in the Kabylia region, where there have been  65 casualties to date.

Algerians have decried the lack of governmental support as the fires rip through the country.

“We started raising funds and volunteering during the last COVID-19 wave, so a lot of organisational mechanisms were already in place to fight these fires,” said Mokrane Nessah, a 54-year-old coordinator for one of the charities on site.

Wildfire in Evia, Greece

Credit: European Union, Copernicus Sentinel-2 imagery.

Evia is the second-largest Greek island, and these two images taken just ten days apart show how the island was devastated by wildfires. Thousands of residents were evacuated, and after tireless firefighter work, the fire was contained only after seven days.

Carbon monoxide pollution from wildfires on North America’s West Coast

Credit: European Union, Copernicus Sentinel-5P imagery.

Many of the dreadful effects of wildfires are visible to the naked eye — but not all. Heatwaves across North America have fueled massive wildfires (so-called “megafires”). According to data from the Copernicus Atmosphere Monitoring Service, these megafires have triggered massive carbon dioxide emissions. Many of these fires are still not contained.

Smoke cloud from fires in Amazonia

Credit: European Union, Copernicus Sentinel-3 imagery.

Every year, the fire season in the Amazon peaks in August-September. While some fires are natural, in recent years, the phenomenon is greatly exacerbated by burning of vegetation for deforestation. Recently, the Brazilian Institute of Space Research (INPE) recorded the second-highest annual deforestation rate ever. According to its data, in the period between August 2020 and July 2021, Brazil has lost 8,712 km² of forests, or about 12 times the area of New York City. 

This smoke cloud is visible from some of the areas most affected by deforestation — the states of Rondônia, Mato Grosso, and Para.

Wildfire in Var, France

Credit: European Union, Copernicus Sentinel-2 imagery.

The Mediterranean basin has been hit by one of its most severe heatwaves in history. A fire broke out in south-eastern France, causing thousands to evacuate their homes or holiday sites. In the image above, the fire scar is still visible, while active fires still output smoke.

More fires in Greece

Credit: European Union, Copernicus Sentinel-2 imagery.

Greece is having a particularly painful wildfire year. The image above shows a fire in Peloponnese, also fueled by intense heatwaves and strong winds. Heatwaves cause leaves and wood to be drier and more flammable.

Credit: European Union, Copernicus Sentinel-3 imagery.

Meanwhile, in western Attica, very strong winds are making firefighter intervention much more difficult.

Wildfire near Castro Marim – Portugal

Credit: European Union, Copernicus Sentinel-2 imagery.

This image shows the massive burnt scar that resulted from wildfires in the Faro District, in southern Portugal. The wildfire is now under control, but it shows that Portugal is also vulnerable in the face of summer fires.


The bottom line: wildfires and global warming go hand in hand

The relationship between climate and fire is complex, but researchers are increasingly finding strong correlations between warm summer temperatures and large fire years. Since climate change is making heatwaves more likely, the logical conclusion is that fires will become more and more common (and more and more massive) as climate change starts to take its toll.

For instance, in the south-eastern US, models suggest that a warming of just one degree Celsius would increase the burned area by as much as 600% in some types of forests.

Of course, hotter weather doesn’t automatically bring wildfires — you also need ignition, and in many parts of the world, the majority of fires are started by humans. In the US, for instance, 84% of fires are started by humans

However, once a fire starts, hot weather can make the difference between an easily contained fire and a large-scale catastrophe — and this is pretty much what we’re seeing over the course of this summer.

Martian buried lakes may actually just be clay

This image taken by NASA’s Mars Reconnaissance Orbiter shows ice sheets at Mars’ south pole. The spacecraft detected clays nearby this ice; scientists have proposed such clays are the source of radar reflections that have been previously interpreted as liquid water. Credit: NASA/JPL-Caltech/University of Arizona/JHU

Where there’s water, there’s life — but Mars may not be as watery as we thought. We already knew that liquid water can’t really last on the surface: it would evaporate in no time. We also knew that water ice is plentiful in some areas on Mars. But what about liquid water?

Based on observations in 2018, astronomers started to suspect that Mars may have underground lakes beneath some masses of ice. This was based on observations from a radar instrument aboard the ESA (European Space Agency) Mars Express orbiter.

The idea isn’t as crazy as it sounds. Earth also has a lot of underground water, and even frozen moons like Europa or Ganymede are thought to have large masses of subsurface water. Mars having a subsurface lake below its ice cap wouldn’t be all that weird — especially as the data seemed to back it up.

But the data may not back it up after all.

The south pole on Mars — frozen, but maybe not as rich in subsurface water. Image credits: ESA.

Radar instruments send out pulses of electromagnetic waves; the wave passes through different materials (in this case, the layers of Mars), and based on the electromagnetic properties of the material, a receiver captures the reflected waveform.

The initial analysis of this radar data showed some strong reflections, which researchers interpreted as bodies of water. But in a new study, Isaac Smith of Toronto’s York University now has a different idea.

Smith didn’t go to Mars or anything like that — he worked in a lab, freezing clays with liquid nitrogen, until they reached temperatures like those on Mars.

Isaac Smith of Toronto’s York University bundled up while working in a lab, freezing smectite clays with liquid nitrogen to test how they respond to radar signals. The results have challenged the hypothesis that subsurface lakes can be found at Mars’ south pole.
Image credits: York University/Craig Rezza

“The lab was cold,” Smith said. “It was winter in Canada at the time, and pumping liquid nitrogen into the room made it colder. I was bundled up in a hat, jacket, gloves, scarf, and a mask because of COVID-19. It was pretty uncomfortable.”

The clays in this case are called “smectites” — a type of rock formed by liquid water long time ago. He then subjected them to radar instruments similar to those used on Mars, to see their response. It was exactly like what the Mars Orbiter observed.

In a recent paper published in Geophysical Research Letters, researchers found that many of the “water” signals came from areas close to the surface, where it should be too cold for water to remain liquid, even when mixed with minerals commonly found on Mars (that can lower freezing temperature of water).

The colored dots represent sites where bright radar reflections have been spotted by ESA’s Mars Express orbiter at Mars’ south polar cap. Such reflections were previously interpreted as subsurface liquid water, but their prevalence and proximity to the frigid surface suggest they may be something else. Image credits: Credits: ESA/NASA/JPL-Caltech.

So we know that it’s probably too cold for liquid water to exist in those areas, and we have another likely candidate that could be responsible for the signal. Although it’s not yet possible to directly confirm whether what was on the radar data was liquid water, smectites, or maybe even something else, water is looking less and less likely.

But this is a win for science. Ultimately, the fact that researchers are able to derive so much information about a different planet, working with so little data, is remarkable.

“In planetary science, we often are just inching our way closer to the truth,” said Jeffrey Plaut of NASA’s Jet Propulsion Laboratory. “The original paper didn’t prove it was water, and these new papers don’t prove it isn’t. But we try to narrow down the possibilities as much as possible in order to reach consensus.”

Computer simulation of gravitational wave emissions S. Ossokine, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes project, W. Benger (Airborne Hydro Mapping GmbH)

What are Gravitational Waves?

Whilst it may not have the snappiest name, the event GW150914 is pretty significant in terms of our understanding of the Universe. This event, with a name that includes ‘GW’ as a prefix which is an abbreviation of ‘Gravitational Wave’ and the date of observation–15/09/14– marked humanity’s first direct detection of gravitational waves.

This was groundbreaking on two fronts; firstly it successfully confirmed a prediction made by Albert Einstein’s theory of general relativity almost a century before. A prediction that stated events occurring in the Universe do not just warp spacetime, but in certain cases, can actually send ripples through this cosmic fabric.

Numerical simulation of two inspiralling black holes that merge to form a new black hole. Shown are the black hole horizons, the strong gravitational field surrounding the black holes, and the gravitational waves produced ( S. Ossokine, A. Buonanno (Max Planck Institute for Gravitational Physics), Simulating eXtreme Spacetimes project, W. Benger (Airborne Hydro Mapping GmbH)).

The second significant aspect of this observation was the fact that it represented an entirely new way to ‘see’ the Universe, its events and objects. This new method of investigating the cosmos has given rise to an entirely new form of astronomy; multimessenger astronomy. This combines ‘traditional’ observations of the Universe in the electromagnetic spectrum with the detection of gravitational waves, thus allowing us to observe objects that were previously invisible to us.

Thus, the discovery of gravitational waves truly opened up an entirely new window on the cosmos, but what are gravitational waves, what do they reveal about the objects that create them, and how do we detect such tiny tremblings in reality itself?

Gravitational Waves: The Basics

  • Gravitational waves are ripples in the fabric of spacetime.
  • These ripples travel from their source at the speed of light.
  • The passage of gravitational waves squash and stretch space itself.
  • Gravitational waves can be detected by measuring these infinitesimally small changes in the distance between objects.
  • They are created when an object or an event that curves spacetime causes that curvature to change shape.
  • Amongst the causes of gravitational waves are colliding black holes and neutron stars, supernovae, and stars that are undergoing gravitational collapse.

Theoretical Underpinnings

Imagine sitting at the side of a lake, quietly observing the tranquil surface of the water undisturbed by nature, the wind, or even by the slightest breeze. Suddenly a small child runs past hurling a pebble into the lake. The tranquillity is momentarily shattered. But, even as peace returns, you watch ripples spread from the centre of the lake diminishing as they reach the banks, often splitting or reflecting back when they encounter an obstacle.

The surface of the lake is a loose 2D analogy for the fabric of spacetime, the pebble represents an event like the collision of two black holes, and our position on Earth is equivalent to a blade of grass on the bank barely feeling the ripple which has diminished tremendously in its journey to us.

Poincaré and Einstein both saw the possibility of gravitational waves propagating through space-time at the speed of light

Gravitational waves were first predicted by Henri Poincare in 1905 as disturbances in the fabric of spacetime that propagate at the speed of light, but it would take another ten years for the concept to really be seized upon by physicists. This happened when Albert Einstein predicted the same phenomenon as part of his revolutionary 1916 geometric theory of gravity, better known as general relativity.

Whilst this theory is most well-known for suggesting that objects with mass would cause warping of spacetime, it also went a step further positing that an accelerating object should change this curvature and cause a ripple to echo through spacetime. Such disturbances in spacetime would not have been permissible in the Newtonian view of gravity which saw the fabric of space and time as separate entities upon which the events of the Universe simply play out.

But upon Einstein’s dynamic and changing stage of united spacetime, such ripples were permissible.

Gravitational waves arose from the possibility of finding a wave-like solution to the tensor equations at the heart of general relativity. Einstein believed that gravitational waves should be generated en masse by the interaction of massive bodies such as binary systems of super-dense neutron stars and merging black holes.

The truth is that such ripples in spacetime should be generated by any accelerating objects but Earth-bound accelerating objects cause perturbations that are far too small to detect. Hence why our investigations must turn to areas of space where nature provides us with objects that are far more massive.

As these ripples radiate outwards from their source in all directions and at the speed of light, they carry information about the event or object that created them. Not only this, but gravitational waves can tell us a great deal about the nature of spacetime itself.

Where do Gravitational Waves Come From?

There are a number of events that can launch gravitational waves powerful enough for us to detect with incredibly precise equipment here on Earth. These events are some of the most powerful and violent occurrences that the Universe has to offer. For instance, the strongest undulations in spacetime are probably caused by the collision of black holes.

Other collision events are associated with the production of strong gravitational waves; for example the merger between a black hole and a neutron star, or two neutron stars colliding with each other.

But, a cosmic body doesn’t always need a partner to make waves. Stellar collapse through supernova explosion–the process that leaves behind stellar remnants like black holes and neutron stars– also causes the production of gravitational waves.

A simulation of gravitational waves emitted by a binary pulsar consisting of two neutron stars

To understand how gravitational waves are produced, it is useful to look to pulsars–binary systems of two neutron stars that emit regular pulses of electromagnetic radiation in the radio region of the spectrum.

Einstein’s theory suggests that a system such as this should be losing energy by the emission of gravitational waves. This would mean that the system’s orbital period should be decreasing in a very predictable way.

The stars draw together as there is less energy in the system to resist their mutual gravitational attraction, and as a result, their orbit increases in speed, and thus the pulses of radio waves are emitted at shorter intervals. This would mean that the time it takes for the radio wave to be directly facing our line of sight would be reduced; something we can measure.

This is exactly what was observed in the Hulse-Taylor system (PSR B1913±16), discovered in 1974, which is comprised of two rapidly rotating neutron stars. This observation earned Russell A. Hulse and Joseph H. Taylor, Jr, both of Princeton University, the 1993 Nobel Prize in Physics. The reason given by the Nobel Committee was: “for the discovery of a new type of pulsar, a discovery that has opened up new possibilities for the study of gravitation.”

An animation illustrating how gravitational waves are emitted by two neutron stars as they orbit each other eventually colliding (credit: NASA/Goddard Space Flight Center).

Though inarguably an impressive and important scientific achievement, this was still only indirect evidence of gravitational waves. Whilst the effect Einstein predicted of shortening of the pulsar’s spin was definitely present, this wasn’t an actual direct detection.

In fact, though not alive to witness this momentous achievement, Einstein had predicted that this would be the only way we could ever garner any hint of gravitational waves. The great physicist believed those spacetime ripples would be so faint that they would remain impossible to detect by any technological means imaginable at that time.

Fortunately, Einstein was wrong.

How do we Detect Gravitational Waves?

It should come as no surprise that actually detecting a gravitational wave requires a piece of equipment of tremendous sensitivity. Whilst the effect of gravitational waves–the squashing and stretching space itself–sounds like something that should pre-eminently visible, the degree by which this disturbance occurs is so tiny it is totally imperceptible.

Fortunately, there is a branch of physics that is pretty adept at deal with the tiny. To spot gravitational waves, researchers would use an effect called interference, something demonstrated in the most famous quantum physics experiment of all time; the double-slit experiment.

Physicists realised that a laser interferometer could be used to measure the tiny squashing and stretching of space as it would cause the arms of the equipment to shrink by a minute amount. This means when splitting a laser and sending it through the arms of an interferometer the squeezing of space caused by the passage of a gravitational wave would cause one laser to arrive slightly ahead of the other–meaning they are out of phase and causing destructive interference. Thus, this difference in arrival times causes interference that gives an indication that gravitational waves have rippled across one of the arms.

But, not just any laser interferometer would do. Physicists would need an interferometer so large that it constituents a legitimate feat in engineering. Enter the Laser Interferometer Gravitational-wave Observatory (LIGO).

Schematic showing how LIGO works. (Johan Jarnestad/The Royal Swedish Academy of Sciences)

The LIGO detector uses two laser emitters based at the Hanford and Livingstone observatories, separated by thousands of kilometres apart to form an incredibly sensitive interferometer. From these emitters, lasers are sent down the ‘arms’ of the interferometer which are actually 4km long vacuum chambers.

This results in a system that is so sensitive it can measure a deviation in spacetime that is as small as 1/10,000 the size of an atomic nucleus. To put this into an astronomical context; it is equivalent to spotting a star at a distance of 4.2 light-years and pinpointing its location to within the width of a human hair! This constitutes the smallest measurement ever practically attempted in any science experiment.

And in 2015, this painstaking operation paid off.

On 14th September 2015, the LIGO and Virgo collaboration spotted a gravitational wave signal emanating from the spiralling in and eventual merger of two black holes, one 29 times the mass of the Sun, the other 36 times our star’s mass. From changes in the signal received the scientists were also able to observe the resultant single black hole.

The signal, named GW150914, represented not just the first observation of gravitational waves, but also the first time humanity had ‘seen’ a binary stellar-mass black hole system, proving that such mergers could exist in the Universe’s current epoch.

Different Kinds of Gravitational Waves

Since the initial detection of gravitational waves, researchers have made a series of important and revelatory detections. These have allowed scientists to classify different types of gravitational waves and the objects that may produce them.


Continuous Gravitational Waves

A single spinning massive object like a neutron star is believed to cause a continuous gravitational wave signal as a result of imperfections in the spherical shape of this star. if the rate of spin remains constant, so too are the gravitational waves it emits–it is continuously the same frequency and amplitude much like a singer holding a single note. Researchers have created simulations of what an arriving continuous gravitational wave would sound like if the signal LIGO detected was converted into a sound.

The sound of a continuous gravitational wave of the kind produced by a neutron star can be heard below.

(SXS Collaboration)

Compact Binary Inspiral Gravitational Waves

All of the signals detected by LIGO thus far fit into this category as gravitational waves created by pairs of massive orbiting objects like black holes or neutron stars.

The sources fit into three distinct sub-categories:

  • Binary Black Hole (BBH)
  • Binary Neutron Star (BNS)
  • Neutron Star-Black Hole Binary (NSBH)


Each of these types of binary pairing creates its own unique pattern of gravitational waves but shares the same overall mechanism of wave-generation–inspiral generation. This process occurs over millions of years with gravitational waves carrying away energy from the system and causing the objects to spiral closer and closer until they meet. This also results in the objects moving more quickly and thus creating gravitational waves of increasing strength.

The ‘chirp’ of an eventual merger between neutron stars has been translated to sound waves and can be heard below.

Max Planck Institute for Gravitational Physics
(Albert-Einstein-Institut)

Stochastic Gravitational Waves

Small gravitational waves that even LIGO is unable to precisely pinpoint could be passing over Earth from all directions at all times. These are known as stochastic gravitational waves due to their random nature. At least part of this stochastic signal is likely to have originated in the Big Bang.

Should we eventually be able to detect this signal it would allow us to ‘see’ further back into the history of the Universe than any electromagnetic signal could, back to the epoch before photons could freely travel through space.

The simulated sound of this stochastic signal can be heard below.

(R. Williams (STScI), the Hubble Deep Field Team, NASA)

It is extremely likely given the variety of objects and events in the Universe that other types of gravitational wave signals exist. This means that the quest to detect such signals is really an exploration of the unknown. Fortunately, our capacity to explore the cosmos has been boosted tremendously by our ability to detect gravitational waves.

A New Age of Astronomy

GW150914 conformed precisely to the predictions of general relativity, confirming Einstein’s most revolutionary theory almost exactly six decades after his death in 1955. That doesn’t mean that gravitational waves are done teaching us about the Universe. In fact, these ripples in spacetime have given us a whole new way to view the cosmos.

Before the discovery of gravitational waves, astronomers were restricted to a view of the Universe painted in electromagnetic radiation and therefore our observations have been confined to that particular spectrum.

Using the electromagnetic spectrum alone, astronomers have been able to discover astronomical bodies and even the cosmic microwave background (CMB) radiation, a ‘relic’ of one of the very first events in the early universe, the recombination epoch when electrons joined with protons thus allowing photons to begin travelling rather than endlessly scattering. Therefore, the CMB is a marker of the point the universe began to be transparent to light.

Yet despite the strides traditional astronomy has allowed us to make in our understanding of the cosmos, the use of electromagnetic radiation is severely limited. It does not allow us to directly ‘see’ black holes, from which light cannot escape. Nor does it allow us to see non-baryonic, non-luminous dark matter, the predominant form of matter in galaxies–accounting for around 85% of the universe’s total mass. As the term ‘non-luminous’ suggests dark matter does not interact with the electromagnetic spectrum, it neither absorbs nor emits light. This means that observations in the electromagnetic spectrum alone will never allow us to see the majority of the matter in the universe.

Clearly, this is a problem. But one that can be avoided by using the gravitational wave spectrum as both black holes and dark matter do have considerable gravitational effects.

Gravitational waves also have another significant advantage over electromagnetic radiation.

This new form of astronomy measures the amplitude of the travelling wave, whilst electromagnetic wave astronomy measures the energy of the wave, which is proportional to the amplitude of the wave squared.

Therefore the brightness of an object in traditional astronomy is given by 1/distance² whilst ‘gravitational brightness’ falls off by just 1/distance. This means that the visibility of stars persists in gravitational waves for a much greater distance than the same factor persists in the electromagnetic spectrum.

Of course, none of this is to suggest that gravitational wave astronomy will ‘replace’ traditional electromagnetic spectrum astronomy. In fact the two are most powerful when they are unified in an exciting new discipline–multimessenger astronomy

Sources and Further Reading

Maggiore. M., Gravitational Waves: Theory and Experiments, Oxford University Press, [2019]

Maggiore. M., Gravitational Waves: Astrophysics and Cosmology, Oxford University Press, [2019]

Collins. H., Gravity’s Kiss:  The Detection of Gravitational Waves, MIT Press, [2017]

Look Deeper, LIGO, [https://www.ligo.caltech.edu/page/look-deeper]

Ingenuity helicopter makes its first one-way flight on Mars

It came, it saw, it conquered — after four successful return flights, Ingenuity (the first man-made machine to take flight on another planet) is now embarking on a new adventure: flying from place to place, accompanying the Perseverance rover, and studying Mars from above.

Ingenuity flying, as seen by Perseverance. Image credits: NASA / JPL.

There’s a drone *on Mars*

Ingenuity was meant to be just a proof of concept, a stepping stone for future missions. But it already is more than just that.

After having its Wright Brothers moment and taking off in a rarefied atmosphere (the Martian atmosphere is just 1% as dense as that on the Earth), it carried out three more flights, each longer than the previous. For each of these flights, though, it went in one direction and then returned to its original launch area (named after the Wright Brothers).

The fifth flight was different, though. After rising up to 33 feet (10 meters) and capturing high-resolution color images of its new neighborhood, it went south and safely landed at a new location.

“We bid adieu to our first Martian home, Wright Brothers Field, with grateful thanks for the support it provided to the historic first flights of a planetary rotorcraft,” said Bob Balaram, chief engineer for Ingenuity Mars Helicopter at JPL. “No matter where we go from here, we will always carry with us a reminder of how much those two bicycle builders from Dayton meant to us during our pursuit of the first flight on another world.”

The view from a helicopter on Mars. Image credits: NASA / JPL.

A new step

The flight marks a transition to a new phase in its mission. This will focus on assessing what capabilities such a device can provide, especially as a complement to the Perseverance rover. The helicopter can scout and provide detailed aerial imaging, information that could greatly benefit future exploration missions on Mars. The rover-helicopter duo will work together to unlock unprecedented research capability.

So far, everything is going according to plan — which, when you’re working remotely with instruments on another planet, is already a fantastic achievement. But in some regards, Ingenuity is even surpassing what its engineers had hoped for.

“The power system that we fretted over for years is providing more than enough energy to keep our heaters going at night and to fly during the day,” a NASA press release mentioned. “The off-the-shelf components for our guidance and navigation systems are also doing great, as is our rotor system. You name it, and it’s doing just fine or better.”

Of course, at any point, something could go wrong. After all, Ingenuity has fulfilled its original mission and is now trying on an extended schedule (proof that even on Mars, those that work well are assigned overtime).

NASA engineers are fully aware of the risks, and they’re taking things step by step.

“We will now be flying over unsurveyed terrains and transfer to airfields that are not well characterized so there’s a higher probability of a bad landing,” explained MiMi Aung, Ingenuity’s project manager.

“We will be celebrating each day that ingenuity survives and operates beyond the original window.”

“The plan forward is to fly Ingenuity in a manner that does not reduce the pace of Perseverance science operations,” said Balaram. “We may get a couple more flights in over the next few weeks, and then the agency will evaluate how we’re doing. We have already been able to gather all the flight performance data that we originally came here to collect. Now, this new operations demo gives us an opportunity to further expand our knowledge of flying machines on other planets.”

Still, it’s hard to not get excited at the prospect of a helicopter assisting a rover to explore another planet. It’s barely been a century since the first human flight, and now we’re already sending flying devices to other planets. Just a few decades ago, this would have seemed like science fiction more than an actual possibility — yet here we are.

We hope to be reporting on Ingenuity for a long time.

This image shows an artist’s impression of what the surface of the 2I/Borisov comet might look like.  2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (SO/M. Kormesser)

Interstellar visitor 2I/Borisov is the most pristine comet ever observed

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.

This image was taken with the FORS2 instrument on ESO’s Very Large Telescope in late 2019, when comet 2I/Borisov passed near the Sun. Since the comet was travelling at breakneck speed, around 175 000 kilometres per hour, the background stars appeared as streaks of light as the telescope followed the comet’s trajectory. The colours in these streaks give the image some disco flair and are the result of combining observations in different wavelength bands, highlighted by the various colours in this composite image. (ESO/O. Hainaut)
This image was taken with the FORS2 instrument on ESO’s Very Large Telescope in late 2019 when comet 2I/Borisov passed near the Sun. Since the comet was travelling at breakneck speed, around 175 000 kilometres per hour, the background stars appeared as streaks of light as the telescope followed the comet’s trajectory. The colours in these streaks give the image some disco flair and are the result of combining observations in different wavelength bands, highlighted by the various colours in this composite image. (ESO/O. Hainaut)

“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).

This image shows an artist’s impression of what the surface of the 2I/Borisov comet might look like.     2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (SO/M. Kormesser)
This image shows an artist’s impression of what the surface of the 2I/Borisov comet might look like.  2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (SO/M. Kormesser)

“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.

This image shows an artist’s close-up view of what the surface of the comet might look like.  2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (ESO/M. Kormesser)
This image shows an artist’s close-up view of what the surface of the comet might look like.  2I/Borisov was a visitor from another planetary system that passed by our Sun in 2019, allowing astronomers a unique view of an interstellar comet. While telescopes on Earth and in space captured images of this comet, we don’t have any close-up observations of 2I/Borisov. It is therefore up to artists to create their own ideas of what the comet’s surface might look like, based on the scientific information we have about it. (ESO/M. Kormesser)

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.”

Jupiter’s Supersonic Stratospheric Winds Make it a Unique Beast

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.’

This image shows an artist’s impression of winds in Jupiter’s stratosphere near the planet’s south pole, with the blue lines representing wind speeds. These lines are superimposed on a real image of Jupiter, taken by the JunoCam imager aboard NASA’s Juno spacecraft. (ESO/L. Calçada & NASA/JPL-Caltech/SwRI/MSSS)

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.

This image, taken with the MPG/ESO 2.2-metre telescope and the IRAC instrument, shows comet Shoemaker–Levy 9 impacting Jupiter in July 1994. (ESO)

“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).
Amazing image of Jupiter taken in infrared light on the night of 17 August 2008 with the Multi-Conjugate Adaptive Optics Demonstrator (MAD) prototype instrument mounted on ESO’s Very Large Telescope. This false colour photo is the combination of a series of images taken over a time span of about 20 minutes, through three different filters. 9ESO/F. Marchis, M. Wong, E. Marchetti, P. Amico, S. Tordo)

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.



Astronomers witness the ‘death’ of a galaxy

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

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

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

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

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

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

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

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

Annagrazia Puglisi, Centre for Extragalactic Astronomy, Durham University

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

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

Galactic Collisions and Tidal Tails

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

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

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

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

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

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

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


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

Serendipity and a Series of Firsts

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

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

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

Annagrazia Puglisi, Centre for Extragalactic Astronomy, Durham University

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

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

“The numbers didn’t just add up.”

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

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

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

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

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

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

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

Original research:

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

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

Primordial black holes could hide a multiverse of possibilities

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

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

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

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

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

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

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

Primordial Black holes and Lingering Mysteries

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

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

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

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

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

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

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

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

 Searching the Early Universe for Primordial Black Holes

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

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

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

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

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

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

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

Fortunately the HSC fits the bill.

The Hyper Suprime-Cam sees the Big Picture

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

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

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

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

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

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

Original Research

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

Water Found on the Moon’s Sunlit Surface

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

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

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

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

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

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

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

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

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

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

How Much Water Have NASA Found?

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

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

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

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

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

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

SOFIA–So Good

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

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

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

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

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


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

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

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


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

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

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

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

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

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

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It's getting crowded up there. A plot of space debris around the Earth. (NASA)

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

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

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

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

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

Being Evasive

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

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

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

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

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

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

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

Fun with Lasers

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

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

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

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

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

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

How satellite data can help us save struggling forests

Forests first lose their resilience, and then they succumb to environmental stress. If we can detect the former, we have a chance of stopping the later.

Forests are under threat from multiple angles. Image credits: National Park Service.

The Amazon fires drew the world’s eyes to the drama unfolding in many of the world’s forests, but that was just a glimpse — a singular tragic wave in an ever-growing tide of threats that forests must face.

It’s not just deforestation — although that is a very dangerous threat in and of itself. Episodes of forest mortality have been widely observed in recent
decades, owed largely to urbanization and climate change.

Changing temperature and precipitation patterns are some of the most direct consequences of climate change. These changes place more stress on forests, a process which has accentuated in recent decades. Oftentimes, by the time forests start to fall, it is too late for intervention. Predicting this process is important, but it is also challenging, as the underlying mechanisms are not well understood.

In a new study, Yanlan Liu, Mukesh Kumar and colleagues from Cambridge University, produced a new, observational approach for predicting forest mortality.

Remote sensing is already a common technique in vegetation monitoring. Image credits: NASA.

The key is using remote sensing data of vegetation dynamics. Already, remote sensing (the process of detecting and monitoring the physical characteristics of an area by measuring its reflected and emitted radiation) is already a common approach in environmental monitoring. However, researchers say that they could use the technique to detect important tipping points that predict forest mortality, such as when shrubland starts to take over areas with trees. Essentially, this timing coincides with the moment forests start to lose their resilience.

The authors tested their approach in Californian forests and reported significant success: their early warning signal detected extreme forest stress 6-19 months before irreversible damage. This signal was detected prior to other signs of forest decline, such as reduced greenness.

This extra time could offer forestry organizations a chance to intervene in time and save the forest.

This is not a trivial issue — it’s a crucial aspect if we want to ensure a sustainable future for the planet and human society. Forests help stabilize the climate. They regulate ecosystems, protect biodiversity, play an integral part in the carbon cycle, support livelihoods, and can help drive sustainable growth. Around a quarter of the world’s population rely on forests for their livelihoods

The study “Reduced resilience as an early warning signal of forest mortality” has been published in Nature Climate Change. https://doi.org/10.1038/s41558-019-0583-9

Leaf.

Earth’s green history may help scientists spot plant life on alien planets

A team of researchers plans to use the Earth’s history to spot plantlife on other planets.

Leaf.

Image via Pixabay.

By analyzing the Earth’s evolution over time, a team of astronomers has found a template fingerprint that points to the presence of vegetation on alien planets. This fingerprint would thus help tease out potentially-habitable planet in the far reaches of space. Even better, the method can also be used to determine the age of the planet in question and the evolutionary level reached by its flora.

The old that is strong does not wither

“Our models show that Earth’s vegetation reflectance signature increases with coverage of our planet’s surface, but also with the age of our planet,” said co-author Jack O’Malley-James, research associate in astronomy at Cornell University’s Carl Sagan Institute.

Earth’s surface has gone through some dramatic changes over the course of its life. During the last 500 million years, for example, our planet has gained (and subsequently lost) a sprawling ice cover, and was covered in deep forests.

The first plants to ever colonize dry land were tiny and relatively simple — mosses. They could only establish a tentative hold on the planet’s surface, which would present a very weak biosignature to observers on a far-away planet. Compared to that, today’s lush forests and rolling grasslands impart the Earth with an obvious biosignature.

That discrepancy, in a nutshell, is what the team relies on to search for life on other planets.

“We use Earth’s history as a key for finding life in the universe,” said co-author Lisa Kaltenegger, associate professor of astronomy at Cornell University and director of the Carl Sagan Institute.

“Our work shows that as plants evolved on Earth, the vegetation signal that reveals their presence became stronger, making older exoplanets really interesting places to look for vegetation.”

Researchers first got a taste of the signature life imparts on a planet back in 1989, when NASA’s Galileo craft left for Jupiter. Carl Sagan, then an astronomer at Cornell, requested that the craft’s instruments be trained on Earth to analyze the wavelengths of light reflected by a life-rich planet. Analysis of this data revealed a distinctive spike in reflectance between the red and infrared spectrum — just beyond the limit of what our eyes can perceive — due to vegetation.

“The signal Galileo detected for Earth was similar to what observations of an exoplanet in another star system might look like, but, of course, Galileo was much closer to us,” adds O’Malley-James. “Observing an exoplanet is more challenging, but telescope technology is getting better at spotting tiny signals. And factoring Earth’s changing landscapes into our models will make it easier to detect vegetation in the future on other worlds.”

Despite our technological advancements, planets with rich floras would be the easiest to spot than those with more sparse vegetation, the team concludes.

The paper “The Vegetation Red Edge Biosignature Through Time on Earth and Exoplanets” has been published online in the journal Astrobiology.

History in the making: Japan lands two rovers on asteroid

After days of gripping suspense, the two small rovers finally landed on the Ryugu asteroid — and they’ve even sent a few postcards back home.

This photo shows the view from asteroid Ryugu from the Minerva-II1A. The probe is one of two that landed on Ryugu from the Japanese Aerospace Exploration Agency’s Hayabusa2 spacecraft. It’s the first time two mobile rovers landed on an asteroid. The image is blurred because it was taken during the rover’s descent. Credit: Japan Aerospace Exploration Agency.

The rovers are part of Japan Aerospace Exploration Agency’s Hayabusa2 asteroid sample-return mission. They were deployed from the spacecraft and successfully landed on Ryugu, and both are still in good condition.

In order to perform the deployment, the Hayabusa2 carefully lowered itself carefully down toward the surface, until it was only 55 meters (180 ft) above. Then, after the rovers were deployed, the shuttle went back up to 20 km (12.5 mi) above the asteroid.

Because Ryugu is so small and doesn’t have a significant gravitational field, the landing was particularly difficult, but this also allows the rovers to hop around the asteroid, taking photos as they go.

The 1kg rovers are equipped with wide-angle and stereo cameras, and are powered internal rotors, which propel the robots across the asteroid. The rovers also feature sensors that measure the surface temperatures, and Hayabusa2 itself carries sensors for remote sensing and sampling.

[panel style=”panel-default” title=”Underwater palace.” footer=””]Ryugu is an asteroid which measures approximately 1 kilometer (0.6 mi) in diameter. Ryugu was discovered in 1999, and its name refers to Ryūgū (Dragon Palace), a magical underwater palace in a Japanese folktale. In the story, a fisherman Urashima Tarō travels to the palace on the back of a turtle, and when he returns, he carries with him a mysterious box — something which is alluding to Hayabusa2 returning with samples[/panel]

Animation of Hayabusa2 orbit from 3 December 2014 to 29 December 2019.

But while this is already a remarkable achievement, the mission is still far from being over: the Japanese space agency still has two more deployments to complete — a larger rover called MASCOT in October and another tiny hopper next year. Then, the rovers have to collect samples, and board the shuttle again, returning to Earth for lab analysis. If everything goes according to plan, the shuttle will leave Ryugu in 2019 and will return back to Earth in 2020.

So far, the asteroid’s surface was rougher than expected, which brought another layer of difficulty to the mission. The surface is blackish-colored, and the asteroid has maintained its original composition for eons, as Ryugu is a particularly primitive asteroid type. Studying it could shed light on the origin and evolution of Earth and even the solar system. For now, we eagerly await the next mission checkpoints.

Florence wide lens 2.

Astronaut tweets incredible pictures of Hurricane Florence heading for the US East Coast

From the lens of Alexander Gerst, a German astronaut currently aboard the ISS, comes a dire warning: “Watch out, America!”

Grest (Twitter link), who joined the International Space Station crew back in June, tweeted some awesome and terrifying pictures of Hurricane Florence sprawled over the planet under his feet. “Watch out, America!”, the tween also warned, “this is a no-kidding nightmare coming for you”.

Eye of the storm

Hurricane Florence is currently a Category 4 storm making a beeline for the US East coast. The storm’s effects are predicted to make themselves felt throughout South and North Carolina starting Thursday, according to the National Hurricane Center.

Undeniably enormous, and frightfully powerful, the storm has captured the imagination of astronauts watching over it from orbit. Grest shot multiple pictures of the storm and posted them online for all the world to see its beauty and fury both.

Florence wide lens.

Image credits Alexander Gerst / ESA via Twitter.

Florence wide lens 2.

Image credits Alexander Gerst / ESA via Twitter.

The storm is so massive, Gerst explained in his Tweet, that he “could only capture her with a super wide-angle lens”. Hurricane Florence is currently over 500 miles (804 kilometers) in diameter.

Gerst also used a high-power telephoto lens to zoom in on the storm’s eye as the station passed overhead.

Storm eye 1.

Image credits Alexander Gerst / ESA via Twitter.

Storm eye 2.

Image credits Alexander Gerst / ESA via Twitter.

Storm eye 3.

Image credits Alexander Gerst / ESA via Twitter.

“Get prepared on the East Coast,” Gerst warned when Tweeting the photo.

NASA also recorded “stark and sobering” video footage of Florence from the space station on Wednesday:

SETI project uses AI to track down mysterious light source

Credit: Breakthrough Listen.

Last year, astronomers tasked with hunting alien signals identified 21 repeating light pulses emanating from a dwarf galaxy located 3 million-light years away. The source could be a fast-rotating neutron star — or it could be alien technology, perhaps meant to propel a space-sailing craft. Now, the researchers used artificial intelligence to pore through the dataset to discover 72 new fast radio bursts generated by the mysterious light source.

Fast radio bursts (FRBs) are bright pulses of radio emission mere milliseconds in duration. The signals acquired by the Green Bank Telescope in West Virginia and then initially analyzed through traditional methods by the Breakthrough Listen — a SETI project led by the University of California, Berkeley — lasted only an hour.

What sets the source in question — called FRB 121102 — apart from other on-off fast radio bursts is that the emitted bursts fired in a repeated pattern, alternating between periods of quiescence and frenzied activity.

Since the first readings made on August 26, 2017, the team of astronomers has devised a machine-learning algorithm that scoured through 400 terabytes of data recorded over a five-hour-long period.

The machine learning algorithm called a “convolutional neural network” is often employed by tech companies to display online search results or sort images. It found an additional 72 bursts not detected originally, bringing the total number of detected bursts from FRB 121102 to around 300 since it was initially discovered in 2012.

“This work is exciting not just because it helps us understand the dynamic behavior of fast radio bursts in more detail, but also because of the promise it shows for using machine learning to detect signals missed by classical algorithms,” said Andrew Siemion, director of the Berkeley SETI Research Center and principal investigator for Breakthrough Listen, the initiative to find signs of intelligent life in the universe.

The mystery still lingers, though. We still don’t know much about FRBs or what produced this sequence, but the new readings help put some new constraints on the periodicity of the pulses generated by FRB 121102. It seems like the pulses are not fired all that regularly after all, at least not if the pattern is longer than 10 milliseconds. More observations might one day help scientists figure out what is driving these enigmatic light sources, the authors of the new study wrote in The Astrophysical Journal.

“Whether or not FRBs themselves eventually turn out to be signatures of extraterrestrial technology, Breakthrough Listen is helping to push the frontiers of a new and rapidly growing area of our understanding of the Universe around us,” said UC Berkeley Ph.D. student Gerry Zhang.

Jupiter magnetic field.

Jupiter’s magnetic field is extremely bizarre, potentially due to unknown processes in its core

Jupiter’s magnetic field is crazy!

Jupiter, Io.

Jupiter and Io, one of its many moons.
Image via Pixabay.

The first map of the Jovian magnetic field has been compiled by an international team of researchers — and heads are still being scratched over it. The gas giants’ magnetic field is unlike anything we’ve ever seen before, hinting at unknown processes going on beneath its surface.

King of the gods

It didn’t come as much of a surprise to any researcher that Jupiter’s magnetic field is in a class of its own. While the gas giant boasts 11 times the diameter of our planet, it’s magnetic field is over 20,000 times as strong. It’s also much larger and has several complex features that have no counterpart in our own planet’s magnetic signature. These features, as far as we can tell, may stem from Jupiter’s rapid rotation and large liquid metallic hydrogen interior.

New data beamed back by the Juno spacecraft — which is still busy orbiting around the planet’s poles — allowed researchers from the US and Denmark to study this magnetic field much more closely than ever before. Starting from this data, which was recovered during eight orbits, they mapped the magnetic field in unprecedented detail at depths up to 10,000 kilometers (6,214 miles). Instead of making things more clear, however, the wealth of data only created further confusion. Take a look:

Jupiter magnetic field.

Image credits Moore et al., 2018, Nature.

Jupiter’s magnetic field emerges from a broad area close to its North pole (red on the image above) and re-enters around the South pole — so far, not especially surprising. What is very surprising, however, is that part of the magnetic field re-enters through a highly concentrated region just south of the equator — an area the team calls the Great Blue Spot.

The field is much weaker outside of these areas (grey-blue in the image above).

Earth’s magnetic field is dipolar. The field emerges from the South pole, re-enters through the North pole, and runs through the center of the planet. There are small non-dipolar components, but they’re relatively evenly spread out across the two hemispheres and they’re nowhere near as massive as the Great Blue Spot.

None of it prepared us for Jupiter’s hectic magnetic display.

“Before the Juno mission, our best maps of Jupiter’s field resembled Earth’s field,” planetary scientist Kimberly Moore of Harvard University told Newsweek. “The main surprise was that Jupiter’s field is so simple in one hemisphere and so complicated in the other. None of the existing models predicted a field like that.”

Juptier magnetic full.

Image credits

The lop-sided nature of Jupiter’s magnetic field points to yet-undiscovered processes under the surface. Magnetic fields are the product of churning flows of conductive liquids inside a planet. As the planet rotates, these liquids create magnetic fields — just like a dynamo.

Earth’s ‘dynamo’ is encased by a solid crust; the team believes their results suggest Jupiter’s dynamo lacks this casing. One of the models they propose envisions Jupiter’s core not as a solid, but as a slush — a mixture of rock and ice partially dissolved in liquid metallic hydrogen. Such a structure could create layers that would result in an asymmetrical magnetic field, they explain.

Another possibility would be that helium rains on the planet work to destabilize the field. This scenario, however, fails to satisfactorily explain the asymmetry seen in the magnetic field.

Juno is still orbiting Jupiter and will continue for quite some time. The team hopes to use further observations to better understand the magnetic field they’ve uncovered.

The paper “A complex dynamo inferred from the hemispheric dichotomy of Jupiter’s magnetic field” has been published in the journal Nature.

NASA finds ice on the Moon — raising prospects of a lunar colony

For the first time, scientists have found irrefutable evidence of ice on the lunar surface. To make things even more exciting, this makes the prospect of establishing a lunar colony much more likely.

The image shows the distribution of surface ice at the Moon’s south pole (left) and north pole (right), detected by NASA’s Moon Mineralogy Mapper instrument. Blue represents the ice’s location, plotted over an image of the lunar surface. Grayscale corresponds to surface temperature (darker representing colder areas and lighter shades indicating warmer zones). The ice is concentrated along the darkest and coldest locations, in the shadows of craters. This is the first time scientists have definitive evidence of water ice on the Moon’s surface. Credits: NASA

In 1835, a journalist working for The Sun (a New York newspaper), published a series of articles in which he claimed that life on the Moon had been discovered. He went on to say that winged humanoids and goat-like creatures inhabited the Moon, attributing the findings to Sir John Herschel, one of the greatest astronomers of the time. The articles, however, were a hoax — nothing more than a joke played on an unsuspecting audience. But this hoax echoed with so many people because it appealed to a very common curiosity: what is the Moon like? Is it like the Earth? Does it host alien life? Is it real?

Our understanding of the Moon has improved dramatically since then, and we know that no goat-like creatures could live on its surface. But the Moon is still as intriguing as ever, spurring heated debates about its formation, past life forms, and even a planned human colony. A big part of these discussions, however, hinges on a particular and familiar substance: water.

Although previous research has indicated the potential of water (especially frozen water) on the lunar surface, now, for the first time, astronomers have direct evidence of ice on the satellite. Beyond the shadow of a doubt, we can now say that there’s ice on the Moon.

Using NASA’s Moon Mineralogy Mapper (M3), a team led by Shuai Li of the University of Hawaii and Brown University and including Richard Elphic from NASA’s Ames Research Center in California’s Silicon Valley, have measured how some areas of the moon absorb light. Based on that data, they’ve identified three specific signatures which together form a clear indication of ice. The signatures indicate frozen water, not liquid or vapor.

Previously, NASA’s LRO discovered that hydrogen (potentially from water) is more abundant on pole-facing slopes, a discovery consistent with the new study. Because it doesn’t have an atmosphere, the Moon is riddled with impact craters — and in the shadow of these craters, we might find the ice needed for a lunar colony. Credits: NASA.

Most of the ice is concentrated around the Moon’s darkest locations, which are consequently the coldest — the shadows of craters around the Moon’s polar areas. Because of the very small tilt of the Moon’s rotation axis, sunlight never reaches these regions, thus making the Moon unique in our solar system in terms of frozen ice.

“We found direct and definitive evidence for surface-exposed water ice in the lunar polar regions. The abundance and distribution of ice on the Moon are distinct from those on other airless bodies in the inner solar system such as Mercury and Ceres, which may be associated with the unique formation and evolution process of our Moon.”

Furthermore, researchers say, it seems like there’s enough water ice to support an exploration or even a permanent mission on the Moon. The Moon has been shown to host vast quantities of water beneath its surface, but surface ice would be much more accessible and easy to use.

It’s not the first time evidence of ice has been picked up on the moon. However, previous observations could have theoretically been explained by very reflective soils. Now, that’s out of the question.

Future research will try to explain how this ice got there in the first place and what role it plays in the lunar environment.

The study has been published in PNAS.

Illustration of the Parker Solar Probe. Credit: NASA.

NASA will soon launch a probe that will travel through the sun’s atmosphere — here’s what you need to know

Illustration of the Parker Solar Probe. Credit: NASA.

Illustration of the Parker Solar Probe. Credit: NASA.

According to Greek mythos, Daedalus was an unrivaled Athenian craftsman — the Leonardo da Vinci of his day. To his great misfortune, he angered King Minos, the ruler of the island of Crete. Desperate to flee the island, Daedalus built two pairs of wings for himself and his son Icarus, which he fixed with wax. Icarus is warned, however, that he shouldn’t fly too high lest the sun melt the wax that holds his wings. Icarus heeded his father’s advice — but only for a bit before he got cocky. Daedalus’ son flew too high and, sure enough, his wings melted, plunging the boy into the sea where he drowned.

Fast forward to present reality and the Daedaluses of our time — NASA scientists, who are gearing up for one of the most anticipated and exciting launches of the year, that of a probe destined to ‘touch’ the sun. But unlike Icarus’ flimsy, wax-coated wings, NASA’s probe is more than well equipped to brave the sun’s corona, where temperatures can reach millions of degrees Celsius.

The Parker Solar Probe ought to launch no earlier than August 6, 2018, aboard a United Launch Alliance Delta IV Heavy that will light the sky above Cape Canaveral, Florida. Today, the mission’s scientists held a press conference detailing the probe’s science goals and the technology behind it.

“We’ve been studying the Sun for decades, and now we’re finally going to go where the action is,” said Alex Young, associate director for science in the Heliophysics Science Division at NASA’s Goddard Space Flight Center in Greenbelt, Maryland.

There’s a lot of things we don’t know about the hot ball of glowing gases at the heart of our solar system. For one, the sun is dynamic, constantly belching magnetized material outward even as far as beyond Pluto’s orbit. The intensity and frequency of these ejections wax and wane according to a nearly periodical 11-year solar cycle. For instance, at the peak of the cycle, our star grows more sunspots and spews more solar flares, which can damage satellites in Earth’s orbit and even our electricity grids.

The influence of solar activity on Earth and other worlds is known as space weather. Now, scientists are looking to understand the sun and its weather activity by sending a probe in its midst, just like weather satellites in orbit that track Earth.

This mission has been in the making for the last 60 years, ever since physicist Eugene Parker published a groundbreaking scientific paper in 1958 theorizing the existence of the solar wind.

“The Sun’s energy is always flowing past our world,” said Nicky Fox, Parker Solar Probe’s project scientist at the Johns Hopkins University Applied Physics Lab. “And even though the solar wind is invisible, we can see it encircling the poles as the aurora, which are beautiful – but reveal the enormous amount of energy and particles that cascade into our atmosphere. We don’t have a strong understanding of the mechanisms that drive that wind toward us, and that’s what we’re heading out to discover.”

To undergo its mission, Parker carries a range of instruments that can study the sun both remotely and in situ (directly) — the kind of observations that might unravel some of the sun’s most well-kept secrets.

Of course, NASA has several specific questions it wants Parker to investigate. One of them has to do with the mystery of the acceleration of solar wind — the constant ejection of magnetized material from the sun. Somewhere, somehow this solar wind is accelerated to supersonic speeds.

Parker will fly straight through the corona — the sun’s atmosphere that extends millions of kilometers into outer space. The corona is scorching hot, reaching temperatures in the range of millions of degrees Celsius. However, the sun’s surface has a temperature of only about 6,000 degrees Celsius. This makes no sense at first glance: how is it possible that the surface of the sun is much less hot than its atmosphere? Well, scientists hope that Parker might come up with an answer to this counter-intuitive conundrum.

To answer these questions and more, Parker will rely on instruments such as the FIELDS suite which will capture the scale and shape of electric and magnetic fields in the Sun’s atmosphere. Of course, there will also be an imaging instrument — because how could a probe fly this close to the sun and not take awesome pictures. Called WISPR, short for Wide-Field Imager for Parker Solar Probe, the instrument is mainly designed to image coronal mass ejections (CMEs), jets and other solar ejecta. The SWEAP suite of instruments, short for Solar Wind Electrons Alphas and Protons Investigation, will count the most abundant particles in the solar wind — electrons, protons and helium ions — and measure such properties as velocity, density, and temperature to improve our understanding of the solar wind and coronal plasma. Finally,  ISʘIS suite – short for Integrated Science Investigation of the Sun, and including ʘ, the symbol for the Sun, in its acronym – measures particles across a wide range of energies in order to understand their life cycles — that is, where they came from, how they became accelerated and how they move out from the Sun through interplanetary space.

But how will Parker keep its ‘wings’ from melting? During its closest flyby, Parker will be only 6.1 million kilometers (3.8 million miles) from the sun’s surface, where temperatures can reach millions of degrees Celsius. But there’s a catch — just because the corona is that hot, that doesn’t mean that the probe will ‘feel’ that temperature due to the phenomenon of heat transfer. Simply put, some mediums conduct heat (energy) better than others.

For instance, if you stand on a bathroom’s tile floor you’ll feel cold but if you stand on a carpet your feet feel comfortably warm. However, both kinds of surfaces have the same temperature because they’ve had time to reach a thermal equilibrium — it’s just that the tile floor is a good heat conductor, which will make your feet seem cold because your body’s surface usually has a higher temperature than the ambient, whereas the carpet is a poor heat conductor and it would take you ages for your feet to match its lower temperature.

Bearing these physics in mind, we can now understand how Parker won’t get obliterated — even though the corona has a huge temperature, the sun’s outer atmosphere has a very low density and, hence, is a poor heat conductor. According to NASA, Parker’s sun-facing side will be heated to only about 1,644 degrees Kelvin (1,370 C° or 2,500 F°).

That’s still a lot, to be fair, which is why the Parker Solar Probe is equipped with a cutting-edge heat shield called the thermal protection system, or TPS. It’s a sandwich of carbon-carbon composite surrounding nearly 4.5 inches of carbon foam, which is about 97% air. Thanks to its lightweight materials, the TPS only weighs 72.5 kilograms (160 pounds) despite being nearly 2.4 meters (8 feet) in diameter. Strikingly, anything behind the shield shouldn’t heat to more than 300 Kelvin (30 C° or 85 F°)! A cooling system that runs on pressurized deionized water keep temperatures at manageable levels in the parts with Parker will be fully exposed to the sun.

The key is for the shield to be always facing the sun, but sometimes the probe will have to operate for long periods of time without being able to communicate with Earth. To solve this predicament, NASA engineers have designed a fault management system that self-corrects the probe’s course and direction facing the sun to ensure that the scientific instruments stay cool and functioning.

All in all, the Parker Solar Probe is a one-of-a-kind space mission that may not only unravel the sun’s mysteries but also those of the myriad of other stars that astronomers are eyeing.

“By studying our star, we can learn not only more about the Sun,” said Thomas Zurbuchen, the associate administrator for the Science Mission Directorate at NASA HQ. “We can also learn more about all the other stars throughout the galaxy, the universe and even life’s beginnings.”