Saturday, December 20, 2025

NASA’s Webb Observes Exoplanet Whose Composition Defies Explanation

This artist’s concept shows what the exoplanet called PSR J2322-2650b (left) may look like as it orbits a rapidly spinning neutron star called a pulsar (right). Gravitational forces from the much heavier pulsar are pulling the Jupiter-mass world into a bizarre lemon shape. Illustration: NASA, ESA, CSA, Ralf Crawford (STScI)

This artist’s concept shows what the exoplanet PSR J2322-2650b may look like. Gravitational forces from the much heavier pulsar it orbits are pulling the Jupiter-mass world into this bizarre lemon shape. Illustration: NASA, ESA, CSA, Ralf Crawford (STScI)

Video A: Exoplanet PSR J2322-2650b and Pulsar (Artist's Concept)
This animation shows an exotic exoplanet orbiting a distant pulsar, or rapidly rotating neutron star with radio pulses. The planet, which orbits about 1 million miles away from the pulsar, is stretched into a lemon shape by the pulsar’s strong gravitational tides. Animation: NASA, ESA, CSA, Ralf Crawford (STScI)



Scientists using NASA’s James Webb Space Telescope have observed a rare type of exoplanet, or planet outside our solar system, whose atmospheric composition challenges our understanding of how it formed.

Officially named PSR J2322-2650b, this Jupiter-mass object appears to have an exotic helium-and-carbon-dominated atmosphere unlike any ever seen before. Soot clouds likely float through the air, and deep within the planet, these carbon clouds can condense and form diamonds. How the planet came to be is a mystery. The paper appears Tuesday in The Astrophysical Journal Letters.

“This was an absolute surprise,” said study co-author Peter Gao of the Carnegie Earth and Planets Laboratory in Washington. “I remember after we got the data down, our collective reaction was ‘What the heck is this?’ It's extremely different from what we expected.”

his planet-mass object was known to orbit a pulsar, a rapidly spinning neutron star. A pulsar emits beams of electromagnetic radiation at regular intervals typically ranging from milliseconds to seconds. These pulsing beams can only be seen when they are pointing directly toward Earth, much like beams from a lighthouse.

This millisecond pulsar is expected to be emitting mostly gamma rays and other high energy particles, which are invisible to Webb’s infrared vision. Without a bright star in the way, scientists can study the planet in intricate detail across its whole orbit.

“This system is unique because we are able to view the planet illuminated by its host star, but not see the host star at all,” said Maya Beleznay, a third-year PhD candidate at Stanford University in California who worked on modeling the shape of the planet and the geometry of its orbit. “So we get a really pristine spectrum. And we can study this system in more detail than normal exoplanets.”

“The planet orbits a star that's completely bizarre — the mass of the Sun, but the size of a city,” said the University of Chicago’s Michael Zhang, the principal investigator on this study. “This is a new type of planet atmosphere that nobody has ever seen before. Instead of finding the normal molecules we expect to see on an exoplanet — like water, methane, and carbon dioxide — we saw molecular carbon, specifically C3 and C2.”

Molecular carbon is very unusual because at these temperatures, if there are any other types of atoms in the atmosphere, carbon will bind to them. (Temperatures on the planet range from 1,200 degrees Fahrenheit at the coldest points of the night side to 3,700 degrees Fahrenheit at the hottest points of the day side.) Molecular carbon is only dominant if there's almost no oxygen or nitrogen. Out of the approximately 150 planets that astronomers have studied inside and outside the solar system, no others have any detectable molecular carbon.

PSR J2322-2650b is extraordinarily close to its star, just 1 million miles away. In contrast, Earth’s distance from the Sun is about 100 million miles. Because of its extremely tight orbit, the exoplanet’s entire year — the time it takes to go around its star — is just 7.8 hours. Gravitational forces from the much heavier pulsar are pulling the Jupiter-mass planet into a bizarre lemon shape.

Together, the star and exoplanet may be considered a “black widow” system, though not a typical example. Black widow systems are a rare type of double system where a rapidly spinning pulsar is paired with a small, low-mass stellar companion. In the past, material from the companion streamed onto the pulsar, causing the pulsar to spin faster over time, which powers a strong wind. That wind and radiation then bombard and evaporate the smaller and less massive companion. Like the spider for which it is named, the pulsar slowly consumes its unfortunate partner.

But in this case, the companion is officially considered an exoplanet, not a star. The International Astronomical Union defines an exoplanet as a celestial body below 13 Jupiter masses that orbits a star, brown dwarf, or stellar remnant, such as a pulsar.

Of the 6,000 known exoplanets, this is the only one reminiscent of a gas giant (with mass, radius, and temperature similar to a hot Jupiter) orbiting a pulsar. Only a handful of pulsars are known to have planets.

“Did this thing form like a normal planet? No, because the composition is entirely different,” said Zhang. “Did it form by stripping the outside of a star, like ‘normal’ black widow systems are formed? Probably not, because nuclear physics does not make pure carbon. It's very hard to imagine how you get this extremely carbon-enriched composition. It seems to rule out every known formation mechanism.”

Study co-author Roger Romani, of Stanford University and the Kavli Institute for Particle Astrophysics and Cosmology Institute, proposes one evocative phenomenon that could occur in the unique atmosphere. “As the companion cools down, the mixture of carbon and oxygen in the interior starts to crystallize,” said Romani. “Pure carbon crystals float to the top and get mixed into the helium, and that's what we see. But then something has to happen to keep the oxygen and nitrogen away. And that's where the mystery come in.

“But it's nice to not know everything,” said Romani. “I'm looking forward to learning more about the weirdness of this atmosphere. It's great to have a puzzle to go after.”

With its infrared vision and exquisite sensitivity, this is a discovery only the Webb telescope could make. Its perch a million miles from Earth and its huge sunshield keep the instruments very cold, which is necessary for these observations. It is not possible to conduct this study from the ground.

The James Webb Space Telescope is the world’s premier space science observatory. Webb is solving mysteries in our solar system, looking beyond to distant worlds around other stars, and probing the mysterious structures and origins of our universe and our place in it. Webb is an international program led by NASA with its partners, ESA (European Space Agency) and CSA (Canadian Space Agency).




Related Links:

Article : Webb’s Impact on Exoplanet Research

Interactive: ViewSpace Exoplanet Variety: Atmosphere

Video: How to Study Exoplanets: Webb and Challenges

Video: Black Widow Pulsars Consume Their Mates

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NASA's Roman Telescope Will Observe Thousands of Newfound Cosmic Voids


Measuring Cosmic Voids with the Roman Space Telescope
This narrated video sequence illustrates how the Roman Space Telescope will be able to observe cosmic voids in the universe. These highly detailed measurements will help constrain cosmological models. Credits/Video: NASA, STScI - Visualization: Frank Summers (STScI) - Script Writer: Frank Summers (STScI) - Narration: Frank Summers (STScI) - Audio: Danielle Kirshenblat (STScI). Science: Giulia Degni (Roma Tre University), Alice Pisani (CPPM), Giovanni Verza (Center for Computational Astrophysics/Flatiron Inst.)



Our universe is filled with galaxies, in all directions as far as our instruments can see. Some researchers estimate that there are as many as two trillion galaxies in the observable universe. At first glance, these galaxies might appear to be randomly scattered across space, but they’re not. Careful mapping has shown that they are distributed across the surfaces of giant cosmic “bubbles” up to several hundred million light-years across. Inside these bubbles, few galaxies are found, so those regions are called cosmic voids. NASA’s Nancy Grace Roman Space Telescope will allow us to measure these voids with new precision, which can tell us about the history of the universe’s expansion.
“Roman’s ability to observe wide areas of the sky to great depths, spotting an abundance of faint and distant galaxies, will revolutionize the study of cosmic voids,” said Giovanni Verza of the Flatiron Institute and New York University, lead author on a paper published in The Astrophysical Journal.

Cosmic Recipe

The cosmos is made of three key components: normal matter, dark matter, and dark energy. The gravity of normal and dark matter tries to slow the expansion of the universe, while dark energy opposes gravity to speed up the universe’s expansion. The nature of both dark matter and dark energy are currently unknown. Scientists are trying to understand them by studying their effects on things we can observe, such as the distribution of galaxies across space.

“Since they’re relatively empty of matter, voids are regions of space that are dominated by dark energy. By studying voids, we should be able to put powerful constraints on the nature of dark energy,” said co-author Alice Pisani of CNRS (the French National Centre for Scientific Research) in France and Princeton University in New Jersey.

To determine how Roman might study voids, the researchers considered one potential design of the Roman High-Latitude Wide-Area Survey, one of three core community surveys that Roman will conduct. The High-Latitude Wide-Area Survey will look away from the plane of our galaxy (hence the term high latitude in galactic coordinates). The team found that this survey should be able to detect and measure tens of thousands of cosmic voids, some as small as just 20 million light-years across. Such large numbers of voids will allow scientists to use statistical methods to determine how their observed shapes are influenced by the key components of the universe.

To determine the actual, 3D shapes of the voids, astronomers will use two types of data from Roman — the positions of galaxies in the sky and their cosmological redshift, the latter of which is determined using spectroscopic data. To convert redshift to a physical distance, astronomers make assumptions about the components of the universe, including the strength of dark energy and how it might have evolved over time.

Pisani compared it to trying to infer a cake recipe (i.e., the universe’s makeup) from the final dessert served to you. “You try to put in the right ingredients — the right amount of matter, the right amount of dark energy — and then you check whether your cake looks as it should. If it doesn’t, that means you put in the wrong ingredients.”

In this case, the appearance of the “cake” is the shape found by statistically stacking all of the voids detected by Roman on top of each other. On average, voids are expected to have a spherical shape because there is no “preferred” location or direction in the universe (i.e., the universe is both homogeneous and isotropic on large scales). This means that, if the stacking is done correctly, the resulting shape will be perfectly round (or spherically symmetric). If not, then you have to adjust your cosmic recipe.

Power of Roman

The researchers emphasized that to study cosmic voids in large numbers, an observatory must be able to probe a large volume of the universe, because the voids themselves can be tens or hundreds of millions of light-years across. The spectroscopic data necessary to study voids will come from a portion of the Roman High-Latitude Wide-Area Survey that will cover on the order of 2,400 square degrees of the sky, or 12,000 full moons. It will also be able to see fainter and more distant objects, yielding a greater density of galaxies than complementary missions like ESA’s (European Space Agency’s) Euclid.

“Voids are defined by the fact that they contain so few galaxies. So to detect voids, you have to be able to observe galaxies that are quite sparse and faint. With Roman, we can better look at the galaxies that populate voids, which ultimately will give us greater understanding of the cosmological parameters like dark energy that are sculpting voids,” said co-author Giulia Degni of Roma Tre University and INFN (the National Institute of Nuclear Physics) in Rome.

The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory in Southern California; Caltech/IPAC in Pasadena, California; the Space Telescope Science Institute in Baltimore; and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc. in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.




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Friday, December 19, 2025

Massive non-cool-core galaxy cluster explored with Chandra

Exposure-corrected 0.5–7 keV Chandra ACIS-I0–3 image of SPT-CL J0217-5014. The source extraction region, centered on the X-ray centroid, is shown by a white circle. The regions used for local background extraction are also indicated. All point sources were excluded from both the source and background regions during imaging and spectral analysis. Credit: arXiv (2025). DOI: 10.48550/arxiv.2512.04689



Astronomers have employed NASA's Chandra spacecraft to perform X-ray observations of a massive galaxy cluster known as SPT-CL J0217-5014. Results of the observational campaign, published December 4 on the arXiv preprint server, yield important insights into the properties and nature of this cluster.

Enormous gravitationally-bound structures

Galaxy clusters contain up to thousands of galaxies bound together by gravity. They form through accretion of mass and infall of smaller sub-structures and are the largest known gravitationally-bound structures in the universe. Astronomers perceive galaxy clusters as excellent laboratories for studying galaxy evolution and cosmology.

SPT-CL J0217-5014 is a galaxy cluster at a redshift of 0.53, with a stellar mass of about 300 trillion solar masses, and super-solar iron abundance. Given that very little is known regarding the properties of this cluster, a team of astronomers led by Dan Hu of Masaryk University in Brno, Czech Republic, decided to investigate it with Chandra's Advanced CCD Imaging Spectrometer (ACIS)-I array.

"This study aims to evaluate its chemical and thermodynamic properties with a dedicated Chandra observation," the researchers write.

Disturbed non-cool-core cluster

Chandra imaging revealed that SPT-CL J0217-5014 has a disturbed morphology, characterized by a surface brightness edge at about 330,000 light years to the west and a tail-like feature extending to the east. Such morphology suggests a disturbed, non-relaxed intracluster medium (ICM).

Furthermore, the collected data indicate that SPT-CL J0217-5014 is a non-cool-core cluster. It turned out that the cluster has a sub-solar abundance, which is consistent with the typical metallicities observed in non-cool-core clusters. The astronomers explained that in such clusters, the dynamical processes could disrupt the cool core and tend to mix the central metal-rich gas with the outer ICM.

The study found that the power ratio and morphology index of SPT-CL J0217-5014 clearly place it in the dynamically disturbed regime. This suggests that the cluster may have experienced a merger event.

Potential companions of SPT-CL J0217-5014

The observation also resulted in the identification of three potential galaxy clusters near SPT-CL J0217-5014, which received the designations CIG 2, CIG 3, and CIG 4. They have lower mass and are less enriched than SPT-CL J0217-5014. This finding indicates that SPT-CL J0217-5014 is the primary, most massive cluster in this complex and likely sits at a node of the surrounding large-scale structure. "SPT-CL J0217–5014 likely underwent a relatively energetic, nearly head-on merger that disrupted a pre-existing cool core; ClG 2 and ClG 3 may be lower-mass companions that have merged with or fallen onto the main cluster, while ClG 4 aligns with the extension of the filamentary galaxy distribution, suggesting its association with a broader cosmic web," the authors conclude.




Written for you by our author: Tomasz Nowakowski, edited by Stephanie Baum, and fact-checked and reviewed by Robert Egan—this article is the result of careful human work. We rely on readers like you to keep independent science journalism alive. If this reporting matters to you, please consider a donation (especially monthly). You'll get an ad-free account as a thank-you.



More information: Dan Hu et al, A Chandra view of SPT-CL J0217-5014: a massive galaxy cluster at a cosmic intersection at z=0.53, arXiv (2025). DOI: 10.48550/arxiv.2512.04689

Journal information: arXiv

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X-ray observations reveal dynamic features of galaxy cluster PLCKG287


Thursday, December 18, 2025

Mining asteroids for water and metals explored

Carbonaceous chondrite meteorite
Credit: J.M.Trigo-Rodríguez/ICE-CSIC
Licence type: Attribution (CC BY 4.0)



The potential for space mining – including identifying asteroids close to Mars and Jupiter best suited for extracting precious metals and water – has been explored in a new study.

Research published in Monthly Notices of the Royal Astronomical Society looked into how viable the idea would be in the future.

Much is still unknown about the chemical composition of small asteroids but their potential to harbour valuable metals, materials from the early solar system, and the possibility of obtaining a geochemical record of their parent bodies makes them promising candidates for future use of space resources.

A team led by the Institute of Space Sciences (ICE-CSIC) in Spain analysed meteorites that had fallen to Earth, including from NASA’s Antarctic collection, to determine the chemical composition of the six most common groups of carbonaceous chondrites.

Their findings support the idea that these asteroids can serve as crucial material sources and identify their parent bodies, as well as for planning future missions and developing new technologies for resource exploitation.

Several proposals have already been put forward, such as capturing small asteroids that pass close to Earth and placing them in a circumlunar orbit for exploitation.

“For certain water-rich carbonaceous asteroids, extracting water for reuse seems more viable, either as fuel or as a primary resource for exploring other worlds,” said Dr Josep Trigo-Rodríguez, first author of the study and astrophysicist at ICE-CSIC, affiliated to the Institute of Space Studies of Catalonia (IEEC).

“This could also provide science with greater knowledge about certain bodies that could one day threaten our very existence. In the long term, we could even mine and shrink potentially hazardous asteroids so that they cease to be dangerous.”

Carbonaceous chondrites are relatively rare – making up just 5 per cent of meteorite falls – and many of them are so fragile that they fragment and are never recovered. Those that have been are usually found in desert regions, such as the Sahara or Antarctica.

“The scientific interest in each of these meteorites is that they sample small, undifferentiated asteroids, and provide valuable information on the chemical composition and evolutionary history of the bodies from which they originate,” Dr Trigo-Rodríguez explained.

Pau Grèbol Tomás, ICE-CSIC predoctoral researcher, said: “Studying and selecting these types of meteorites in our clean room and using other analytical techniques is fascinating, particularly because of the diversity of minerals and chemical elements they contain.

“However, most asteroids have relatively small abundances of precious elements, and therefore the objective of our study has been to understand to what extent their extraction would be viable.”

Study co-author Jordi Ibáñez-Insa, of the Geosciences Barcelona (GEO3BCN-CSIC), said: “Although most small asteroids have surfaces covered in fragmented material called regolith – and it would facilitate the return of small amounts of samples – developing large-scale collection systems to achieve clear benefits is a very different matter.

“In any case, it deserves to be explored because the search for resources in space would likely minimise the impact of mining activities on terrestrial ecosystems.”

Given the diversity present in the main asteroid belt, it is crucial to define what types of resources could be found there.

“They are small and quite heterogeneous objects, heavily influenced by their evolutionary history, particularly collisions and close approaches to the Sun,” said Dr Trigo-Rodríguez.

“If we are looking for water, there are certain asteroids from which hydrated carbonaceous chondrites originate, which, conversely, will have fewer metals in their native state.

“Let's not forget that, after 4.56 billion years since their formation, each asteroid has a different composition, as revealed by the study of chondritic meteorites.”

One of the study's conclusions is that mining undifferentiated asteroids – the primordial remnants of the solar system's formation considered the progenitor bodies of chondritic meteorites – is still far from viable.

On the other hand, the study points to a type of pristine asteroid with olivine and spinel bands as a potential target for mining. A comprehensive chemical analysis of carbonaceous chondrites is essential to identify promising targets for space mining.

However, the team states that this effort must be accompanied by new sample-return missions to verify the identity of the progenitor bodies.

“Alongside the progress represented by sample return missions, companies capable of taking decisive steps in the technological development necessary to extract and collect these materials under low-gravity conditions are truly needed,” Dr Trigo-Rodríguez added.

“The processing of these materials and the waste generated would also have a significant impact that should be quantified and properly mitigated.”

The team is confident of very short-term progress, given that the use of in-situ resources will be a key factor for future long-term missions to the Moon and Mars, reducing dependence on resupply from Earth.

In this regard, the authors point out that if water extraction were the goal, water-altered asteroids with a high concentration of water-bearing minerals should be selected. Exploiting these resources under low-gravity conditions requires the development of new extraction and processing techniques.

“It sounds like science fiction, but it also seemed like science fiction when the first sample return missions were being planned 30 years ago,” said Grèbol Tomàs.

The scientific team from ICE-CSIC selected, characterised, and provided the asteroid samples, which were analysed using mass spectrometry at the University of Castilla-La Mancha by Professor Jacinto Alonso-Azcárate.

This allowed them to determine the precise chemical abundances of the six most common classes of carbonaceous chondrites, fostering the discussion among the scientific community of whether their future extraction would be feasible.

The Asteroids, Comets, and Meteorites research group at ICE-CSIC investigates the physicochemical properties of the materials that make up the surfaces of asteroids and comets and has made numerous contributions in this field over the last decade.

“At ICE-CSIC and IEEC, we specialise in developing experiments to better understand the properties of these asteroids and how the physical processes that occur in space affect their nature and mineralogy,” said Dr Trigo-Rodríguez, who leads this group.

For over a decade he has been involved in selecting and requesting from NASA the carbonaceous chondrites analysed in this study, as well as devising several experiments with them.

"The work now being published is the culmination of that team effort," Dr Trigo-Rodríguez added.




Media contacts:

Sam Tonkin
Royal Astronomical Society
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press@ras.ac.uk

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Science contacts:

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ICE-CSIC

trigo@ice.csic.es



Images & captions

Carbonaceous chondrite meteorite

Caption: Reflected light image of a thin section of carbonaceous chondrite CV3 from NASA's Antarctic collection, analysed in the study. Several chondrules with bright olivine crystals embedded in a carbonaceous matrix can be seen. Credit: J.M.Trigo-Rodríguez/ICE-CSIC



Further information

The paper ‘Assessing the metal and rare earth element mining potential of undifferentiated asteroids through the study of carbonaceous chondrites’ by J.M. Trigo-Rodríguez et al. has been published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/staf1902.



Notes for editors

About the Royal Astronomical Society

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The RAS organises scientific meetings, publishes international research and review journals, recognises outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4,000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

The RAS accepts papers for its journals based on the principle of peer review, in which fellow experts on the editorial boards accept the paper as worth considering. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content.

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Submitted by Sam Tonkin on Wed, 10/12/2025 - 09:00


Wednesday, December 17, 2025

Astronomers Create First Map of the Sun's Outer Boundary

This artist's conception shows the boundary in the Sun's atmosphere where the speed of the outward solar wind becomes faster than the speed of magnetic waves. The area appears to shift between spiky and frothy, and is the point of no return for material that escapes the Sun's magnetic grasp. Deep dives into the Alfvén surface using NASA's Parker Solar Probe combined with far-away measurements, have allowed scientists to track the evolution of this structure throughout the solar cycle and produce a map of this previously uncharted territory. Credit: CfA/ Melissa Weiss.
Low Resolution Image



Using NASA’s Parker Solar Probe and other near-Earth spacecraft, scientists from the Center for Astrophysics | Harvard & Smithsonian have made and validated the first 2D maps of the Sun’s outer surface, leading to unprecedented insight into how and where the Sun “loses its grip” on its outer atmosphere.

Cambridge, MA (December 11, 2025)— Astronomers have produced the first continuous, two-dimensional maps of the outer edge of the Sun’s atmosphere, a shifting, frothy boundary that marks where solar winds escape the Sun’s magnetic grasp. By combining the maps and close-up measurements, scientists from the Center for Astrophysics | Harvard & Smithsonian (CfA) showed that the boundary grows larger, rougher and spikier as the Sun becomes more active. The findings could help scientists improve models showing how the Sun affects Earth, and better predict atmospheric complexity for other stars.

“Parker Solar Probe data from deep below the Alfvén surface could help answer big questions about the Sun’s corona, like why it’s so hot. But to answer those questions, we first need to know exactly where the boundary is,” said Sam Badman, an astrophysicist at the CfA, and the lead author of the paper.

The scientists have directly validated these maps using deep dives into the Sun’s atmosphere made by NASA’s Parker Solar Probe. The findings are published today in the Astrophysical Journal Letters (ApJL).

The boundary in the Sun’s atmosphere where the solar wind’s outward speed becomes faster than the speed of magnetic waves, known as the Alfvén surface, is the “point of no return” for material that escapes the Sun and enters interplanetary space; once material travels beyond this point, it cannot travel back to the Sun. This surface is the effective “edge” of the Sun’s atmosphere, and provides scientists with an active laboratory for studying and understanding how solar activity impacts the rest of the solar system, including life and technology on and around Earth.

Using Parker’s Solar Wind Electrons Alphas and Protons (SWEAP) instrument, developed by the CfA in conjunction with the University of California, Berkeley, the scientists collected data from deep into the Sun’s sub-Alfvénic surface.

“There are still a number of fascinating physics questions about the Sun’s corona that we don’t fully understand,” said Michael Stevens, an astronomer at the CfA and the principal investigator of Parker’s SWEAP instrument. “This work shows without a doubt that Parker Solar Probe is diving deep with every orbit into the region where the solar wind is born. We are now headed for an exciting period where it will witness firsthand how those processes change as the Sun goes into the next phase of its activity cycle.”

“Before, we could only estimate the Sun’s boundary from far away without a way to test if we got the right answer, but now we have an accurate map that we can use to navigate it as we study it,” added Badman “And, importantly, we also are able to watch it as it changes and match those changes with close-up data. That gives us a much clearer idea of what’s really happening around the Sun.”

Scientists previously knew this boundary changes dynamically with solar cycles, moving away from the Sun and becoming larger, more structured, and more complex during solar maximum, and the opposite during solar minimum, but until now didn’t have confirmation of what exactly those changes looked like.

Badman added, “As the Sun goes through activity cycles, what we’re seeing is that the shape and height of the Alfvén surface around the Sun is getting larger and also spikier. That’s actually what we predicted in the past, but now we can confirm it directly.”

The new maps and corresponding data can help scientists answer important questions about the physics happening deep in the Sun’s atmosphere; that knowledge can in turn be used to develop better solar wind and space-weather models, sharpening forecasts of how solar activity moves through and shapes the environment around Earth and other planets in the solar system.

It can also help them to answer longheld questions about the lives of stars elsewhere in the galaxy and the universe, from how they’re born to how they behave throughout their lives, including how that behavior influences the habitability of their orbiting planets.

The team’s findings offer a new window into the workings of our closest star and lay the foundation for ever deeper discoveries. According to Badman, the coordinated multi-spacecraft approach, which combined the observational powers of close-up probes and distant observing stations including the Solar Orbiter, a project of NASA and the European Space Agency (ESA), and NASA’s Wind spacecraft, will continue to serve as a model for future breakthrough studies in heliophysics. During the next solar minimum, the team will again dive into the Sun’s corona, with an aim to study how it evolves over a complete solar cycle.




Resource

Badman, S. T. et al, “Multi-spacecraft measurements of the evolving geometry of the Solar Alfvén surface over half a solar cycle,” Astrophysical Journal Letters, 2025 Dec 11, doi: 10.3847/2041-8213/ae0e5c



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Astronomers find first direct evidence of “Monster Stars” from the cosmic dawn

While measuring chemical signatures in galaxy GS 3073, scientists determined that the ratio of nitrogen to oxygen was too high to be explained by ordinary stars. Instead, the extreme levels of nitrogen point to primordial monster stars between 1,000 and 10,000 times the mass of the Sun. This simulated image shows the birth of a primordial quasar, or extraordinarily bright black hole, that was made possible by one of these giant stars. Credit: Nandal et al.

Scientists have found the first observational evidence of supermassive “first stars” that formed in rare, turbulent streams of cold gas in the early universe. This new data is helping scientists confirm theories about how quasars, or extremely bright black holes, 9174mwere able to form less than a billion years after the Big Bang. Credit: Nandal et al.
Download video here (174 Mb)



Using the James Webb Space Telescope, an international team of researchers led the Center for Astrophysics | Harvard & Smithsonian have discovered chemical fingerprints of gigantic primordial stars that were among the first to form after the Big Bang.

Cambridge, MA (December 9, 2025)— For two decades, astronomers have puzzled over how supermassive black holes, which are some of the brightest objects in the universe, could exist less than a billion years after the Big Bang. Normal stars simply couldn't create such massive black holes quickly enough.

Now, using NASA’s James Webb Space Telescope (JWST), an international team of astronomers has found the first compelling evidence that solves this cosmic mystery: “monster stars” weighing between 1,000 and 10,000 times the mass of our Sun existed in the early universe. The breakthrough came from examining chemical signatures in a galaxy called GS 3073.

A new study led by scientists from the Center for Astrophysics | Harvard & Smithsonian (CfA) and the University of Portsmouth in England has discovered an extreme imbalance of nitrogen to oxygen that cannot be explained by any known type of star.

In 2022, researchers published work in Nature predicting that supermassive stars naturally formed in rare, turbulent streams of cold gas in the early universe, explaining how quasars (extraordinarily bright black holes) could exist less than a billion years after the Big Bang.

“Our latest discovery helps solve a 20-year cosmic mystery,” said Daniel Whalen from the University of Portsmouth's Institute of Cosmology and Gravitation. “With GS 3073, we have the first observational evidence that these monster stars existed.

These cosmic giants would have burned brilliantly for a brief time before collapsing into massive black holes, leaving behind the chemical signatures we can detect billions of years later. A bit like dinosaurs on Earth, they were enormous and primitive. And they had short lives, living for just a quarter of a million years, a cosmic blink of an eye.”

The key to the discovery was measuring the ratio of nitrogen to oxygen in GS 3073. The galaxy contains a nitrogen-to-oxygen ratio of 0.46, far higher than can be explained by any known type of star or stellar explosion.

Devesh Nandal, a Swiss National Science Foundation postdoctoral fellow at the CfA’s Institute for Theory and Computation said, “Chemical abundances act like a cosmic fingerprint, and the pattern in GS 3073 is unlike anything ordinary stars can produce. Its extreme nitrogen matches only one kind of source we know of: primordial stars thousands of times more massive than our Sun. This tells us the first generation of stars included truly supermassive objects that helped shape the early galaxies and may have seeded today’s supermassive black holes.”

The researchers modeled how stars between 1,000 and 10,000 solar masses evolve and what eleme,brnts they produce. They found a specific mechanism that creates massive amounts of nitrogen:

  • These enormous stars burn helium in their cores, producing carbon;

  • The carbon leaks into a surrounding shell where hydrogen is burning;

  • The carbon combines with hydrogen to create nitrogen through the carbon/nitrogen/oxygen (CNO) cycle;

  • Convection currents distribute the nitrogen throughout the star; and,

  • Eventually, this nitrogen-rich material is shed into space, enriching the surrounding gas.

The process continues for millions of years during the star's helium-burning phase, creating the nitrogen excess observed in GS 3073.

The models, published in the Astrophysical Journal Letters, also predict what happens when these monster stars die. They don't explode. Instead, they collapse directly into massive black holes weighing thousands of solar masses.

Interestingly, GS 3073 contains an actively feeding black hole at its center, potentially the very remnant of one of these supermassive first stars. If confirmed, this would solve two mysteries at once: where the nitrogen came from and how the black hole formed.

The study also found that this nitrogen signature only appears in a specific mass range. Stars smaller than 1,000 solar masses or larger than 10,000 solar masses don't produce the right chemical pattern for the signature, suggesting a "sweet spot" for this type of enrichment.

These findings open a new window into the universe's first few hundred million years, a period astronomers call the "cosmic Dark Ages" when the first stars ignited and began transforming the simple chemistry of the early universe into the rich variety of elements we see today.

The researchers predict that JWST will find more galaxies with similar nitrogen excesses as it continues surveying the early universe. Each new discovery will strengthen the case for these ultra-massive first stars.




Resource:

Nandal, D. et al, “1000-10,000 M ⊙ Primordial Stars Created the Nitrogen Excess in GS 3073 at z = 5.55,” The Astrophysical Journal Letters, doi: 10.3847/2041-8213/ae1a63



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Tuesday, December 16, 2025

Galactic gas makes a getaway

A spiral galaxy seen nearly edge-on. Its disk is filled with red and blue lights from star-forming nebulae and clusters of hot stars, respectively, as well as thick dark clouds of dust that block the strong white light from its centre. A faint, glowing halo of gas surrounds the disc, fading into the black background. A bluish plume of gas also extends from the galaxy’s core to the lower-right of the image. Credit: ESA/Hubble & NASA, S. Veilleux, J. Wang, J. Greene

A sideways spiral galaxy shines in today’s ESA/Hubble Picture of the Week. Located about 60 million light-years away in the constellation Virgo (The Maiden), NGC 4388 is a resident of the Virgo galaxy cluster. The Virgo cluster contains more than a thousand galaxies and is the nearest large galaxy cluster to the Milky Way.

NGC 4388 is tilted at an extreme angle relative to our point of view, giving us a nearly edge-on vantage point. This perspective reveals a curious feature that wasn’t visible in a previous Hubble image of this galaxy released in 2016: a plume of gas from the galaxy’s nucleus, here seen billowing out from the galaxy’s disc towards the lower-right corner of the image. But where did this outflow come from, and why does it glow?

The answer likely lies in vast stretches that separate the galaxies of the Virgo cluster. Though the space between the galaxies appears to be empty, this space is actually occupied by hot wisps of gas called the intracluster medium. As NGC 4388 journeys within the cluster, it plunges through the intracluster medium. The pressure from the hot intracluster gas whisks away the gas from within NGC 4388’s disc, causing it to trail behind as NGC 4388 moves.

The source of the energy that ionises this gas cloud and causes it to glow is more uncertain. Researchers suspect that some of the energy comes from the centre of the galaxy, where a supermassive black hole has spun the gas around it into a superheated disc. The blazing radiation from this disc might ionise the gas closest to the galaxy, while shock waves might be responsible for ionising the filaments of gas farther out.

This image incorporates new data including several additional wavelengths of light to bring the ionised gas cloud into view. The data used to create this image come from several observing programmes that aim to illuminate galaxies with active black holes at their centres.



Painting Galaxy Clusters by Numbers (and Physics)

MS 0735.6+7421 - Perseus Cluster - M87 - Abell 2052 - Cygnus A
Credit: X-ray: NASA/CXC/Univ. of Chicago/H. McCall


JPEG (168.9 kb) - Large JPEG (10.5 MB) - Tiff (34.6 MB) - More Images

MS 0735.6+7421 - Perseus Cluster - M87 - Abell 2052 - Cygnus A
Astronomical Images of Objects Processed Using X-arithmetic Technique (Labeled) Credit: X-ray: NASA/CXC/Univ. of Chicago/H. McCall; Image processing: NASA/CXC/SAO/N. Wolk

A Tour of X-arithmetic - More Videos



Galaxy clusters are the most massive objects in the universe held together by gravity, containing up to several thousand individual galaxies and huge reservoirs of superheated, X-ray-emitting gas. The mass of this hot gas is typically about five times higher than the total mass of all the galaxies in galaxy clusters. In addition to these visible components, 80% of the mass of galaxy clusters is supplied by dark matter. These cosmic giants are bellwethers not only for the galaxies, stars and black holes within them, but also for the evolution and growth of the universe itself.

It is no surprise then that NASA’s Chandra X-ray Observatory has observed many galaxy clusters over the lifetime of the mission. Chandra’s X-ray vision allows it to see the enormous stockpiles of hot cluster gas, with temperatures as high as 100 million degrees, with exquisite clarity. This blazing gas tells stories about past and present activity within galaxy clusters.

Many of these galaxy clusters host supermassive black holes at their centers, which periodically erupt in powerful outbursts. These explosions generate jets that are visible in radio wavelengths, which inflate bubbles full of energetic particles; these bubbles carry energy out into the surrounding gas. Chandra’s images have revealed a wealth of other structures formed during these black hole outbursts, including hooks, rings, arcs, and wings. However, appearances alone don’t tell us what these structures are or how they formed.

To tackle this problem, a team of astronomers developed a novel image-processing technique to analyze X-ray data, allowing them to identify features in the gas of galaxy clusters like never before, classifying them by their nature rather than just their appearance. Prior to this technique, which they call “X-arithmetic,” scientists could only identify the nature of some of the features and in a much less efficient way, via studies of the amounts of X-ray energy dispersed at different wavelengths. The authors applied X-arithmetic to 15 galaxy clusters and galaxy groups (these are similar to galaxy clusters but with fewer member galaxies). By comparing the outcome from the X-arithmetic technique to computer simulations, researchers now have a new tool that will help in understanding the physical processes inside these important titans of the universe.

A new paper looks at how these structures appear in different parts of the X-ray spectrum. By splitting Chandra data into lower-energy and higher-energy X-rays and comparing the strengths of each structure in both, researchers can classify them into three distinct types, which they have colored differently. A pink color is given to sound waves and weak shock fronts, which arise from pressure disturbances traveling at close to the speed of sound, compressing the hot gas into thin layers. The bubbles inflated by jets are colored yellow, and cooling or slower-moving gas is blue. The resulting images, “painted” to reflect the nature of each structure, offer a new way to interpret the complex aftermath of black hole activity using only X-ray imaging data. This method works not only on Chandra (and other X-ray) observations, but also on simulations of galaxy clusters, providing a tool to bridge data and theory.

The images in this new collection show the central regions of five galaxy clusters in the sample: Abell 2052 and Cygnus A in the top row and MS 0735+7421, the Perseus Cluster, and M87 in the Virgo Cluster on the bottom row. All of these objects have been released to the public before by the Chandra X-ray Center, but this is the first time this special technique has been applied. The new treatment highlights important differences between the galaxy clusters and galaxy groups in the study.

The galaxy clusters in the study often have large regions of cooling or slow-moving gas near their centers, and only some show evidence for shock fronts. The galaxy groups, on the other hand, are different. They show multiple shock fronts in their central regions and smaller amounts of cooling and slow-moving gas compared to the sample of galaxy clusters.

This contrast between galaxy clusters and galaxy groups suggests that black hole feedback — that is, the interdependent relationship between outbursts from a black hole and its environment — appears stronger in galaxy groups. This may be because feedback is more violent in the groups than in the clusters, or because a galaxy group has weaker gravity holding the structure together than a galaxy cluster. The same outburst from a black hole, with the same power level, can therefore more easily affect a galaxy group than a galaxy cluster.

There are still many open questions about these black hole outbursts. For example, scientists would like to know how much energy they put into the gas around them and how often they occur. These violent events play a key role in regulating the cooling of the hot gas and controlling the formation of stars in clusters. By revealing the physics underlying the structures they leave behind, the X-arithmetic technique brings us closer to understanding the influence of black holes on the largest scales.

A paper describing this new technique and its results has been published in The Astrophysical Journal and is led by Hannah McCall from the University of Chicago. The other authors are Irina Zhuravleva (University of Chicago), Eugene Churazov (Max Planck Institute for Astrophysics, Germany), Congyao Zhang (University of Chicago), Bill Forman and Christine Jones (Center for Astrophysics | Harvard & Smithsonian), and Yuan Li (University of Massachusetts at Amherst).

NASA's Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory's Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.




Visual Description:

This release includes two sets of images featuring galaxy clusters. The first set of five images are traditional composite renderings. The second set of images features the same galaxy clusters rendered with a new image-processing technique called "X-arithmetic".

The traditional composite renderings share many visual similarities with digital photography; the images are relatively crisp, and feature cloud-like objects with blended colors, set against black backgrounds, dotted with distant specks of light. The X-arithmetic images are more visually similar to color MRI scans; they feature pixelated objects with distinct patches of vibrant color, set against neutral black backgrounds.

The first image in the two sets features the seemingly spherical galaxy cluster Abell 2052. In the composite rendering, the cluster resembles a pink rose in a cloud of powder blue haze. In the X-arithmetic rendering, interwoven pockets of hot pink, neon blue, and golden yellow appear brighter near the center, and somewhat muted near the outer edges.

The second image in the two sets features Cygnus A, a galaxy cluster with jets blasting in opposite directions out of a central black hole. In the composite image, the black hole appears as bright white light, the cluster resembles a neon blue cloud, and the jets exiting the cluster are surrounded by plumes resembling red smoke. In the X-arithmetic rendering, Cygnus A is depicted as a marbled ball of pixelated pockets in neon pink, blue, and golden yellow.

The third image in the sets features the galaxy cluster MS 0735. In the composite rendering, a vertical red cloud squiggle with a bright yellow dot in the center, is surrounded by a faint blue haze. In the X-arithmetic rendering, large pockets of yellow are surrounded by irregular hot pink shapes and dappled pockets of blue, which grow more granular near the outer edges.

The fourth pair of images feature the Perseus Cluster. The composite rendering resembles the view down a swirling cone of pink cotton candy, with a collection of dark blue filaments at the distant center. In the X-arithmetic rendering, the cluster resembles a corkscrew swirl of neon blue water, dotted with pink flecks, and blobs of golden yellow.

The fifth and final pair of images feature the galaxy cluster M87. In the composite rendering, the cluster is presented as ethereal overlapping clouds in purple, red, and white, with a golden orange embryonic shape at the core. The X-arithmetic rendering of the same cluster resembles a faint yellow cloud, digitally spattered with blue and pink pixels.



Fast Facts for MS 0735.6+7421:

Credit: X-ray: NASA/CXC/Univ. of Chicago/H. McCall
Release Date: December 9, 2025
Scale: Image is about 4.0 arcmin (2.8 million light-years) across.
Category: Groups and Clusters of Galaxies
Coordinates (J2000): RA 07h 41m 50.20s | Dec +74° 14´ 51.00"
Constellation: Camelopardalis
Observation Dates: 9 observations from Nov 2003 to Jan 2015
Observation Time: 149 hours 27 minute (6 days 5 hours 27 minutes)
Obs. ID: 4197, 10468-10471, 10822, 10918, 10922, 16275
Instrument:
ACIS
References: McCall, H. et al, 2025, ApJ, 989,159; DOI 10.3847/1538-4357/adea67
Color Code: X-ray: pink, yellow, blue
Distance Estimate: About 2.6 billion light-years from Earth



Fast Facts for Perseus Cluster:

Credit: X-ray: NASA/CXC/Univ. of Chicago/H. McCall
Release Date: December 9, 2025
Scale: Image is about 6 arcmin (410,000 light-years) across.
Category: Groups and Clusters of Galaxies
Coordinates (J2000): RA 3h 19m 47.60 | Dec +41° 30´ 37.00"
Constellation: Perseus
Observation Dates: 16 observations from Aug 2002 to Dec 2009
Observation Time: 330 hours 14 minutes (13 days 18 hours 14 minutes)
Obs. ID: 3209, 4289, 4946-4949, 6139, 4951-4953, 6139, 6145, 6146, 11713-11716
Instrument: ACIS
References: McCall, H. et al, 2025, ApJ, 989,159; DOI 10.3847/1538-4357/adea67
Color Code: X-ray: pink, yellow, blue
Distance Estimate: About 240 million light-years from Earth



Fast Facts for M87:

Credit: X-ray: NASA/CXC/Univ. of Chicago/H. McCall
Release Date: December 9, 2025v Scale: Image is about 15 arcmin (230,000 light-years) across.
Category: Groups and Clusters of Galaxies
Coordinates (J2000): RA 12h 30m 49.19s | Dec +12° 22´ 47.86"
Constellation: Virgo
Observation Dates: 10 observations from Jul 2003 to Apr 2010
Observation Time: 174 hours 26 minutes (7 days 6 hours 26 minutes)
Obs. ID: 2707, 3717, 5826-5828, 6186, 7210-7212, 11783
Instrument: ACIS
References: McCall, H. et al, 2025, ApJ, 989,159; DOI 10.3847/1538-4357/adea67
Color Code: X-ray: pink, yellow, blue
Distance Estimate: About 54 million light-years from Earth



Fast Facts for Abell 2052:

Credit: X-ray: NASA/CXC/Univ. of Chicago/H. McCall
Release Date: December 9, 2025
Scale: Image is about 4.4 arcmin (600,000 light-years) across.
Category: Groups and Clusters of Galaxies
Coordinates (J2000): RA 15h 16m 44.40s | Dec +07° 01´ 20.00"
Constellation: Serpens
Observation Dates: 10 observations from Mar, 2006 to Jun, 2009
Observation Time: 171 hours 28 minutes (7 days 3 hours 28 minutes)
Obs. ID: 5807, 10477-10480, 10879, 10914-10917
Instrument: ACIS
References: McCall, H. et al, 2025, ApJ, 989,159; DOI 10.3847/1538-4357/adea67
Color Code: X-ray: pink, yellow, blue
Distance Estimate: About 480 million light-years from Earth



Fast Facts for Cygnus A:

Credit: X-ray: NASA/CXC/Univ. of Chicago/H. McCall
Release Date: December 9, 2025
Scale: Image is about 3.4 arcmin (740,000 light-years) across.
Category: Groups and Clusters of Galaxies
Coordinates (J2000): RA 19h 59m 28.3s | Dec +44° 44´ 02"
Constellation: Cygnus
Observation Dates: 26 observations from Feb 2005 to May 2017
Observation Time: 221 hours 5 minutes (9 days 5 hours 5 minutes)
Obs. ID: 5830, 5831, 6225, 6226, 6228, 6229, 6250, 6252, 17133-17136, 17507-17514, 18688, 18871, 19989, 19996, 20077, 20079
Instrument: ACIS
References: McCall, H. et al, 2025, ApJ, 989,159; DOI 10.3847/1538-4357/adea67
Color Code: X-ray: pink, yellow, blue
Distance Estimate: About 760 million light-years from Earth


Monday, December 15, 2025

Michelangelo in Space: A Planet Carving the Fomalhaut Debris Disk?

This image combines observations from the Hubble Space Telescope and the Atacama Large Millimeter/submillimeter Array to show the dusty debris disk surrounding the star Fomalhaut. Credit:
ALMA (ESO/NAOJ/NRAO). Visible light image: the NASA/ESA Hubble Space Telescope A. Fujii/Digitized Sky Survey 2. Acknowledgment: Davide De Martin (ESA/Hubble); CC BY 4.0



Title:ALMA Reveals an Eccentricity Gradient in the Fomalhaut Debris Disk
Authors: Joshua B. Lovell et al.
First Author’s Institution: Center for Astrophysics | Harvard & Smithsonian
Status: Published in ApJ

Step 1: Understanding How to Carve Your Debris Disk

Let’s start with our solar system: the Kuiper belt, a large ring of icy asteroids, is believed to have been sculpted into its current shape by Neptune. Neptune may have previously scattered objects in the Kuiper Belt through gravitational interactions, but some of them (like Pluto) remain in an orbital resonance with Neptune. In the same way that Neptune shapes the Kuiper Belt, today’s authors believe a planet could be shaping an exo-Kuiper Belt around the star Fomalhaut.
.
What on Neptune is an orbital resonance, though? A planet orbiting a star has an orbital period, and the gravitational forces between nearby (astronomically speaking) objects can push these objects into a state where their orbital periods are multiples of each other. For example, Pluto and Neptune have a 2:3 orbital resonance, meaning Pluto completes two orbits for every three that Neptune does. The same can happen for the asteroids and planetesimals in the Kuiper Belt, so the same should happen in other star systems!
.
Step 2: Make Your Observations

If we understand how debris disks carved by exoplanets look — and we think we do — then we should be able to infer the existence of exoplanets! Today’s authors have used observations from the Atacama Large Millimeter/submillimeter Array (ALMA) of the debris disk around Fomalhaut and made some very clever calculations. We’ve known about this disk for a while, which is why today’s authors have studied it with a new analysis technique they developed.

Planeteismals — basically big rocks from a few to hundreds of kilometers across — that orbit in this disk do so with a certain eccentricity, and typically things in the same orbit would have the same eccentricity. But today’s authors were clever — they checked if there was an eccentricity gradient, meaning the planetesimals’ eccentricities depend on their semi-major axis (i.e., the mean orbit radius); we would typically not expect any eccentricity gradient for bodies orbiting a star unperturbed. The authors discovered that the gradient for planetesimals around Fomalhaut is negative, which implies the presence of a planet when you look at the maths behind gravitational interactions between planets and planetesimals.

A negative eccentricity gradient means the planetesimals gather up at the point on the orbit farthest from the star (the apocenter), and since there are more planetesimals in that region, they appear brighter in the ALMA data (see Fig. 1 left); the ring also appears slightly wider. If the eccentricity gradient were positive, the same thing would happen at the point on the orbit closest to the star (the pericenter). The authors term this phenomenon the “eccentric velocity divergence.”


Figure 1: Left: The observed intensity of the Fomalhaut debris disk with ALMA. Middle: the authors’ model that fits the ALMA data the best. Right: The residual (data – model) between model and data. White means there is a close match to the data (which is better). Credit: Lovell et al. 2025


When the authors ran their eccentric velocity divergence calculations for the Fomalhaut disk model, they compared it to observations using a Markov Chain Monte Carlo algorithm.

Figure 1 shows their best-fitting model, which fits remarkably well, based on the residual (i.e., the difference between model and data) you can see on the right — including the slightly wider ring at the apocenter!

The authors tested other scenarios with different gradients and allowed for the planetesimals to oscillate their eccentricity around their orbit, but they didn’t find a better-fitting scenario.

Step 3: Find a Carving Planet

Okay, so those were the details. The authors investigated a few scenarios to see what could be causing the observed debris disk and its negative eccentricity gradient, as well as an intermediate ring sitting between the main disk and the star that recently was seen with JWST. The authors tested two scenarios: one where a planet sits between the rings and evacuates the nearby region, and another where a planet is interior to the inner ring and clears the gap through orbital resonances (kind of like Neptune!). An illustration can be seen in Figure 2.

Figure 2: Illustration of possible planet-based scenarios that could create the observed debris disk around Fomalhaut. One features a planet between the observed debris disk rings, and another is where the planet is interior to both and carves the gap with orbital resonances. Credit: J. Williams


A planet was previously thought to exist around Fomalhaut, but it is now accepted there is not one we can currently observe. The authors point out that the possible planet sculpting this debris disk could be the same planet we thought existed previously, but at a lower mass (1–16 Earth masses; almost a Neptune mass). We can’t observe a planet with these parameters yet, but maybe with future observing facilities!

Finally, the authors stress, however, that it might not be a planet causing the observed structure — it could instead be the gravity of the planetesimals in the disk. Unfortunately, existing models are not equipped to explore this scenario, which is why the authors are planning to develop tools to investigate this next.

Original astrobite edited by Sandy Chiu.




About the author, Joe Williams:

I’m a third-year PhD student at the University of Exeter in the UK, and I study protoplanetary discs — mainly the tiny dust grains and their ices! In my spare time, I’m a climber, crocheter, and reader of sci-fi and fantasy books. My favourite sci-fi series is The Expanse!



Editor’s Note: Astrobites is a graduate-student-run organization that digests astrophysical literature for undergraduate students. As part of the partnership between the AAS and astrobites, we occasionally repost astrobites content here at AAS Nova. We hope you enjoy this post from astrobites; the original can be viewed at astrobites.org.


Sunday, December 14, 2025

New study sheds light on Milky Way's mysterious chemical history

This image shows the gas disc in a computer simulation of a Milky Way-like galaxy from the Auriga suite. Colours represent the ratio of magnesium (Mg) to iron (Fe), revealing that the galactic centre (pink) is poor in Mg, while the outskirts (green) are Mg-rich. These chemical patterns provide important clues about how the galaxy formed. Credit: Matthew D. A. Orkney (ICCUB-IEEC) /Auriga project.
Licence type:Attribution (CC BY 4.0)



Clues about how galaxies like our Milky Way form and evolve and why their stars show surprising chemical patterns have been revealed by a new study.

The research, published today in Monthly Notices of the Royal Astronomical Society, explores the origins of a puzzling feature in the Milky Way: the presence of two distinct groups of stars with different chemical compositions, known as the "chemical bimodality".

When scientists study stars near the Sun, they find two main types based on their chemical makeup, specifically, the amounts of iron (Fe) and magnesium (Mg) they contain. These two groups form separate "sequences" in a chemical diagram, even though they overlap in metallicity (how rich they are in heavy elements like iron). This has long puzzled astronomers.

The new study led by researchers at the Institute of Cosmos Sciences of the University of Barcelona (ICCUB) and the Centre national de la recherche scientifique (CNRS) uses advanced computer simulations (called the Auriga simulations) to recreate the formation of galaxies like the Milky Way in a virtual universe. By analysing 30 simulated galaxies, the team looked for clues about how these chemical sequences form.

Understanding the chemical history of the Milky Way helps scientists piece together how our gaaxy, and others like it, came to be. This includes our sister galaxy, Andromeda, in which no bimodality has yet been detected. It also provides clues about the conditions in the early universe and the role of cosmic gas flows and galaxy mergers.

"This study shows that the Milky Way's chemical structure is not a universal blueprint," said lead author Matthew Orkney, a researcher at ICCUB and the Institut d’Estudis Espacials de Catalunya (IEEC).

"Galaxies can follow different paths to reach similar outcomes, and that diversity is key to understanding galaxy evolution."

The study reveals that galaxies like the Milky Way can develop two distinct chemical sequences through various mechanisms. In some cases, this bimodality arises from bursts of star formation followed by periods of little activity, while in others it results from changes in the inflow of gas from the galaxy's surroundings.

Contrary to previous assumptions, the collision with a smaller galaxy known as Gaia-Sausage-Enceladus (GSE) is not a necessary condition for this chemical pattern to emerge. Instead, the simulations show that metal-poor gas from the circumgalactic medium (CGM) plays a crucial role in forming the second sequence of stars.

Moreover, the shape of these chemical sequences is closely linked to the galaxy's star formation history.

As new telescopes like the James Webb Space Telescope (JWST) and upcoming missions such as PLATO and Chronos provide more detailed data on stars and galaxies, researchers will be able to test these findings and refine our picture of the cosmos.

"This study predicts that other galaxies should exhibit a diversity of chemical sequences. This will soon be probed in the era of 30m telescopes where such studies in external galaxies will become routine," said Dr Chervin Laporte, of ICCUB-IEEC, CNRS-Observatoire de Paris and Kavli IPMU.

"Ultimately, these will also help us further refine the physical evolutionary path of our own Milky Way."




Media Contacts:

Sam Tonkin
Royal Astronomical Society
Mob: +44 (0)7802 877 700

press@ras.ac.uk

Dr Robert Massey
Royal Astronomical Society
Mob: +44 (0)7802 877 699

press@ras.ac.uk



Science Contacts:

Matthew Orkney
University of Barcelona

m.d.a.orkney@gmail.com



Images & video

Milky Way-like galaxy simulation

Caption: Computer simulation of a Milky Way-like galaxy from the Auriga suite, cycling between views of the stars, the gas coloured by iron (Fe) abundance, and the gas coloured by magnesium (Mg) abundance. The galaxy has developed a large, flat gas disc that forms a thin disc of young and blue stars. The gas disc was thicker in earlier stages, producing an older and redder population of stars in a thicker stellar disc. A scale bar in the lower-left corner indicates the size of the galaxy. For comparison, the Sun lies about 8 kiloparsecs (kpc) from the centre of our own Milky Way. Credit: Matthew D. A. Orkney (ICCUB-IEEC) /Auriga project

Auriga suite still

Caption: This image shows the gas disc in a computer simulation of a Milky Way-like galaxy from the Auriga suite. Colours represent the ratio of magnesium (Mg) to iron (Fe), revealing that the galactic centre (pink) is poor in Mg, while the outskirts (green) are Mg-rich. These chemical patterns provide important clues about how the galaxy formed. Credit: Matthew D. A. Orkney (ICCUB-IEEC) /Auriga project.



Further information

The paper ‘The Milky Way in context: The formation of galactic discs and chemical sequences from a cosmological perspective’ by M. D. A. Orkney et al. has been published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/staf1551.

This research has been led by researchers from the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), the Institute of Space Studies of Catalonia (IEEC) and the CNRS with the collaboration of scientists from Liverpool John Moores University and the Max-Planck-Institut für Astrophysik.



Notes for editors

About the Royal Astronomical Society

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The RAS organises scientific meetings, publishes international research and review journals, recognises outstanding achievements by the award of medals and prizes, maintains an extensive library, supports education through grants and outreach activities and represents UK astronomy nationally and internationally. Its more than 4,000 members (Fellows), a third based overseas, include scientific researchers in universities, observatories and laboratories as well as historians of astronomy and others.

The RAS accepts papers for its journals based on the principle of peer review, in which fellow experts on the editorial boards accept the paper as worth considering. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content.

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