ST/ Radio signal reveals supernova origin

Paradigm

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Paradigm

32 min readMay 19, 2023

Space biweekly vol.77, 4th May — 19th May

TL;DR

Astronomers reveal the origin of a thermonuclear supernova explosion. Strong emission lines of helium and the first detection of such a supernova in radio waves show that the exploding white dwarf star had a helium-rich companion.
Astronomers used NASA’s James Webb Space Telescope to study a rocky exoplanet known as GJ 486 b. It is too close to its star to be within the habitable zone, with a surface temperature of about 800 degrees Fahrenheit (430 degrees Celsius). And yet, their observations show hints of water vapor.
Scientists had blamed Phaethon’s comet-like behavior on dust escaping from the asteroid as it’s scorched by the Sun. However, a new study using two NASA solar observatories reveals that Phaethon’s tail is not dusty at all but is actually made of sodium gas.
For the first time, a protocluster of seven galaxies has been confirmed at a distance that astronomers refer to as redshift 7.9, or a mere 650 million years after the big bang. Based on the data collected, astronomers calculated the nascent cluster’s future development, finding that it will likely grow in size and mass to resemble the Coma Cluster, a monster of the modern universe.
It looks like a black hole and bends light like a black hole, but it could actually be a new type of star. Though the mysterious object is a hypothetical mathematical construction, new simulations by Johns Hopkins researchers suggest there could be other celestial bodies in space hiding from even the best telescopes on Earth.
An interdisciplinary team has developed an algorithm that immediately checks its own calculations of merging black holes’ properties and corrects its result if necessary — inexpensively and rapidly. The machine learning method provides very accurate information about the observed gravitational waves and will be ready for use when the global network of gravitational-wave detectors starts its next observing run.
A new study looked at a known binary star, analyzing starlight obtained from a range of ground- and space-based telescopes. The researchers found that the stars, located in a neighboring dwarf galaxy called the Small Magellanic Cloud, are in partial contact and swapping material with each other, with one star currently ‘feeding’ off the other. They orbit each other every three days and are the most massive touching stars (known as contact binaries) yet observed.
New research suggests future Martian botanists may be able to grow gene-edited rice on Mars.
Astronomers have discovered an Earth-size exoplanet, or world beyond our solar system, that may be carpeted with volcanoes. Called LP 791–18 d, the planet could undergo volcanic outbursts as often as Jupiter’s moon Io, the most volcanically active body in our solar system.
Astronomers have described the first radiation belt observed outside our solar system, using a coordinated array of 39 radio dishes from Hawaii to Germany to obtain high-resolution images. The images of persistent, intense radio emissions from an ultracool dwarf reveal the presence of a cloud of high-energy electrons trapped in the object’s powerful magnetic field, forming a double-lobed structure analogous to radio images of Jupiter’s radiation belts.
And more!

Space industry in numbers

The global smart space market size is projected to grow from USD 9.4 billion in 2020 to USD 15.3 billion by 2025, at a Compound Annual Growth Rate (CAGR) of 10.2% during the forecast period. The increasing venture capital funding and growing investments in smart space technology to drive market growth.

Analysts at Morgan Stanley and Goldman Sachs have predicted that economic activity in space will become a multi-trillion-dollar market in the coming decades. Morgan Stanley’s Space Team estimates that the roughly USD 350 billion global space industry could surge to over USD 1 trillion by 2040.

Source: Satellite Industry Association, Morgan Stanley Research, Thomson Reuters. *2040 estimates

Space industry news

Latest research

A radio-detected type Ia supernova with helium-rich circumstellar material

by Erik C. Kool, Joel Johansson, Jesper Sollerman, Jet al in Nature

Astronomers from Stockholm University reveal the origin of a thermonuclear supernova explosion. Strong emission lines of helium and the first detection of such a supernova in radio waves show that the exploding white dwarf star had a helium-rich companion.

Supernovae of Type Ia are important for astronomers since they are used to measure the expansion of the Universe. However, the origin of these explosions has remained an open question. While it is established that the explosion is that of a compact white dwarf star somehow accreting too much matter from a companion star, the exact process and the nature of the progenitor is not known. The new discovery of supernova SN 2020eyj established that the companion star was a helium star that had lost much of its material just prior to the explosion of the white dwarf.

“Once we saw the signatures of strong interaction with the material from the companion we tried to also detect it in radio emission,” explains Erik Kool, post-doc at the Department of Astronomy at Stockholm university and lead author of the paper. “The detection in radio is the first one of a Type Ia supernova — something astronomers have tried to do for decades.”

The multiband light curve of SN 2020eyj can be divided into a diffusion-peak phase and a long-lived interaction-powered tail phase.

Supernova 2020eyj was discovered by the Zwicky Transient Facility camera on Palomar mountain, where the Oskar Klein Centre at Stockholm University are members.

“The Nordic Optical telescope on La Palma was fundamental for following up this supernova,” says Professor Jesper Sollerman at the Department of Astronomy and co-author of the paper. “As were spectra from the large Keck telescope on Hawai’i that immediately revealed the very unusual helium-dominated material around the exploded star.”

Artist impression of the double star system with a compact white dwarf star accreting matter from a helium-rich donor companion. The accretion eventually leads to the white dwarf going supernova. (credit: Adam Makarenko/W. M. Keck Observatory)

“This is clearly a very unusual Type Ia supernova, but still related to the ones we use to measure the expansion of the universe,” adds Joel Johansson from the Department of Physics.
“While normal Type Ia supernovae appear to always explode with the same brightness, this supernova tells us that there are many different pathways to a white dwarf star explosion,” he adds.

High Tide or Rip-Tide on the Cosmic Shoreline? A Water-Rich Atmosphere or Stellar Contamination on GJ 486b from JWST Observations

by Moran, S.E. and Stevenson, K.B., Sing, D.K., MacDonald, R.J., et al.in Astrophysical Journal Letters

The most common stars in the universe are red dwarf stars, which means that rocky exoplanets are most likely to be found orbiting such a star. Red dwarf stars are cool, so a planet has to hug it in a tight orbit to stay warm enough to potentially host liquid water (meaning it lies in the habitable zone). Such stars are also active, particularly when they are young, releasing ultraviolet and X-ray radiation that could destroy planetary atmospheres. As a result, one important open question in astronomy is whether a rocky planet could maintain, or reestablish, an atmosphere in such a harsh environment.

To help answer that question, astronomers used NASA’s James Webb Space Telescope to study a rocky exoplanet known as GJ 486 b. It is too close to its star to be within the habitable zone, with a surface temperature of about 800 degrees Fahrenheit (430 degrees Celsius). And yet, their observations using Webb’s Near-Infrared Spectrograph (NIRSpec) show hints of water vapor. If the water vapor is associated with the planet, that would indicate that it has an atmosphere despite its scorching temperature and close proximity to its star. Water vapor has been seen on gaseous exoplanets before, but to date no atmosphere has been definitely detected around a rocky exoplanet. However, the team cautions that the water vapor could be on the star itself — specifically, in cool starspots — and not from the planet at all.

“We see a signal, and it’s almost certainly due to water. But we can’t tell yet if that water is part of the planet’s atmosphere, meaning the planet has an atmosphere, or if we’re just seeing a water signature coming from the star,” said Sarah Moran of the University of Arizona in Tucson, lead author of the study.

This graphic shows the transmission spectrum obtained by Webb observations of rocky exoplanet GJ 486 b. The science team’s analysis shows hints of water vapor; however, computer models show that the signal could be from a water-rich planetary atmosphere (indicated by the blue line) or from starspots from the red dwarf host star (indicated by the yellow line). The two models diverge noticeably at shorter infrared wavelengths, indicating that additional observations with other Webb instruments will be needed to constrain the source of the water signal.

“Water vapor in an atmosphere on a hot rocky planet would represent a major breakthrough for exoplanet science. But we must be careful and make sure that the star is not the culprit,” added Kevin Stevenson of the Johns Hopkins University Applied Physics Laboratory in Laurel, Maryland, principal investigator on the program.

GJ 486 b is about 30% larger than Earth and three times as massive, which means it is a rocky world with stronger gravity than Earth. It orbits a red dwarf star in just under 1.5 Earth days. It is expected to be tidally locked, with a permanent day side and a permanent night side. GJ 486 b transits its star, crossing in front of the star from our point of view. If it has an atmosphere, then when it transits starlight would filter through those gasses, imprinting fingerprints in the light that allow astronomers to decode its composition through a technique called transmission spectroscopy.

The team observed two transits, each lasting about an hour. They then used three different methods to analyze the resulting data. The results from all three are consistent in that they show a mostly flat spectrum with an intriguing rise at the shortest infrared wavelengths. The team ran computer models considering a number of different molecules, and concluded that the most likely source of the signal was water vapor. While the water vapor could potentially indicate the presence of an atmosphere on GJ 486 b, an equally plausible explanation is water vapor from the star. Surprisingly, even in our own Sun, water vapor can sometimes exist in sunspots because these spots are very cool compared to the surrounding surface of the star. GJ 486 b’s host star is much cooler than the Sun, so even more water vapor would concentrate within its starspots. As a result, it could create a signal that mimics a planetary atmosphere.

“We didn’t observe evidence of the planet crossing any starspots during the transits. But that doesn’t mean that there aren’t spots elsewhere on the star. And that’s exactly the physical scenario that would imprint this water signal into the data and could wind up looking like a planetary atmosphere,” explained Ryan MacDonald of the University of Michigan in Ann Arbor, one of the study’s co-authors.

A water vapor atmosphere would be expected to gradually erode due to stellar heating and irradiation. As a result, if an atmosphere is present, it would likely have to be constantly replenished by volcanoes ejecting steam from the planet’s interior. If the water is indeed in the planet’s atmosphere, additional observations are needed to narrow down how much water is present.

Future Webb observations may shed more light on this system. An upcoming Webb program will use the Mid-Infrared Instrument (MIRI) to observe the planet’s day side. If the planet has no atmosphere, or only a thin atmosphere, then the hottest part of the day side is expected to be directly under the star. However, if the hottest point is shifted, that would indicate an atmosphere that can circulate heat. Ultimately, observations at shorter infrared wavelengths by another Webb instrument, the Near-Infrared Imager and Slitless Spectrograph (NIRISS), will be needed to differentiate between the planetary atmosphere and starspot scenarios.

“It’s joining multiple instruments together that will really pin down whether or not this planet has an atmosphere,” said Stevenson.

Sodium Brightening of (3200) Phaethon near Perihelion

by Qicheng Zhang, Karl Battams, Quanzhi Ye, Matthew M. Knight, Carl A. Schmidt in The Planetary Science Journal

A weird asteroid has just gotten a little weirder. We have known for a while that asteroid 3200 Phaethon acts like a comet. It brightens and forms a tail when it’s near the Sun, and it is the source of the annual Geminid meteor shower, even though comets are responsible for most meteor showers. Scientists had blamed Phaethon’s comet-like behavior on dust escaping from the asteroid as it’s scorched by the Sun. However, a new study using two NASA solar observatories reveals that Phaethon’s tail is not dusty at all but is actually made of sodium gas.

“Our analysis shows that Phaethon’s comet-like activity cannot be explained by any kind of dust,” said California Institute of Technology PhD student Qicheng Zhang, who is the lead author of a paper.

Asteroids, which are mostly rocky, do not usually form tails when they approach the Sun. Comets, however, are a mix of ice and rock, and typically do form tails as the Sun vaporizes their ice, blasting material off their surfaces and leaving a trail along their orbits. When Earth passes through a debris trail, those cometary bits burn up in our atmosphere and produce a swarm of shooting stars — a meteor shower.

After astronomers discovered Phaethon in 1983, they realized that the asteroid’s orbit matched that of the Geminid meteors. This pointed to Phaethon as the source of the annual meteor shower, even though Phaethon was an asteroid and not a comet.

The Large Angle and Spectrometric Coronagraph (LASCO) on the Solar and Heliospheric Observatory (SOHO) imaged asteroid Phaethon through different filters as the asteroid passed near the Sun in May 2022. On the left, the sodium-sensitive orange filter shows the asteroid with a surrounding cloud and small tail, suggesting that sodium atoms from the asteroid’s surface are glowing in response to sunlight. On the right, the dust-sensitive blue filter shows no sign of Phaethon, indicating that the asteroid is not producing any detectable dust.

In 2009, NASA’s Solar Terrestrial Relations Observatory (STEREO) spotted a short tail extending from Phaethon as the asteroid reached its closest point to the Sun (or “perihelion”) along its 524-day orbit. Regular telescopes hadn’t seen the tail before because it only forms when Phaethon is too close to the Sun to observe, except with solar observatories. STEREO also saw Phaethon’s tail develop on later solar approaches in 2012 and 2016. The tail’s appearance supported the idea that dust was escaping the asteroid’s surface when heated by the Sun. However, in 2018, another solar mission imaged part of the Geminid debris trail and found a surprise. Observations from NASA’s Parker Solar Probe showed that the trail contained far more material than Phaethon could possibly shed during its close approaches to the Sun.

Zhang’s team wondered whether something else, other than dust, was behind Phaethon’s comet-like behavior. “Comets often glow brilliantly by sodium emission when very near the Sun, so we suspected sodium could likewise serve a key role in Phaethon’s brightening,” Zhang said. An earlier study, based on models and lab tests, suggested that the Sun’s intense heat during Phaethon’s close solar approaches could indeed vaporize sodium within the asteroid and drive comet-like activity.

Hoping to find out what the tail is really made of, Zhang looked for it again during Phaethon’s latest perihelion in 2022. He used the Solar and Heliospheric Observatory (SOHO) spacecraft — a joint mission between NASA and the European Space Agency (ESA) — which has color filters that can detect sodium and dust. Zhang’s team also searched archival images from STEREO and SOHO, finding the tail during 18 of Phaethon’s close solar approaches between 1997 and 2022.

In SOHO’s observations, the asteroid’s tail appeared bright in the filter that detects sodium, but it did not appear in the filter that detects dust. In addition, the shape of the tail and the way it brightened as Phaethon passed the Sun matched exactly what scientists would expect if it were made of sodium, but not if it were made of dust. This evidence indicates that Phaethon’s tail is made of sodium, not dust.

“Not only do we have a really cool result that kind of upends 14 years of thinking about a well-scrutinized object,” said team member Karl Battams of the Naval Research Laboratory, “but we also did this using data from two heliophysics spacecraft — SOHO and STEREO — that were not at all intended to study phenomena like this.”

Zhang and his colleagues now wonder whether some comets discovered by SOHO — and by citizen scientists studying SOHO images as part of the Sungrazer Project — are not comets at all.

“A lot of those other sunskirting ‘comets’ may also not be ‘comets’ in the usual, icy body sense, but may instead be rocky asteroids like Phaethon heated up by the Sun,” Zhang explained.

Still, one important question remains: If Phaethon doesn’t shed much dust, how does the asteroid supply the material for the Geminid meteor shower we see each December? Zhang’s team suspects that some sort of disruptive event a few thousand years ago — perhaps a piece of the asteroid breaking apart under the stresses of Phaethon’s rotation — caused Phaethon to eject the billion tons of material estimated to make up the Geminid debris stream. But what that event was remains a mystery.

Early Results from GLASS-JWST. XIV. A Spectroscopically Confirmed Protocluster 650 Million Years after the Big Bang

by Takahiro Morishita, Guido Roberts-Borsani, Tommaso Treu, et al in The Astrophysical Journal Letters

Every giant was once a baby, though you may never have seen them at that stage of their development. NASA’s James Webb Space Telescope has begun to shed light on formative years in the history of the universe that have thus far been beyond reach: the formation and assembly of galaxies. For the first time, a protocluster of seven galaxies has been confirmed at a distance that astronomers refer to as redshift 7.9, or a mere 650 million years after the big bang. Based on the data collected, astronomers calculated the nascent cluster’s future development, finding that it will likely grow in size and mass to resemble the Coma Cluster, a monster of the modern universe.

“This is a very special, unique site of accelerated galaxy evolution, and Webb gave us the unprecedented ability to measure the velocities of these seven galaxies and confidently confirm that they are bound together in a protocluster,” said Takahiro Morishita of IPAC-California Institute of Technology, the lead author of the study.

The precise measurements captured by Webb’s Near-Infrared Spectrograph (NIRSpec) were key to confirming the galaxies’ collective distance and the high velocities at which they are moving within a halo of dark matter — more than two million miles per hour (about one thousand kilometers per second). The spectral data allowed astronomers to model and map the future development of the gathering group, all the way to our time in the modern universe. The prediction that the protocluster will eventually resemble the Coma Cluster means that it could eventually be among the densest known galaxy collections, with thousands of members.

NIRCam red giant branch composite image of the Abell 2744 field (blue, F115W; green, F200W; red, F444W).

“We can see these distant galaxies like small drops of water in different rivers, and we can see that eventually they will all become part of one big, mighty river,” said Benedetta Vulcani of the National Institute of Astrophysics in Italy, another member of the research team.

Galaxy clusters are the greatest concentrations of mass in the known universe, which can dramatically warp the fabric of spacetime itself. This warping, called gravitational lensing, can have a magnifying effect for objects beyond the cluster, allowing astronomers to look through the cluster like a giant magnifying glass. The research team was able to utilize this effect, looking through Pandora’s Cluster to view the protocluster; even Webb’s powerful instruments need an assist from nature to see so far.

Exploring how large clusters like Pandora and Coma first came together has been difficult, due to the expansion of the universe stretching light beyond visible wavelengths into the infrared, where astronomers lacked high-resolution data before Webb. Webb’s infrared instruments were developed specifically to fill in these gaps at the beginning of the universe’s story.

The seven galaxies confirmed by Webb were first established as candidates for observation using data from the Hubble Space Telescope’s Frontier Fields program. The program dedicated Hubble time to observations using gravitational lensing, to observe very distant galaxies in detail. However, because Hubble cannot detect light beyond near-infrared, there is only so much detail it can see. Webb picked up the investigation, focusing on the galaxies scouted by Hubble and gathering detailed spectroscopic data in addition to imagery.

The research team anticipates that future collaboration between Webb and NASA’s Nancy Grace Roman Space Telescope, a high-resolution, wide-field survey mission, will yield even more results on early galaxy clusters. With 200 times Hubble’s infrared field of view in a single shot, Roman will be able to identify more protocluster galaxy candidates, which Webb can follow up to confirm with its spectroscopic instruments. The Roman mission is currently targeted for launch by May 2027.

“It is amazing the science we can now dream of doing, now that we have Webb,” said Tommaso Treu of the University of California, Los Angeles, a member of the protocluster research team. “With this small protocluster of seven galaxies, at this great distance, we had a one hundred percent spectroscopic confirmation rate, demonstrating the future potential for mapping dark matter and filling in the timeline of the universe’s early development.”

Imaging topological solitons: The microstructure behind the shadow

by Pierre Heidmann, Ibrahima Bah, and Emanuele Berti in Physical Review D

It looks like a black hole and bends light like a black hole, but it could actually be a new type of star. Though the mysterious object is a hypothetical mathematical construction, new simulations by Johns Hopkins researchers suggest there could be other celestial bodies in space hiding from even the best telescopes on Earth.

“We were very surprised,” said Pierre Heidmann, a Johns Hopkins University physicist who led the study. “The object looks identical to a black hole, but there’s light coming out from its dark spot.”

The detection of gravitational waves in 2015 rocked the world of astrophysics because it confirmed the existence of black holes. Inspired by those findings, the Johns Hopkins team set out to explore the possibility of other objects that could produce similar gravitational effects but that could be passing as black holes when observed with ultraprecise sensors on Earth, said co-author and Johns Hopkins physicist Ibrahima Bah.

“How would you tell when you don’t have a black hole? We don’t have a good way to test that,” Bah said. “Studying hypothetical objects like topological solitons will help us figure that out as well.”

Schematic description of a topological star.

The new simulations realistically depict an object the Johns Hopkins team calls a topological soliton. The simulations show an object looking like a blurry photo of a black hole from afar but like something else entirely up close. The object is hypothetical at this stage. But the fact that the team could construct it using mathematical equations and show what it looks like with simulations suggests there could be other types of celestial bodies in space hiding from even the best telescopes on Earth. The findings show how the topological soliton distorts space exactly as a black hole does — but behaves unlike a black hole as it scrambles and releases weak light rays that would not escape the strong gravitational force of a true hole.

“Light is strongly bent, but instead of being absorbed like it would in a black hole, it scatters in funky motions until at one point it comes back to you in a chaotic manner,” Heidmann said. “You don’t see a dark spot. You see a lot of blur, which means light is orbiting like crazy around this weird object.”

A black hole’s gravitational field is so intense that light can orbit around it at a certain distance from its center, in the same way that Earth orbits the sun. This distance determines the edge of the hole’s “shadow,” so that any incoming light will fatally hit the region that scientists call the “event horizon.” There, nothing can escape — not even light. The Hopkins team simulated several scenarios using pictures of outer space as if they had been captured with a camera, placing a black hole and the topological soliton in front of the lens. The results produced distorted pictures because of the gravitational effects of the massive bodies.

“These are the first simulations of astrophysically relevant string theory objects, since we can actually characterize the differences between a topological soliton and a black hole as if an observer was seeing them in the sky,” Heidmann said.

Motivated by various results from string theory, Bah and Heidmann discovered ways to construct topological solitons using Einstein’s theory of general relativity in 2021. While the solitons are not predictions of new objects, they serve as the best models of what new quantum gravity objects could look like compared to black holes. Scientists have previously created models of boson stars, gravastars, and other hypothetical objects that could exert similar gravitational effects with exotic forms of matter. But the new research accounts for pillar theories of the inner workings of the universe that other models don’t. It uses string theory that reconciles quantum mechanics and Einstein’s theory of gravity, the researchers said.

“It’s the start of a wonderful research program,” Bah said. “We hope in the future to be able to genuinely propose new types of ultracompact stars consisting of new kinds of matter from quantum gravity.”

Neural Importance Sampling for Rapid and Reliable Gravitational-Wave Inference

by Maximilian Dax, Stephen R. Green, Jonathan Gair, Michael Pürrer, Jonas Wildberger, Jakob H. Macke, Alessandra Buonanno, Bernhard Schölkopf in Physical Review Letters

When two black holes merge, they emit gravitational waves that race through space and time at the speed of light. When these reach Earth, large detectors in the United States (LIGO), Italy (Virgo) and Japan (KAGRA) can detect the signals. By comparing against theoretical predictions, scientists can then determine the black holes’ properties: masses, spins, orientation, position in the sky and distance from Earth.

A team of researchers from the Empirical Inference Department at the Max Planck Institute for Intelligent Systems (MPI-IS) in Tübingen and the Department of Astrophysical and Cosmological Relativity at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute/AEI) in Potsdam has now developed a self-checking deep learning system that very accurately extracts information from gravitational-wave data. In the process, the system checks its own predictions about the parameters of merging black holes — a deep neural network with a safety net. A set of 42 detected gravitational waves from merging black holes were successfully analyzed by the algorithm: When cross-checked against computationally expensive standard algorithms, the results were indistinguishable.

The researchers have developed a deep neural network called DINGO (Deep INference for Gravitational-wave Observations) to analyze the data. DINGO has been trained to extract — or infer — the gravitational-wave source parameters from the detector data. There was a press release on this in December 2021. The network learned to interpret real (observed) gravitational-wave data after training with many millions of simulated signals in different configurations.

Chirp mass (Mc), mass ratio (q) and sky position (α, δ) parameters for GW151012, comparing inference with DINGO and lalinference-mcmc.

However, at first glance, it is not possible to tell whether the deep neural network is reading the information correctly. Indeed, one disadvantage of common deep learning systems is that their results sound plausible even when they are wrong. That’s why the researchers at MPI-IS and AEI have added a control feature to the algorithm.

Maximilian Dax, doctoral student in the Department of Empirical Inference at MPI-IS and first author of the publication explains: “We have developed a network with a safety net. First, the algorithm calculates the properties of the black holes from the measured gravitational-wave signal. Based on these calculated parameters, a gravitational wave is modeled, and then compared to the originally observed signal. The deep neural network can thus cross-check its own results and correct them in case of doubt.”

The algorithm controls itself, making it much more reliable than previous machine learning methods. But not only that. “We were surprised to discover that the algorithm is often able to identify anomalous events, namely real data inconsistent with our theoretical models. This information can be used to quickly ‘flag’ data for additional investigation,” says Stephen Green, co-lead author, and former Senior Scientist at the AEI (now at the University of Nottingham).

“We can guarantee the accuracy of our machine learning method — which almost never happens in the field of deep learning. It therefore becomes compelling for the scientific community to use the algorithm to analyze gravitational-wave data,” says Alessandra Buonanno, author and director of the Department Astrophysical and Cosmological Relativity at the AEI. Scientists from around the world are studying gravitational waves in large collaborations, such as the LIGO Scientific Collaboration (LSC), in which more than 1,500 researchers are organized.

A low-metallicity massive contact binary undergoing slow Case A mass transfer: A detailed spectroscopic and orbital analysis of SSN 7 in NGC 346 in the SMC

by M. J. Rickard, D. Pauli in Astronomy & Astrophysics

Two massive touching stars in a neighbouring galaxy are on course to become black holes that will eventually crash together, generating waves in the fabric of space-time, according to a new study by researchers at UCL (University College London) and the University of Potsdam.

The study looked at a known binary star (two stars orbiting around a mutual centre of gravity), analysing starlight obtained from a range of ground- and space-based telescopes. The researchers found that the stars, located in a neighbouring dwarf galaxy called the Small Magellanic Cloud, are in partial contact and swapping material with each other, with one star currently “feeding” off the other. They orbit each other every three days and are the most massive touching stars (known as contact binaries) yet observed.

Comparing the results of their observations with theoretical models of binary stars’ evolution, they found that, in the best-fit model, the star that is currently being fed on will become a black hole and will feed on its companion star. The surviving star will become a black hole shortly after. These black holes will form in only a couple of million years, but will then orbit each other for billions of years before colliding with such force that they will generate gravitational waves — ripples in the fabric of space-time — that could theoretically be detected with instruments on Earth.

PhD student Matthew Rickard (UCL Physics & Astronomy), lead author of the study, said: “Thanks to gravitational wave detectors Virgo and LIGO, dozens of black hole mergers have been detected in the last few years. But so far we have yet to observe stars that are predicted to collapse into black holes of this size and merge in a time scale shorter than or even broadly comparable to the age of the universe.
“Our best-fit model suggests these stars will merge as black holes in 18 billion years. Finding stars on this evolutionary pathway so close to our Milky Way galaxy presents us with an excellent opportunity learn even more about how these black hole binaries form.”
Co-author Daniel Pauli, a PhD student at the University of Potsdam, said: “This binary star is the most massive contact binary observed so far. The smaller, brighter, hotter star, 32 times the mass of the Sun, is currently losing mass to its bigger companion, which has 55 times our Sun’s mass.”

An artist’s impression of the binary star. The smaller, brighter, hotter star (left), which is 32 times the mass of our Sun, is currently losing mass to its bigger companion (right), which has 55 times the mass of our Sun. The stars are white and blue as they are so hot: 43,000 and 38,000 degrees Kelvin respectively. Credit: UCL / J. daSilva.

The black holes that astronomers see merge today formed billions of years ago, when the universe had lower levels of iron and other heavier elements. The proportion of these heavy elements has increased as the universe has aged and this makes black hole mergers less likely. This is because stars with a higher proportion of heavier elements have stronger winds and they blow themselves apart sooner.

The well-studied Small Magellanic Cloud, about 210,000 light years from Earth, has by a quirk of nature about a seventh of the iron and other heavy metal abundances of our own Milky Way galaxy. In this respect it mimics conditions in the universe’s distant past. But unlike older, more distant galaxies, it is close enough for astronomers to measure the properties of individual and binary stars.

In their study, the researchers measured different bands of light coming from the binary star (spectroscopic analysis), using data obtained over multiple periods of time by instruments on NASA’s Hubble Space Telescope (HST) and the Multi Unit Spectroscopic Explorer (MUSE) on ESO’s Very Large Telescope in Chile, among other telescopes, in wavelengths ranging from ultraviolet to optical to near infrared. With this data, the team were able to calculate the radial velocity of the stars — that is, the movement they made towards or away from us — as well as their masses, brightness, temperature and orbits. They then matched these parameters with the best-fit evolutionary model.

Their spectroscopic analysis indicated that much of the outer envelope of the smaller star had been stripped away by its larger companion. They also observed the radius of both stars exceeded their Roche lobe — that is, the region around a star where material is gravitationally bound to that star — confirming that some of the smaller star’s material is overflowing and transferring to the companion star.

Talking through the future evolution of the stars, Rickard explained: “The smaller star will become a black hole first, in as little as 700,000 years, either through a spectacular explosion called a supernova or it may be so massive as to collapse into a black hole with no outward explosion.

“They will be uneasy neighbours for around three million years before the first black hole starts accreting mass from its companion, taking revenge on its companion.”

Pauli, who conducted the modelling work, added: “After only 200,000 years, an instant in astronomical terms, the companion star will collapse into a black hole as well. These two massive stars will continue to orbit each other, going round and round every few days for billions of years.

“Slowly they will lose this orbital energy through the emission of gravitational waves until they orbit each other every few seconds, finally merging together in 18 billion years with a huge release of energy through gravitational waves.”

Rice can grow and survive in the Martian regolith with challenges that could be overcomed through control of stress-related genes

by Peter James Icalia Gann, Abhilash Vakkada Ramachandran, Yheni Dwiningsih, Dominic Dharwadker, Vibha Srivastava in Conference: 54th Lunar Planetary Science ConferenceAt

Andy Weir’s bestselling 2011 book, The Martian, features botanist Mark Watney’s efforts to grow food on Mars after he becomes stranded there. While Watney’s initial efforts focus on growing potatoes, new research presented at the 54th Lunar and Planetary Science Conference by a team of interdisciplinary researchers from the U of A suggests future Martian botanists like Watney may have a better option: growing rice.

As outlined in the team’s abstract, Rice Can Grow and Survive in Martian Regolith with Challenges That Could be Overcome Through Control of Stress-Related Genes, one of the biggest challenges to growing food on Mars is the presence of perchlorate salts, which have been detected in the planet’s soil and are generally considered to be toxic for plants. The team was able to simulate Martian soil using basaltic rich soil mined from the Mojave Desert, called the Mojave Mars Simulant, or MMS, which was developed by scientists from NASA and the Jet Propulsion Laboratory.

The teams then grew three varieties of rice, including one wild-type and two gene-edited lines with genetic mutations that better enable them to respond to stress, such as drought, sugar starvation or salinity. These varieties were grown in the MMS, as well as a regular potted mix and a hybrid of the two. While plants were able to grow in the Martian simulant, they were not as developed as those grown in the potting soil and hybrid mix. Replacing just a quarter of the Martian simulant with potting soil resulted in improved development. The team also experimented with the amount of perchlorate in the soil, finding that 3 grams per kilogram was the threshold beyond which nothing would grow, while mutant strains could still root in 1 gram per kilogram. Their findings suggest that there might be a way forward for genetically modified rice to find purchase in Martian soil.

Next steps will include experimenting with a newer Martian soil simulant called the Mars Global Simulant, as well as other rice strains that have increased tolerance for higher salt concentrations. An important part of the research will be determining to what degree perchlorate may be leeching into the plant from the soil. Farther down the road, the researchers would like to introduce rice into a closed habitat chamber and place it in a Mars simulation chamber that replicates the temperature and atmosphere of the planet.

Whether humans ever colonize Mars, the team’s research could have applications here on Earth. Second author on the abstract, Abhilash Ramachandran, a post-doctoral fellow at the Arkansas Center for Space and Planetary Sciences, noted that he spoke with an Australian researcher from an area where the soil had high salinity, and saw their work as a potential way to grow food there. He added, “We could use Earth as a terrestrial analog before the seeds ever get sent to Mars.”

First author on the abstract, Peter James Gann, a doctoral student in cell and molecular biology, said that the project began when he met Ramachandran for coffee in the student union. “He was new here at the university, and we shared the things we were doing in our respective laboratories. Since he works on planetary science, and I specialize in cell and molecular biology, we decided to try out plants.”

They were joined by co-authors Yheni Dwiningsih, a post-doctoral associate in plant sciences; Dominic Dharwadker, an undergraduate student in the Honors College; and Vibha Srivastava, a professor in the Department of Crop, Soil and Environmental Sciences who has a joint appointment with the U of A System Division of Agriculture.

Gann, for one, is pleased with how his initial conversation with Ramachandran has turned out. “Relevant and interesting research can emanate from talking to strangers over a cup of coffee or a glass of beer,” he said, before adding: “Ain’t that cool?”

A temperate Earth-sized planet with tidal heating transiting an M6 star

by Peterson, M.S., Benneke, B., Collins, K. et al. in Nature

Astronomers have discovered an Earth-size exoplanet, or world beyond our solar system, that may be carpeted with volcanoes. Called LP 791–18 d, the planet could undergo volcanic outbursts as often as Jupiter’s moon Io, the most volcanically active body in our solar system.

They found and studied the planet using data from NASA’s TESS (Transiting Exoplanet Survey Satellite) and retired Spitzer Space Telescope, as well as a suite of ground-based observatories. A paper about the planet — led by Merrin Peterson, a graduate of the Trottier Institute for Research on Exoplanets (iREx) based at the University of Montreal.

“LP 791–18 d is tidally locked, which means the same side constantly faces its star,” said Björn Benneke, a co-author and astronomy professor at iREx who planned and supervised the study. “The day side would probably be too hot for liquid water to exist on the surface. But the amount of volcanic activity we suspect occurs all over the planet could sustain an atmosphere, which may allow water to condense on the night side.”

LP 791–18 d orbits a small red dwarf star about 90 light-years away in the southern constellation Crater. The team estimates it’s only slightly larger and more massive than Earth. Astronomers already knew about two other worlds in the system before this discovery, called LP 791–18 b and c. The inner planet b is about 20% bigger than Earth. The outer planet c is about 2.5 times Earth’s size and more than seven times its mass.

LP 791–18 d, shown here in an artist’s concept, is an Earth-size world about 90 light-years away. The gravitational tug from a more massive planet in the system, shown as a blue disk in the background, may result in internal heating and volcanic eruptions — as much as Jupiter’s moon Io, the most geologically active body in the solar system. Astronomers discovered and studied the planet using data from NASA’s Spitzer Space Telescope and TESS (Transiting Exoplanet Survey Satellite) along with many other observatories.

During each orbit, planets d and c pass very close to each other. Each close pass by the more massive planet c produces a gravitational tug on planet d, making its orbit somewhat elliptical. On this elliptical path, planet d is slightly deformed every time it goes around the star. These deformations can create enough internal friction to substantially heat the planet’s interior and produce volcanic activity at its surface. Jupiter and some of its moons affect Io in a similar way.

Planet d sits on the inner edge of the habitable zone, the traditional range of distances from a star where scientists hypothesize liquid water could exist on a planet’s surface. If the planet is as geologically active as the research team suspects, it could maintain an atmosphere. Temperatures could drop enough on the planet’s night side for water to condense on the surface.

Planet c has already been approved for observing time on the James Webb Space Telescope, and the team thinks planet d is also an exceptional candidate for atmospheric studies by the mission.

“A big question in astrobiology, the field that broadly studies the origins of life on Earth and beyond, is if tectonic or volcanic activity is necessary for life,” said co-author Jessie Christiansen, a research scientist at NASA’s Exoplanet Science Institute at the California Institute of Technology in Pasadena. “In addition to potentially providing an atmosphere, these processes could churn up materials that would otherwise sink down and get trapped in the crust, including those we think are important for life, like carbon.”

Spitzer’s observations of the system were among the last the satellite collected before it was decommissioned in January 2020.

“It is incredible to read about the continuation of discoveries and publications years beyond Spitzer’s end of mission,” said Joseph Hunt, Spitzer project manager at NASA’s Jet Propulsion Laboratory in Southern California. “That really shows the success of our first-class engineers and scientists. Together they built not only a spacecraft but also a data set that continues to be an asset for the astrophysics community.”

Resolved imaging confirms a radiation belt around an ultracool dwarf

by Melodie M. Kao, Amy J. Mioduszewski, Jackie Villadsen, Evgenya L. Shkolnik in Nature

Astronomers have described the first radiation belt observed outside our solar system, using a coordinated array of 39 radio dishes from Hawaii to Germany to obtain high-resolution images. The images of persistent, intense radio emissions from an ultracool dwarf reveal the presence of a cloud of high-energy electrons trapped in the object’s powerful magnetic field, forming a double-lobed structure analogous to radio images of Jupiter’s radiation belts.

“We are actually imaging the magnetosphere of our target by observing the radio-emitting plasma — its radiation belt — in the magnetosphere. That has never been done before for something the size of a gas giant planet outside of our solar system,” said Melodie Kao, a postdoctoral fellow at UC Santa Cruz and first author of a paper.

Strong magnetic fields form a “magnetic bubble” around a planet called a magnetosphere, which can trap and accelerate particles to near the speed of light. All the planets in our solar system that have such magnetic fields, including Earth, as well as Jupiter and the other giant planets, have radiation belts consisting of these high-energy charged particles trapped by the planet’s magnetic field.

Earth’s radiation belts, known as the Van Allen belts, are large donut-shaped zones of high-energy particles captured from solar winds by the magnetic field. Most of the particles in Jupiter’s belts are from volcanoes on its moon Io. If you could put them side by side, the radiation belt that Kao and her team have imaged would be 10 million times brighter than Jupiter’s.

Particles deflected by the magnetic field toward the poles generate auroras (“northern lights”) when they interact with the atmosphere, and Kao’s team also obtained the first image capable of differentiating between the location of an object’s aurora and its radiation belts outside our solar system.

The ultracool dwarf imaged in this study straddles the boundary between low-mass stars and massive brown dwarfs. “While the formation of stars and planets can be different, the physics inside of them can be very similar in that mushy part of the mass continuum connecting low-mass stars to brown dwarfs and gas giant planets,” Kao explained.

Characterizing the strength and shape of the magnetic fields of this class of objects is largely uncharted terrain, she said. Using their theoretical understanding of these systems and numerical models, planetary scientists can predict the strength and shape of a planet’s magnetic field, but they haven’t had a good way to easily test those predictions.

“Auroras can be used to measure the strength of the magnetic field, but not the shape. We designed this experiment to showcase a method for assessing the shapes of magnetic fields on brown dwarfs and eventually exoplanets,” Kao said.

The strength and shape of the magnetic field can be an important factor in determining a planet’s habitability.

“When we’re thinking about the habitability of exoplanets, the role of their magnetic fields in maintaining a stable environment is something to consider in addition to things like the atmosphere and climate,” Kao said.

To generate a magnetic field, a planet’s interior must be hot enough to have electrically conducting fluids, which in the case of Earth is the molten iron in its core. In Jupiter, the conducting fluid is hydrogen under so much pressure it becomes metallic. Metallic hydrogen probably also generates magnetic fields in brown dwarfs, Kao said, while in the interiors of stars the conducting fluid is ionized hydrogen.

The ultracool dwarf known as LSR J1835+3259 was the only object Kao felt confident would yield the high-quality data needed to resolve its radiation belts. “Now that we’ve established that this particular kind of steady-state, low-level radio emission traces radiation belts in the large-scale magnetic fields of these objects, when we see that kind of emission from brown dwarfs — and eventually from gas giant exoplanets — we can more confidently say they probably have a big magnetic field, even if our telescope isn’t big enough to see the shape of it,” Kao said, adding that she is looking forward to when the Next Generation Very Large Array, currently being planned by the National Radio Astronomy Observatory (NRAO), can image many more extrasolar radiation belts.

“This is a critical first step in finding many more such objects and honing our skills to search for smaller and smaller magnetospheres, eventually enabling us to study those of potentially habitable, Earth-size planets,” said coauthor Evgenya Shkolnik at Arizona State University, who has been studying the magnetic fields and habitability of planets for many years.

The team used the High Sensitivity Array, consisting of 39 radio dishes coordinated by the NRAO in the United States and the Effelsberg radio telescope operated by the Max Planck Institute for Radio Astronomy in Germany.

“By combining radio dishes from across the world, we can make incredibly high-resolution images to see things no one has ever seen before. Our image is comparable to reading the top row of an eye chart in California while standing in Washington, D.C.,” said coauthor Jackie Villadsen at Bucknell University.