ST/ CHEOPS detects a ‘rainbow’ on an exoplanet

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Paradigm

29 min readApr 11, 2024

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Space biweekly vol.95, 28th March — 11th April

TL;DR

CHEOPS space telescope sheds light on WASP-76b, revealing an asymmetry between its eastern and western terminators, possibly due to a luminous phenomenon akin to a rainbow called a ‘glory’.
ALMA radio telescope identifies over 100 molecular species in a highly active star-forming galaxy, surpassing previous findings and opening avenues for studying other galaxies.
High sensitivity radio observations uncover a magnetized plasma cloud in the Hydra galaxy cluster, dubbed the Flying Fox, challenging conventional explanations.
NASA’s James Webb Space Telescope surveys starburst galaxy M82, showcasing its intense star formation activity surpassing that of the Milky Way.
Moon’s gravity field analysis combined with evolutionary models suggests it turned inside out after solidifying, leaving behind titanium-rich material causing gravity anomalies.
Simulations explore collisions of densely packed stars at the Milky Way’s center, revealing outcomes ranging from ‘violent high fives’ to mergers.
Rare dust particle from an extraterrestrial meteorite formed by a foreign star is discovered.
Images capture turbulence development as a Coronal Mass Ejection interacts with solar wind in the circumsolar space.
Smallest ‘starquakes’ ever recorded are detected in an orange dwarf star by an international team of scientists.
Astronomers measure the speed of fast-moving jets from ‘cosmic cannibal’ stars, crucial for understanding star formation and elemental distribution, using a groundbreaking experiment.
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

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Asymmetry in the atmosphere of the ultra-hot Jupiter WASP-76 b

by O. D. S. Demangeon, P. E. Cubillos, V. Singh, T. G. Wilson, L. Carone, et al in Astronomy & Astrophysics

The CHEOPS space telescope, whose scientific operations centre is based at the University of Geneva (UNIGE), is providing new information on the mysterious exoplanet WASP-76b. This ultra-hot giant is characterised by an asymmetry between the amount of light observed on its eastern terminator — the fictitious line that separates its night side from its day side — and that observed on its western terminator. This peculiarity is thought to be due to a ‘’glory’’, a luminous phenomenon similar to a rainbow, which occurs if the light from the star — the ‘’sun’’ around which the exoplanet orbits — is reflected by clouds made up of a perfectly uniform substance. If this hypothesis is confirmed, this would be the first detection of this phenomenon outside our solar system. This work is carried out in collaboration with the European Space Agency (ESA) and the University of Bern (UNIBE).

WASP-76b is an ultra-hot giant planet. Orbiting its host star twelve times closer than Mercury orbits our Sun, it receives more than 4,000 times the Sun’s radiation on Earth. ‘’The exoplanet is ‘inflated’ by the intense radiation from its star. So, although it is 10% less massive than our cousin Jupiter, it is almost twice as big,’’ explains Monika Lendl, assistant professor in the Department of Astronomy of the UNIGE Faculty of Science, and co-author of the study.

Since its discovery in 2013, WASP-76b has been the subject of intense scrutiny by astronomers. A strangely hellish picture has emerged. One side of the planet is always facing its star, reaching temperatures of 2,400 degrees Celsius. Elements that would form rocks on Earth melt and evaporate here, before condensing on the slightly cooler night side, creating clouds of iron that drip molten iron rain.

One of the most disturbing observations for astronomers is the asymmetry between the planet’s two terminators. The terminator is the imaginary line that separates the day and night sides of a planet. In the case of WASP-76b, the observations show an increase in the amount of light from the terminator to the east of the planet compared with the one to the west. To solve this mystery, astronomers used no fewer than twenty-three observations with the CHEOPS space telescope, spread over three years. The ESA satellite, which is piloted by Switzerland and has its scientific operations centre at the UNIGE Department of Astronomy, observed numerous secondary eclipses of the planet (when it passes behind its star) and several phase curves (continuous observation during a complete revolution of the planet).

Reduced and phase-folded light-curves in CHEOPS, TESS, *Spitzer*-IRAC1 and *Spitzer*-IRAC2 bandpasses: The light-curves are corrected from the contamination and from modelled instrumental systematic. The zero flux level is set as the stellar flux, except for the Spitzer-IRAC1 data where, in the absence of a reliable PC, we set the out-of-transit and the out-of-eclipse flux level to zero.

Combining these new data with those from other telescopes (TESS, Hubble and Spitzer), the astronomers were able to put forward a surprising hypothesis to explain the excess luminous flux on the eastern side of the planet: ‘’This unexpected glow could be caused by a strong, localised and anisotropic reflection — i.e. one that depends on direction — what we call a glory,’’ explains Olivier Demangeon, researcher at the Instituto de Astrofísica e Ciências do Espaço in Portugal and lead author of the study.

Glories are common phenomena on Earth. They have also been observed on Venus. The effect, similar to a rainbow, occurs when light is reflected by clouds made up of perfectly uniform droplets. In the case of Earth, the droplets are made out of water, but the nature of these droplets on WASP-76b remains mysterious. It could be iron, as this has already been detected in the planet’s extremely hot atmosphere. The detection of this phenomenon on WASP-76b is the first of its kind outside our solar system.

Reduced and phase-folded light-curves in CHEOPS and TESS bandpasses using the Cos+Kelp,Refl phase curve models.

‘’The reason why no such glory has ever been observed outside our solar system is that this phenomenon requires very specific conditions. First of all, the atmospheric particles must be almost perfectly spherical, completely uniform and sufficiently stable to be observed throughout a long time. These droplets have to be directly illuminated by the planet’s host star, and the observer — in this case CHEOPS — must be in the right position,’’ explains Olivier Demangeon.

Further data will be needed to confirm with certainty that this intriguing excess of light on the eastern terminator of WASP-76b is a glory. This confirmation would attest to the presence of clouds made up of perfectly spherical droplets that have existed for at least three years, or that are constantly renewing themselves. For such clouds to persist, the temperature of the atmosphere would also have to be stable over time — a fascinating and detailed insight into what could be happening on WASP-76b.

Detecting such tiny phenomena at such a great distance will enable scientists and engineers to identify others that are just as crucial. For example, the reflection of starlight off liquid lakes and oceans — a necessary condition for habitability.

The ALCHEMI Atlas: Principal Component Analysis Reveals Starburst Evolution in NGC 253

by Nanase Harada, David S. Meier, Sergio Martín, et al in The Astrophysical Journal Supplement Series

The ALMA radio telescope has detected more than 100 molecular species, including many indicative of different star formation and evolution processes, in a galaxy where stars are forming much more actively than in the Milky Way. This is far more molecules than were found in previous studies. Now the team will try to apply this knowledge to other galaxies.

A team of researchers led by Sergio Martin of the European Southern Observatory/Joint ALMA Observatory, Nanase Harada of the National Astronomical Observatory of Japan, and Jeff Mangum of the National Radio Astronomy Observatory used ALMA (Atacama Large Millimeter/submillimeter Array) to observe the center of a galaxy known as NGC 253. NGC 253 is located about 10 million light-years away in the direction of the constellation Sculptor. NGC 253 is an example of a starburst galaxy, a galaxy where many new stars are forming rapidly. The factors leading to the onset of a starburst are still not well understood.

Top: Velocity-integrated images of CO(1–0) in blue, H39α in red, and CH3OH(2K –1K ) around the rest frequency of 96.7 GHz in green. Rough positions of parts of the x1 orbits and the full x2 orbits farther inside are shown with dashed–dotted and dashed lines, respectively. Note that these are just some examples of the presumably large families of possible x1 and x2 orbits. There likely exists another x2 orbit connecting GMCs 3–6 or 3–7 (see Levy et al. 2022) almost fully edge-on. The synthetic beam size is shown at the left bottom corner as a white circle. Bottom: The same as the top panel, but with HC3N(25–24) in red, and CN(3–2) in green. Intensities are scaled so that faint lines have similar dynamic ranges as other lines.

The birth, evolution, and death of stars change the molecular composition of the surrounding gas. ALMA’s high sensitivity and high resolution allowed astronomers to determine the locations of molecules indicative of the various stages in the life cycle of stars. This survey, dubbed ALCHEMI (ALMA Comprehensive High-resolution Extragalactic Molecular Inventory), found high-density molecular gas that is likely promoting active star formation in this galaxy. The amount of dense gas in the center of NGC 253 turned out to be more than 10 times higher than that in the center of the Milky Way, which could explain why NGC 253 is forming stars about 30 times more efficiently.

The ALCHEMI survey also provided an atlas of 44 molecular species, doubling the number available from previous studies outside the Milky Way. By applying a machine-learning technique to this atlas, the researchers were able to identify which molecules serve as the best signposts to trace the story of star formation from the beginning to the end. This knowledge will help in planning future ALMA observations.

Discovery of diffuse radio source in Abell 1060

by Kohei Kurahara, Takuya Akahori, Aika Oki, Yuki Omiya, Kazuhiro Nakazawa in Publications of the Astronomical Society of Japan

High sensitivity radio observations have discovered a cloud of magnetized plasma in the Hydra galaxy cluster. The odd location and shape of this plasma defy all conventional explanations. Dubbed the Flying Fox based on its silhouette, this plasma will remain a mystery until additional observations can provide more insight.

A team led by Kohei Kurahara at the National Astronomical Observatory of Japan analyzed observations from the Giant Metrewave Radio Telescope (GMRT) targeting the Hydra galaxy cluster, located over 100 million light years away in the direction of the constellation Hyrda. By applying recent analysis techniques to the GMRT (Giant Metrewave Radio Telescope) data archive, the team was able to discover a cloud of magnetized plasma shaped like a flying fox which has never been reported before.

GMRT radio image of the central region of the Hydra Cluster. The “head” of the Flying Fox discovered this time points to the south-west (lower right). The Flying Fox has a “wingspan” of 220,000 light years. The white contours in the background show the X-ray surface brightness as observed by ESA’s XMM-Newton satellite.(Credit: Kohei Kurahara)

Radio/optical/IR/X-ray images failed to find a host galaxy at the center of the Flying Fox. This combined with its elongated shape, has left astronomers scratching their heads; the Flying Fox does not fit the model for any known class of objects. New observing facilities, like the Square Kilometre Array currently under construction, are expected to study the Flying Fox and provide new insights into the nature and history of this unusual object.

JWST Observations of Starbursts: Polycyclic Aromatic Hydrocarbon Emission at the Base of the M 82 Galactic Wind

by Alberto D. Bolatto, Rebecca C. Levy, Elizabeth Tarantino, Martha L. Boyer, et al in The Astrophysical Journal

A team of astronomers has used NASA’s James Webb Space Telescope to survey the starburst galaxy Messier 82 (M82). Located 12 million light-years away in the constellation Ursa Major, this galaxy is relatively compact in size but hosts a frenzy of star formation activity. For comparison, M82 is sprouting new stars 10 times faster than the Milky Way galaxy.

Led by Alberto Bolatto at the University of Maryland, College Park, the team directed Webb’s NIRCam (Near-Infrared Camera) instrument toward the starburst galaxy’s center, attaining a closer look at the physical conditions that foster the formation of new stars.

“M82 has garnered a variety of observations over the years because it can be considered as the prototypical starburst galaxy,” said Bolatto, lead author of the study. “Both NASA’s Spitzer and Hubble space telescopes have observed this target. With Webb’s size and resolution, we can look at this star-forming galaxy and see all of this beautiful, new detail.”

Star formation continues to maintain a sense of mystery because it is shrouded by curtains of dust and gas, creating an obstacle in observing this process. Fortunately, Webb’s ability to peer in the infrared is an asset in navigating these murky conditions. Additionally, these NIRCam images of the very center of the starburst were obtained using an instrument mode that prevented the very bright source from overwhelming the detector.

While dark brown tendrils of heavy dust are threaded throughout M82’s glowing white core even in this infrared view, Webb’s NIRCam has revealed a level of detail that has historically been obscured. Looking closer toward the center, small specks depicted in green denote concentrated areas of iron, most of which are supernova remnants. Small patches that appear red signify regions where molecular hydrogen is being lit up by a nearby young star’s radiation.

“This image shows the power of Webb,” said Rebecca Levy, second author of the study at the University of Arizona, Tucson. “Every single white dot in this image is either a star or a star cluster. We can start to distinguish all of these tiny point sources, which enables us to acquire an accurate count of all the star clusters in this galaxy.”

On the left is the starburst galaxy M82 as observed by NASA’s Hubble Space Telescope in 2006. The small box at the galaxy’s core corresponds to the area captured so far by the NIRCam (Near-Infrared Camera) instrument on NASA’s James Webb Space Telescope. The red filaments as seen by Webb are the polycyclic aromatic hydrocarbon emission, which traces the shape of the galactic wind. In the Hubble image, light at .814 microns is colored red, .658 microns is red-orange, .555 microns is green, and .435 microns is blue (filters F814W, F658N, F555W, and F435W, respectively). In the Webb image, light at 3.35 microns is colored red, 2.50 microns is green, and 1.64 microns is blue (filters F335M, F250M, and F164N, respectively). NASA, ESA, CSA, STScI, A. Bolatto (University of Maryland)

Looking at M82 in slightly longer infrared wavelengths, clumpy tendrils represented in red can be seen extending above and below the galaxy’s plane. These gaseous streamers are a galactic wind rushing out from the core of the starburst. One area of focus for this research team was understanding how this galactic wind, which is caused by the rapid rate of star formation and subsequent supernovae, is being launched and influencing its surrounding environment. By resolving a central section of M82, scientists could examine where the wind originates, and gain insight on how hot and cold components interact within the wind.

Webb’s NIRCam instrument was well-suited to trace the structure of the galactic wind via emission from sooty chemical molecules known as polycyclic aromatic hydrocarbons (PAHs). PAHs can be considered as very small dust grains that survive in cooler temperatures but are destroyed in hot conditions.

Much to the team’s surprise, Webb’s view of the PAH emission highlights the galactic wind’s fine structure — an aspect previously unknown. Depicted as red filaments, the emission extends away from the central region where the heart of star formation is located. Another unanticipated find was the similar structure between the PAH emission and that of hot, ionized gas.

“It was unexpected to see the PAH emission resemble ionized gas,” said Bolatto. “PAHs are not supposed to live very long when exposed to such a strong radiation field, so perhaps they are being replenished all the time. It challenges our theories and shows us that further investigation is required.”

Webb’s observations of M82 in near-infrared light spur further questions about star formation, some of which the team hopes to answer with additional data gathered with Webb, including that of another starburst galaxy. Two other papers from this team characterizing the stellar clusters and correlations among wind components of M82 are almost finalized.

In the near future, the team will have spectroscopic observations of M82 from Webb ready for their analysis, as well as complementary large-scale images of the galaxy and wind. Spectral data will help astronomers determine accurate ages for the star clusters and provide a sense of timing for how long each phase of star formation lasts in a starburst galaxy environment. On a broader scale, inspecting the activity in galaxies like M82 can deepen astronomers’ understanding of the early universe.

“Webb’s observation of M82, a target closer to us, is a reminder that the telescope excels at studying galaxies at all distances,” said Bolatto. “In addition to looking at young, high-redshift galaxies, we can look at targets closer to home to gather insight into the processes that are happening here — events that also occurred in the early universe.”

Vestiges of a lunar ilmenite layer following mantle overturn revealed by gravity data

by Weigang Liang, Adrien Broquet, Jeffrey C. Andrews-Hanna, Nan Zhang, Min Ding, Alexander J. Evans in Nature Geoscience

About 4.5 billion years ago, a small planet smashed into the young Earth, flinging molten rock into space. Slowly, the debris coalesced, cooled and solidified, forming our moon. This scenario of how the Earth’s moon came to be is the one largely agreed upon by most scientists. But the details of how exactly that happened are “more of a choose-your-own adventure novel,” according to researchers in the University of Arizona Lunar and Planetary Laboratory who published a paper. The findings offer important insights into the evolution of the lunar interior, and potentially for planets such as the Earth or Mars.

Most of what is known about the origin of the moon comes from analyses of rock samples, collected by Apollo astronauts more than 50 years ago, combined with theoretical models. The samples of basaltic lava rocks brought back from the moon showed surprisingly high concentrations of titanium. Later satellite observations found that these titanium-rich volcanic rocks are primarily located on the moon’s nearside, but how and why they got there has remained a mystery — until now.

Because the moon formed fast and hot, it was likely covered by a global magma ocean. As the molten rock gradually cooled and solidified, it formed the moon’s mantle and the bright crust we see when we look up at a full moon at night. But deeper below the surface, the young moon was wildly out of equilibrium. Models suggest that the last dregs of the magma ocean crystallized into dense minerals including ilmenite, a mineral containing titanium and iron.

“Because these heavy minerals are denser than the mantle underneath, it creates a gravitational instability, and you would expect this layer to sink deeper into the moon’s interior,” said Weigang Liang, who led the research as part of his doctoral work at LPL.

Somehow, in the millennia that followed, that dense material did sink into the interior, mixed with the mantle, melted and returned to the surface as titanium-rich lava flows that we see on the surface today.

“Our moon literally turned itself inside out,” said co-author and LPL associate professor Jeff Andrews-Hanna. “But there has been little physical evidence to shed light on the exact sequence of events during this critical phase of lunar history, and there is a lot of disagreement in the details of what went down — literally.”

Bouguer gravity gradients over the nearside mare region.

Did this material sink as it formed a little at a time, or all at once after the moon had fully solidified? Did it sink into the interior globally and then rise up on the near side, or did it migrate to the near side and then sink? Did it sink in one big blob, or several smaller blobs?

“Without evidence, you can pick your favorite model. Each model holds profound implications for the geologic evolution of our moon,” said co-lead author Adrien Broquet of the German Aerospace Center in Berlin, who did the work during his time as a postdoctoral research associate at LPL.

In a previous study, led by Nan Zhang at Peking University in Beijing, who is also a co-author on the latest paper, models predicted that the dense layer of titanium-rich material beneath the crust first migrated to the near side of the moon, possibly triggered by a giant impact on the far side, and then sunk into the interior in a network of sheetlike slabs, cascading into the lunar interior almost like waterfalls. But when that material sank, it left behind a small remnant in a geometric pattern of intersecting linear bodies of dense titanium-rich material beneath the crust.

“When we saw those model predictions, it was like a lightbulb went on,” said Andrews-Hanna, “because we see the exact same pattern when we look at subtle variations in the moon’s gravity field, revealing a network of dense material lurking below the crust.”

In the new study, the authors compared simulations of a sinking ilmenite-rich layer to a set of linear gravity anomalies detected by NASA’s GRAIL mission, whose two spacecraft orbited the moon between 2011 and 2012, measuring tiny variations in its gravitational pull. These linear anomalies surround a vast dark region of the lunar near side covered by volcanic flows known as mare (Latin for “sea”). The authors found that the gravity signatures measured by the GRAIL mission are consistent with ilmenite layer simulations, and that the gravity field can be used to map out the distribution of the ilmenite remnants left after the sinking of the majority of the dense layer.

“Our analyses show that the models and data are telling one remarkably consistent story,” Liang said. “Ilmenite materials migrated to the near side and sunk into the interior in sheetlike cascades, leaving behind a vestige that causes anomalies in the moon’s gravity field, as seen by GRAIL.”

The team’s observations also constrain the timing of this event: The linear gravity anomalies are interrupted by the largest and oldest impact basins on the near side and therefore must have formed earlier. Based on these cross-cutting relationships, the authors suggest that the ilmenite-rich layer sank prior to 4.22 billion years ago, which is consistent with it contributing to later volcanism seen on the lunar surface.

“Analyzing these variations in the moon’s gravity field allowed us to peek under the moon’s surface and see what lies beneath,” said Broquet, who worked with Liang to show that the anomalies in the moon’s gravitational field match what would be expected for the zones of dense titanium-rich material predicted by computer simulation models of lunar overturn. While the detection of lunar gravity anomalies provides evidence for the sinking of a dense layer in the moon’s interior and allows for a more precise estimate of how and when this event occurred, what we see on the surface of the moon adds even more intrigue to the story, according to the research team.

“The moon is fundamentally lopsided in every respect,” Andrews-Hanna said, explaining that the near side facing the Earth, and particularly the dark region known as Oceanus Procellarum region, is lower in elevation, has a thinner crust, is largely covered in lava flows, and has high concentrations of typically rare elements like titanium and thorium. The far side differs in each of these respects. Somehow, the overturn of the lunar mantle is thought to be related to the unique structure and history of the near side Procellarum region. But the details of that overturn have been a matter of considerable debate among scientists.

“Our work connects the dots between the geophysical evidence for the interior structure of the moon and computer models of its evolution,” Liang added.
“For the first time we have physical evidence showing us what was happening in the moon’s interior during this critical stage in its evolution, and that’s really exciting,” Andrews-Hanna said. “It turns out that the moon’s earliest history is written below the surface, and it just took the right combination of models and data to unveil that story.”

Collisional Shaping of Nuclear Star Cluster Density Profiles

by Sanaea C. Rose, Morgan MacLeod in arXiv

Despite their ancient ages, some stars orbiting the Milky Way’s central supermassive black hole appear deceptively youthful. But unlike humans, who might appear rejuvenated from a fresh round of collagen injections, these stars look young for a much darker reason. They ate their neighbors.

This is just one of the more peculiar findings from new Northwestern University research. Using a new model, astrophysicists traced the violent journeys of 1,000 simulated stars orbiting our galaxy’s central supermassive black hole, Sagittarius A* (Sgr A*).

So densely packed with stars, the region commonly experiences brutal stellar collisions. By simulating the effects of these intense collisions, the new work finds that collision survivors can lose mass to become stripped down, low-mass stars or can merge with other stars to become massive and rejuvenated in appearance.

“The region around the central black hole is dense with stars moving at extremely high speeds,” said Northwestern’s Sanaea C. Rose, who led the research. “It’s a bit like running through an incredibly crowded subway station in New York City during rush hour. If you aren’t colliding into other people, then you are passing very closely by them. For stars, these near collisions still cause them to interact gravitationally. We wanted to explore what these collisions and interactions mean for the stellar population and characterize their outcomes.”

Illustration of stars orbiting close to the Milky Way’s central supermassive black hole. Credit: ESO/L. Calçada/Spaceengine.org

Rose is the Lindheimer Postdoctoral Fellow at Northwestern’s Center for Interdisciplinary Exploration and Research in Astrophysics (CIERA). She began this work as a Ph.D. candidate at UCLA. The center of our Milky Way is a strange and wild place. The gravitational pull of Sgr A* accelerates stars to whip around their orbits at terrifying speeds. And the sheer number of stars packed into the galaxy’s center is upwards of a million. The densely packed cluster plus the lightning-fast speeds equal a high-speed demolition derby. In the innermost region — within 0.1 parsecs of the black hole — few stars escape unscathed.

“The closest star to our sun is about four light-years away,” Rose explained. “Within that same distance near the supermassive black hole, there are more than a million stars. It’s an incredibly crowded neighborhood. On top of that, the supermassive black hole has a really strong gravitational pull. As they orbit the black hole, stars can move at thousands of kilometers per second.”

Within this tight, hectic neighborhood, stars can collide with other stars. And the closer stars live to the supermassive black hole, the likelihood of collision increases. Curious of the outcomes of these collisions, Rose and her collaborators developed a simulation to trace the fates of stellar populations in the galactic center. The simulation takes several factors into account: density of the stellar cluster, mass of the stars, orbit speed, gravity and distances from the Sgr A*.

In her research, Rose pinpointed one factor that is most likely to determine a star’s fate: its distance from the supermassive black hole. Within 0.01 parsecs from the black hole, stars — moving at speeds reaching thousands of kilometers per second — constantly bump into one another. It’s rarely a head-on collision and more like a “violent high five,” as Rose describes it. The impacts are not strong enough to smash the stars completely. Instead, they shed their outer layers and continue speeding along the collision course.

“They whack into each other and keep going,” Rose said. “They just graze each other as though they are exchanging a very violent high five. This causes the stars to eject some material and lose their outer layers. Depending on how fast they are moving and how much they overlap when they collide, they might lose quite a bit of their outer layers. These destructive collisions result in a population of strange, stripped down, low-mass stars.”

Outside of 0.01 parsecs, stars move at a more relaxed pace — hundreds of kilometers per second as opposed to thousands. Because of the slower speeds, these stars collide with one another but then don’t have enough energy to escape. Instead, they merge to become more massive. In some cases, they might even merge multiple times to become 10 times more massive than our sun.

“A few stars win the collision lottery,” Rose said. “Through collisions and mergers, these stars collect more hydrogen. Although they were formed from an older population, they masquerade as rejuvenated, young-looking stars. They are like zombie stars; they eat their neighbors.” But the youthful appearance comes at the cost of a shorter life expectancy.
“They die very quickly,” Rose said. “Massive stars are sort of like giant, gas-guzzling cars. They start with a lot of hydrogen, but they burn through it very, very fast.”

Although Rose finds simple joy in studying the bizarre, extreme region near our galactic center, her work also can reveal information about the history of the Milky Way. And because the central cluster is extremely difficult to observe, her team’s simulations can illuminate otherwise hidden processes.

“It’s an environment unlike any other,” Rose said. “Stars, which are under the influence of a supermassive black hole in a very crowded region, are unlike anything we will ever see in our own solar neighborhood. But if we can learn about these stellar populations, then we might be able to learn something new about how the galactic center was assembled. At the very least, it certainly provides a point of contrast for the neighborhood where we live.”

Atomic-scale Element and Isotopic Investigation of 25Mg-rich Stardust from an H-burning Supernova

by N. D. Nevill, P. A. Bland, D. W. Saxey, W. D. A. Rickard, P. Guagliardo, N. E. Timms, L. V. Forman, L. Daly, S. M. Reddy in The Astrophysical Journal

Curtin University-led research has discovered a rare dust particle trapped in an ancient extra-terrestrial meteorite that was formed by a star other than our sun.

The discovery was made by lead author Dr Nicole Nevill and colleagues during her PhD studies at Curtin, now working at the Lunar and Planetary Science Institute in collaboration with NASA’s Johnson Space Centre. Meteorites are mostly made up of material that formed in our solar system and can also contain tiny particles which originate from stars born long before our sun.

Clues that these particles, known as presolar grains, are relics from other stars are found by analysing the different types of elements inside them. Dr Nevill used a technique called atom probe tomography to analyse the particle and reconstruct the chemistry on an atomic scale, accessing the hidden information within.

“These particles are like celestial time capsules, providing a snapshot into the life of their parent star,” Dr Nevill said. “Material created in our solar system have predictable ratios of isotopes — variants of elements with different numbers of neutrons. The particle that we analysed has a ratio of magnesium isotopes that is distinct from anything in our solar system.
“The results were literally off the charts. The most extreme magnesium isotopic ratio from previous studies of presolar grains was about 1,200. The grain in our study has a value of 3,025, which is the highest ever discovered. “This exceptionally high isotopic ratio can only be explained by formation in a recently discovered type of star — a hydrogen burning supernova.”

Presolar oxygen and silicon isotopic compositions of N-AL6 determined using NanoSIMS, shown against O and Si isotopic values of presolar grains measured in previous studies and extracted from the Washington University Presolar Grain Database (Hynes & Gyngard 2009).

Co-author Dr David Saxey, from the John de Laeter Centre at Curtin said the research is breaking new ground in how we understand the universe, pushing the boundaries of both analytical techniques and astrophysical models.

“The atom probe has given us a whole level of detail that we haven’t been able to access in previous studies,” Dr Saxey said. “Hydrogen burning supernova is a type of star that has only been discovered recently, around the same time as we were analysing the tiny dust particle. The use of the atom probe in this study, gives a new level of detail helping us understand how these stars formed.”

Co-author Professor Phil Bland, from Curtin’s School of Earth and Planetary Sciences said new discoveries from studying rare particles in meteorites are enabling us to gain insights into cosmic events beyond our solar system.

“It is simply amazing to be able to link atomic-scale measurements in the lab to a recently discovered type of star.”

First Direct Imaging of a Kelvin–Helmholtz Instability by PSP/WISPR

by Evangelos Paouris, Guillermo Stenborg, Mark G. Linton, Angelos Vourlidas, Russell A. Howard, Nour E. Raouafi in The Astrophysical Journal

The Wide-field Imager for Parker Solar Probe (WISPR) Science Team, led by the U.S. Naval Research Laboratory (NRL), captured the development of turbulence as a Coronal Mass Ejection (CME) interacted with the ambient solar wind in the circumsolar space.

Taking advantage of its unique location inside the Sun’s atmosphere, the NRL-built WISPR telescope on NASA’s Parker Solar Probe (PSP) mission, operated by the Johns Hopkins University Applied Physics Laboratory (JHUAPL), captured in unparalleled detail the interaction between a CME and the background ambient solar wind. To the surprise of the WISPR team, images from one of the telescopes showed what seemed like turbulent eddies, so-called Kelvin-Helmholtz instabilities (KHI). Such structures have been imaged in the terrestrial atmosphere as trains of crescent wave-like clouds and are the results of strong wind shear between the upper and lower levels of the cloud. This phenomenon, while rarely imaged, is thought to occur regularly at the interface of fluid flows when the right conditions arise.

“We never anticipated that KHI structures could develop to large enough scales to be imaged in visible light CME images in the heliosphere when we designed the instrument,” said Angelos Vourlidas, Ph.D., JHUAPL and WISPR Project Scientist. “These fine detail observations show the power of the WISPR high sensitivity detector combined with the close-up vantage point afforded by Parker Solar Probe’s unique sun-encounter orbit,” said Mark Linton, Ph.D., head, NRL Heliophysics Theory and Modeling Section and Principal Investigator for the WISPR instrument.

The CME on 2021 November 20 at 00:03:20 UT and 02:18:20 UT as observed by WISPR-I. The asterisks mark the two features (Feature A in yellow and Feature B in cyan) used to characterize the CME kinematics. The yellow, rectangular box points out the region where the plausible signatures of a KHI were observed.

The KHI structures were detected by the keen eye of an early career member of the WISPR team, Evangelos Paouris, Ph.D., George Mason University. Paouris, and his WISPR colleagues, undertook a thorough investigation to verify that the structures were indeed KHI waves. The results not only report an extremely rare phenomenon, even at Earth, but also open a new window of investigation with important consequences for the civilian and Department of Defense (DOD) communities.

“The turbulence that gives rise to KHI plays a fundamental role in regulating the dynamics of CMEs flowing through the ambient solar wind. Hence, understanding turbulence is key in achieving a deeper understanding of CME evolution and kinematics,” said Paouris. By extension, this knowledge will lead to more accurate forecasting of the arrival of CMEs in Earth’s vicinity and their effects on civilian and DOD space assets, thus safeguarding society and the warfighter.

“The direct imaging of extraordinary ephemeral phenomena like KHI with WISPR/PSP is a discovery that opens a new window to better understand CME propagation and their interaction with the ambient solar wind,” Paouris said.

WISPR is the only imaging instrument aboard the NASA Parker Solar Probe mission. The instrument, designed, developed and led by NRL, records visible-light images of the solar corona and solar outflow in two overlapping cameras that together observe more than 100-degrees angular width from the Sun. This NASA mission travels closer to the Sun than any other mission. PSP uses a series of Venus flyby’s to gradually reduce its perihelion from 36 solar radii in 2018 to 9.5 in 2025. The mission is approaching its 19th perihelion on March 30, 2024 at a distance of 11.5 solar radii from Sun center.

By observing the data the team found the Kelvin-Helmholtz instability is excited at the boundary between the CME and the ambient wind, as the two are flowing at distinctly different velocities. The resulting vortex-like structures are analyzed with respect to what the Kelvin-Helmholtz instability predicts, and inferences are presented about what the local magnetic field strength and density must be to allow such an instability in this environment.

Expanding the frontiers of cool-dwarf asteroseismology with ESPRESSO

by T. L. Campante, H. Kjeldsen, Y. Li, M. N. Lund, A. M. Silva, et al in Astronomy & Astrophysics

An orange dwarf star has yielded the tiniest ‘starquakes’ ever recorded, measured by an international team of scientists.

Named Epsilon Indi, the star is the smallest and coolest dwarf star yet observed with solar-like oscillations — “starquakes” like those shown by the Sun. These oscillations provide indirect glimpses of stellar interiors — just as earthquakes tell us about Earth’s interior — and so are important sources of information about the makeup of the star.

The measurements were taken by an international team, led by the Institute of Astrophysics and Space Sciences in Portugal, and including researchers from the University of Birmingham.

The quakes were detected using a technique dubbed asteroseismology, which measures oscillations in stars. Using the ESPRESSO spectrograph, mounted at the European Southern Observatory’s (ESO) Very Large Telescope (VLT), the team was able to record the oscillations with unprecedented precision.

Lead author Tiago Campante, of the Institute of Astrophysics and Space Sciences at the University of Porto, said: “The extreme precision level of these observations is an outstanding technological achievement. Importantly, this detection conclusively shows that precise asteroseismology is possible down to cool dwarfs with surface temperatures as low as 4200 degrees Celsius, about 1000 degrees cooler than the Sun’s surface, effectively opening up a new domain in observational astrophysics.”

tellar radius–effective temperature diagram highlighting seismic detections from Kepler and TESS photometry (blue circles; Mathur et al. 2017; Hatt et al. 2023), and radial-velocity campaigns (red diamonds; see e.g., Arentoft et al. 2008; Kjeldsen et al. 2008, and references therein).

Orange dwarf stars have recently become a focus in the search for habitable planets and extraterrestrial life. Professor Bill Chaplin, Head of the School of Physics & Astronomy at Birmingham, and a member of the team, said: “The mismatch between the predicted and observed sizes of these stars has implications for finding planets around them. If we use the most successful planet-finding technique — the so-called transit method — we get the size of the planet relative to the size of the star; if we don’t size-up the star correctly, the same will be true of any small planet we have found.” The detection of oscillations will help to understand and minimise these discrepancies, and improve the theoretical models of stars.

The detection of starquakes in Epsilon Indi will now inform plans to use the upcoming European Space Agency’s (ESA) PLATO Mission, scheduled to be launched in 2026, to detect oscillations in many more orange dwarfs. PLATO will also be searching for planets around these stars. Birmingham has responsibility for the design and delivery of much of the asteroseismology pipeline for PLATO, the results of which will be used by thousands of researchers around the world.

Thermonuclear explosions on neutron stars reveal the speed of their jets

by Thomas D. Russell, Nathalie Degenaar, Jakob van den Eijnden, Thomas Maccarone, Alexandra J. Tetarenko, Celia Sánchez-Fernández, James C. A. Miller-Jones, Erik Kuulkers, Melania Del Santo in Nature

For the first time, astronomers have measured the speed of fast-moving jets in space, crucial to star formation and the distribution of elements needed for life.

The jets of matter, expelled by stars deemed ‘cosmic cannibals’, were measured to travel at over one-third of the speed of light — thanks to a groundbreaking new experiment. The study sheds new light on these violent processes, making clever use of runaway nuclear explosions on the surface of stars.

Co-Author Jakob van den Eijnden, Warwick Prize Fellow at the Department of Physics, University of Warwick, said: “The explosions occurred on neutron stars, which are incredibly dense and notorious for their enormous gravitational pull that makes them swallow gas from their surroundings — a gravitational pull that is only surpassed by black holes.

“The material, mostly hydrogen from a nearby star that orbits around, swirls towards the collapsed star, falling like snow across its surface. As more and more material rains down, the gravitational field compresses it until a runaway nuclear explosion is initiated. This explosion impacts the jets, that are also shot out from the infalling material and eject particles into space at very high speed.”

The team devised a way of measuring the speed and properties of the jets by comparing X-ray and radio signals picked up by the Australia Telescope Compact Array (owned and operated by CSIRO, Australia’s national science agency) and the European Space Agency’s (ESA’s) Integral satellite.

Co-Author Thomas Russell, National Institute for Astrophysics, INAF, Palermo, Italy, said: “This gave us a perfect experiment. We had a very brief short-lived impulse of extra material that gets shot into the jet and that we can track as it moves down the jet to learn about its speed.”
Jakob van den Eijnden added: “These explosion occur every couple of hours, but you can’t predict exactly when they will happen. So you have to stare at the telescope observations for a long time, and hope you catch a couple of bursts. Over three days of observations we saw 10 explosions and jets lighting up.”

The jets travelled around 114,000 kilometres per second, an incredible 35–40% the speed of light. This was the first time astronomers had been able to anticipate and directly watch how a certain amount of gas got channelled into a jet and accelerated into space.

Co-Author Nathalie Degenaar, University of Amsterdam, the Netherlands, continued: “Based on previous data, we thought the explosion would destroy the location where the jet was being launched. But we saw exactly the opposite: a strong input into the jet rather than a disruption.”

The researchers believe the mass and rotation of neutron stars and black holes also impacts the jets. Having now shown this research is possible, this study will form the blueprint for future experiments into neutron stars and their jets. Jets can also be produced by cataclysmic events such as supernova explosions and gamma-ray bursts. The new results will have wide applicability in many studies of the cosmos.