Six billion tonnes a second: rogue planet Cha 1107-7626 found growing at record rate
Astronomers have identified an enormous ‘growth spurt’ in a so-called rogue planet. Unlike the planets in our Solar System, these objects do not orbit stars, free-floating on their own instead. The new observations, made with the European Southern Observatory’s Very Large Telescope (ESO’s VLT), reveal that this free-floating planet is eating up gas and dust from its surroundings at a rate of six billion tonnes a second. This is the strongest growth rate ever recorded for a rogue planet, or a planet of any kind, providing valuable insights into how they form and grow.
This artist’s impression shows Cha 1107-7626. Located about 620 light-years away, this rogue planet is about 5-10 times more massive than Jupiter and doesn’t orbit a star. It is eating up material from a disc around it and, using ESO’s Very Large Telescope (VLT), astronomers have discovered that it is now doing so at a rate of six billion tonnes per second –– the fastest ever found for any kind of planet. The team suspects that strong magnetic fields could be funnelling material towards the planet, something only seen in stars. When the infalling material reaches the planet it heats up its surface, creating a bright hot spot. The X-shooter spectrograph on ESO’s VLT detected a marked brightening in mid-2025, and found a clear fingerprint that this was caused by infalling gas. The observations show that the planet is now accreting matter about 8 times faster than a few months before. Credit: ESO/L. Calçada/M. Kornmesser
“People may think of planets as quiet and stable worlds, but with this discovery we see that planetary-mass objects freely floating in space can be exciting places,”
says Víctor Almendros-Abad, an astronomer at the Astronomical Observatory of Palermo, National Institute for Astrophysics (INAF), Italy and lead author of the new study.
The newly studied object, which has a mass five to 10 times the mass of Jupiter, is located about 620 light-years away in the constellation Chamaeleon. Officially named Cha 1107-7626, this rogue planet is still forming and is fed by a surrounding disc of gas and dust. This material constantly falls onto the free-floating planet, a process known as accretion. However, the team led by Almendros-Abad has now found that the rate at which the young planet is accreting is not steady.
This infrared image, taken with ESO’s Visible and Infrared Telescope for Astronomy (VISTA) shows the position in the sky of the rogue planet Cha 1107-7626. The planet is a dot located exactly at the centre of the frame. Credit: ESO/Meingast et al.
By August 2025, the planet was accreting about eight times faster than just a few months before, at a rate of six billion tonnes per second!
“This is the strongest accretion episode ever recorded for a planetary-mass object,”
says Almendros-Abad. The discovery, published today in The Astrophysical Journal Letters, was made with the X-shooter spectrograph on ESO’s VLT, located in Chile’s Atacama Desert. The team also used data from the James Webb Space Telescope, operated by the US, European and Canadian space agencies, and archival data from the SINFONI spectrograph on ESO’s VLT.
“The origin of rogue planets remains an open question: are they the lowest-mass objects formed like stars, or giant planets ejected from their birth systems?”
asks co-author Aleks Scholz, an astronomer at the University of St Andrews, United Kingdom. The findings indicate that at least some rogue planets may share a similar formation path to stars since similar bursts of accretion have been spotted in young stars before. As co-author Belinda Damian, also an astronomer at the University of St Andrews, explains:
“This discovery blurs the line between stars and planets and gives us a sneak peek into the earliest formation periods of rogue planets.”
By comparing the light emitted before and during the burst, astronomers gathered clues about the nature of the accretion process. Remarkably, magnetic activity appears to have played a role in driving the dramatic infall of mass, something that has only been observed in stars before. This suggests that even low-mass objects can possess strong magnetic fields capable of powering such accretion events. The team also found that the chemistry of the disc around the planet changed during the accretion episode, with water vapour being detected during it but not before. This phenomenon had been spotted in stars but never in a planet of any kind.
This visible-light image, part of the Digitized Sky Survey 2, shows the position in the sky of the rogue planet Cha 1107-7626. The planet (not visible here) is located exactly at the centre of the frame. Credit: ESO/ Digitized Sky Survey 2
Free-floating planets are difficult to detect, as they are very faint, but ESO’s upcoming Extremely Large Telescope (ELT), operating under the world’s darkest skies for astronomy, could change that. Its powerful instruments and giant main mirror will enable astronomers to uncover and study more of these lonely planets, helping them to better understand how star-like they are. As co-author and ESO astronomer Amelia Bayo puts it:
“The idea that a planetary object can behave like a star is awe-inspiring and invites us to wonder what worlds beyond our own could be like during their nascent stages.”
More information
This research was presented in a paper titled “Discovery of an Accretion Burst in a Free-Floating Planetary-Mass Object” to appear in The Astrophysical Journal Letters (doi:10.3847/2041-8213/ae09a8).
The team is composed of V. Almendros-Abad (Istituto Nazionale di Astrofisica – Osservatorio Astronomico di Palermo, Italy), Aleks Scholz (School of Physics & Astronomy, University of St Andrews, United Kingdom [St Andrews]), Belinda Damian (St Andrews), Ray Jayawardhana (Department of Physics & Astronomy, Johns Hopkins University, USA [JHU]), Amelia Bayo (European Southern Observatory, Germany), Laura Flagg (JHU), Koraljka Mužić (Instituto de Astrofísica e Ciências do Espaço, Faculdade de Ciências, Universidade de Lisboa, Portugal), Antonella Natta (School of Cosmic Physics, Dublin Institute for Advanced Studies and University College Dublin, Ireland) Paola Pinilla (Mullard Space Science Laboratory, University College London, UK) and Leonardo Testi (Dipartimento di Fisica e Astronomia, Università di Bologna, Italy).
Webb studies moon-forming disc around massive planet CT Cha B
The disc offers insight into how the moons of solar system gas giants like Jupiter might have formed.
The NASA/ESA/CSA James Webb Space Telescope has provided the first direct measurements of the chemical and physical properties of a potential moon-forming disc encircling a large exoplanet. The carbon-rich disc surrounding the world called CT Cha B, which is located 625 light years away from Earth, is a possible construction yard for moons, although no moons are detected in the Webb data.
Our Solar System contains eight major planets, and more than 400 known moons orbiting six of these planets. Where did they all come from? There are multiple formation mechanisms. The case for large moons, like the four Galilean satellites around Jupiter, is that they condensed out of a dust and gas disc encircling the planet when it formed. But that would have happened over 4 billion years ago, and there is scant forensic evidence today.
Webb has now provided the first direct view of material in a disc around a large exoplanet. An international team of astronomers have uncovered a carbon-rich disc encircling the world called CT Cha b, which is located 625 light-years away from Earth.
The young star the planet orbits is only 2 million years old and still accreting circumstellar material. However, the circumplanetary disc discovered by Webb is not part of the larger accretion disc around the central star. The two objects are 74 billion kilometres apart.
Observing planet and moon formation is fundamental to understanding the evolution of planetary systems across our galaxy. Moons likely outnumber planets, and some might be habitats for life as we know it. But we are now only entering an era where we can witness their formation.
This discovery fosters a better understanding of planet and moon formation, say researchers. Webb’s data is invaluable for making comparisons to our Solar System’s birth over 4 billion years ago.
“We can see evidence of the disc around the companion, and we can study the chemistry for the first time. We’re not just witnessing moon formation – we’re also witnessing this planet’s formation,” said co-lead author Sierra Grant of the Carnegie Institution for Science in Washington, D.C., USA.
“We are seeing what material is accreting to build the planet and moons,” added main lead author Gabriele Cugno of the University of Zurich in Switzerland and member of the National Centre of Competence in Research PlanetS.
Dissecting starlight
Infrared observations of CT Cha b were made with Webb’s MIRI (Mid-Infrared Instrument) using its medium resolution spectrograph. An initial look into Webb’s archival data revealed signs of molecules within the circumplanetary disc, which motivated a deeper dive into the data. Because the planet’s faint signal is buried in the glare of the host star, the researchers had to disentangle the light of the star from the planet using high-contrast methods.
“We saw molecules at the location of the planet, and so we knew that there was stuff in there worth digging for and spending a year trying to tease out of the data. It really took a lot of perseverance,” said Grant.
Ultimately, the team discovered seven carbon-bearing molecules within the planet’s disc, including acetylene (C2H2) and benzene (C6H6). This carbon-rich chemistry is in stark contrast to the chemistry seen in the disc around the host star, where the researchers found water but no carbon. The difference between the two discs offers evidence for their rapid chemical evolution over only 2 million years.
Genesis of moons
A circumplanetary disc of debris has long been hypothesized as the birthplace of Jupiter’s four major moons. These Galilean satellites must have condensed out of such a flattened disc billions of years ago, as evident in their co-planar orbits about Jupiter. The two outermost Galilean moons, Ganymede and Callisto, are 50% water ice. But they presumably have rocky cores, perhaps made of carbon or silicon.
“We want to learn more about how our Solar System formed moons. This means that we need to look at other systems that are still under construction. We’re trying to understand how it all works,” said Cugno. “How do these moons come to be? What are the ingredients? What physical processes are at play, and over what timescales? Webb allows us to witness the drama of moon formation and investigate these questions observationally for the first time.”
In the coming year, the team will use Webb to perform a comprehensive survey of similar objects to better understand the diversity of physical and chemical properties in the discs around young planets.
The James Webb Space Telescope studies the potential moon-forming disc around the massive exoplanet CT Cha B. An artistic rendering of a dust and gas disc encircling the young exoplanet, CT Cha b, 625 light-years from Earth. Spectroscopic data from the NASA/ESA/CSA James Webb Space Telescope suggest the disc contains the raw materials for moon formation. The planet appears at lower right, while its host star and surrounding protoplanetary disc are visible in the background. Credit: NASA, ESA, CSA, STScI, G. Cugno (University of Zürich, NCCR PlanetS), S. Grant (Carnegie Institution for Science), J, Olmsted (STScI), L. Hustak (STScI)
Bibliographic information:
Gabriele Cugno and Sierra L. Grant 2025, ApJL991 L46, DOI: 10.3847/2041-8213/ae0290
Webb explores Sagittarius B2, the largest star-forming cloud in the Milky Way
The NASA/ESA/CSA James Webb Space Telescope has revealed a colourful array of massive stars and glowing cosmic dust in the Sagittarius B2 (Sgr B2) molecular cloud, the most massive and active star-forming region in our Milky Way galaxy.
Stars, gas and cosmic dust in the Sagittarius B2 molecular cloud glow in near-infrared light, captured by Webb’s NIRCam (Near-Infrared Camera). In this light, astronomers see more of the region’s diverse, colourful stars, but less of its gas and dust structure. Webb’s instruments each provide astronomers with important information that help build a more complete picture of what is happening in this intriguing portion of the centre of our galaxy. Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI)
Sagittarius B2 is the Milky Way galaxy’s most massive and active star forming cloud, producing half of the stars created in the galactic centre region despite having only 10 percent of the area’s star-making material. Now, Webb has revealed stunning new views of the region, using both its near-infrared and mid-infrared instruments, to capture both its colourful stars and gaseous stellar nurseries in unprecedented detail.
Sagittarius B2 is located only a few hundred light-years from the supermassive black hole at the heart of the galaxy called Sagittarius A*, a region densely packed with stars, star-forming clouds, and complex magnetic fields. The infrared light that Webb detects is able to pass through some of the area’s thick clouds to reveal young stars and the warm dust surrounding them. Astronomers think that analysis of Webb’s data will help unravel enduring mysteries of the star formation process, and why Sagittarius B2 is forming so many more stars than the rest of the galactic centre.
However, one of the most notable aspects of Webb’s images of Sagittarius B2 are the portions that remain dark. These ironically empty-looking areas of space are actually so dense with gas and dust that even Webb cannot see through them. These thick clouds are the raw material of future stars and a cocoon for those still too young to shine.
Webb’s MIRI (Mid-Infrared Instrument) shows the Sagittarius B2 (Sgr B2) region in mid-infrared light, with warm dust glowing brightly. To the right is one clump of clouds that captured astronomers’ attention. It is redder than the rest of the clouds in the image and corresponds to an area that other telescopes have shown to be one of the most molecularly rich regions known. Additional analysis of this intriguing region could yield important insights into why Sgr B2 is so much more productive in making stars than the rest of the galactic centre. Only the brightest stars in this region emit mid-infrared light that can be picked up by Webb’s MIRI instrument, which is why this image has so many fewer stars than that captured by Webb’s NIRCam (Near-Infrared Camera). The darkest areas of the image are not empty space but areas where cosmic dust and gas are so dense that light cannot penetrate them to reach the telescope. Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI)
The high resolution and mid-infrared sensitivity of Webb’s MIRI (Mid-Infrared Instrument) revealed this region in unprecedented detail, including glowing cosmic dust heated by very young massive stars. The reddest area, known as Sagittarius B2 North, (note: north is to the right in these Webb images) is one of the most molecularly rich regions known, but astronomers have never seen it with such clarity.
This image of the Sagittarius B2 (Sgr B2) molecular cloud, captured by Webb’s MIRI (Mid-Infrared Instrument) includes compass arrows, scale bar, and colour key for reference. To create this image, mid-infrared wavelengths of light have been translated into visible-light colours. The colour key at the bottom shows which MIRI filters were used, and which visible-light colour was assigned to that filter. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI)
The difference longer wavelengths of light make, even within the infrared spectrum, are stark when comparing the images from Webb’s MIRI and NIRCam (Near-Infrared Camera) instruments. Glowing gas and dust appear dramatically in mid-infrared light, while all but the brightest stars disappear from view.
In contrast to MIRI, colourful stars steal the show in Webb’s NIRCam image, punctuated occasionally by bright clouds of gas and dust. Further research into these stars will reveal details of their masses and ages, which will help astronomers better understand the process of star formation in this dense, active galactic centre region. Has it been going on for millions of years? Or has some unknown process triggered it only recently?
This image of the Sagittarius B2 (Sgr B2) molecular cloud, captured by Webb’s NIRCam (Near-Infrared Camera) instrument includes compass arrows, scale bar, and colour key for reference. To create this image, near-infrared wavelengths of light have been translated into visible-light colours. The colour key at the bottom shows which NIRCam filters were used, and which visible-light colour was assigned to that filter. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped relative to direction arrows on a map of the ground (as seen from above). Credit: NASA, ESA, CSA, STScI, A. Ginsburg (University of Florida), N. Budaiev (University of Florida), T. Yoo (University of Florida). Image processing: A. Pagan (STScI)
Astronomers hope Webb will shed light on why star formation in the galactic centre is so disproportionate. Though the region is stocked with plenty of gaseous raw material, on the whole it is not nearly as productive as Sagittarius B2. While Sagittarius B2 has only 10 percent of the galactic centre’s gas, it produces 50 percent of its stars.
Bibliographic information:
Nazar Budaiev, Adam Ginsburg, Ashley T. Barnes, Desmond Jeff, Taehwa Yoo, Cara Battersby, Alyssa Bulatek, Xing Lu, Elisabeth A.C. Mills, Daniel L. Walker, JWST’s first view of the most vigorously star-forming cloud in the Galactic center — Sagittarius B2, DOI: https://doi.org/10.48550/arXiv.2509.11771
Hubble sees white dwarf eating piece of Pluto-like object: a new study reports the accretion of an icy extrasolar planetesimal on to WD 1647+375
In our nearby stellar neighbourhood, a burned-out star is snacking on a fragment of a Pluto-like object. With its unique ultraviolet capability, only the NASA/ESA Hubble Space Telescope could identify that this meal is taking place.
The stellar remnant is a white dwarf about half the mass of our Sun, but that is densely packed into a body about the size of Earth. Scientists think the dwarf’s immense gravity pulled in and tore apart an icy Pluto analogue from the system’s own version of the Kuiper Belt, an icy ring of debris that encircles our Solar System. The findings were reported on 18 September 2025 in the Monthly Notices of the Royal Astronomical Society.
An international team of astronomers were able to determine this carnage by analysing the chemical composition of the doomed object as its pieces fell onto the white dwarf. In particular, they detected “volatiles” (substances with low boiling points) including carbon, sulphur, nitrogen, and a high oxygen content that suggests the strong presence of water.
“We were surprised,” said Snehalata Sahu of the University of Warwick in the United Kingdom. Sahu led the data analysis of a Hubble survey of white dwarfs. “We did not expect to find water or other icy content. This is because the comets and Kuiper Belt-like objects are thrown out of their planetary systems early, as their stars evolve into white dwarfs. But here, we are detecting this very volatile-rich material. This is surprising for astronomers studying white dwarfs as well as exoplanets, planets outside our Solar System.”
Only with Hubble
Using Hubble’s Cosmic Origins Spectrograph, the team found that the fragments were composed of nearly two thirds water ice. The fact that they detected so much ice meant that the pieces were part of a very massive object that formed far out in the star system’s icy Kuiper Belt analogue. Using Hubble data, scientists calculated that the object was bigger than typical comets and may be a fragment of an exo-Pluto.
They also detected a large fraction of nitrogen – the highest ever detected in white dwarf debris systems.
“We know that Pluto’s surface is covered with nitrogen ices,” said Sahu. “We think that the white dwarf accreted fragments of the crust and mantle of a dwarf planet.”
Accretion of these volatile-rich objects by white dwarfs is very difficult to detect in visible light. These volatile elements can only be detected with Hubble’s unique ultraviolet light sensitivity. In optical light, the white dwarf would appear ordinary.
About 260 light-years away, the white dwarf is a relatively close cosmic neighbor. In the past, when it was a Sun-like star, it would have been expected to host planets and an analogue to our Kuiper Belt.
Like seeing our Sun in the future
Billions of years from now, when our Sun burns out and collapses to a white dwarf, Kuiper Belt objects will be pulled in by the stellar remnant’s immense gravity.
“These planetesimals will then be disrupted and accreted,” said Sahu. “If an alien observer looks into our Solar System in the far future, they might see the same kind of remains we see today around this white dwarf.”
The team hopes to use the NASA/ESA/CSA James Webb Space Telescope to detect molecular features of volatiles such as water vapour and carbonates by observing this white dwarf in infrared light. By further studying white dwarfs, scientists can better understand the frequency and composition of these volatile-rich accretion events.
Sahu is also following the recent discovery of the interstellar comet 3I/ATLAS. She is eager to learn its chemical composition, especially its fraction of water.
“These types of studies will help us learn more about planet formation. They can also help us understand how water is delivered to rocky planets,” said Sahu.
Boris Gänsicke, of the University of Warwick and a visitor at Spain’s Instituto de Astrofisica de Canarias, was the principal investigator of the Hubble program that led to this discovery.
“We observed over 500 white dwarfs with Hubble. We’ve already learned so much about the building blocks and fragments of planets, but I’ve been absolutely thrilled that we now identified a system that resembles the objects in the frigid outer edges of our solar system,” said Gänsicke. “Measuring the composition of an exo-Pluto is an important contribution toward our understanding of the formation and evolution of these bodies.”
Thanks to the Hubble Space Telescope, a new study reports the accretion of an icy extrasolar planetesimal on to white dwarf WD 1647+375. This artist’s concept shows a white dwarf surrounded by a large debris disc. Debris from pieces of a captured, Pluto-like object is falling onto the white dwarf. Credit: T. Pyle (Caltech, NASA’s Jet Propulsion Laboratory)
Bibliographic information:
Snehalata Sahu, Boris T Gänsicke, Jamie T Williams, Detlev G Koester, Jay Farihi, Steven J Desch, Nicola Pietro Gentile Fusillo, Dimitri Veras, Sean N Raymond, Maria Teresa Belmonte, Discovery of an icy and nitrogen-rich extrasolar planetesimal, Monthly Notices of the Royal Astronomical Society, Volume 543, Issue 1, October 2025, Pages 223–232, https://doi.org/10.1093/mnras/staf1424
LVK: ten years after the discovery, gravitational waves verify Stephen Hawking’s Black Hole Area Theorem
LIGO, Virgo and KAGRA celebrate the anniversary of the first gravitational waves detection and announce verification of Stephen Hawking’s Black Hole Area Theorem.
On September 14, 2015, a signal arrived on Earth, carrying information about a pair of remote black holes that had spiraled together and merged. The signal had traveled about 1.3 billion years to reach us at the speed of light—but it was not made of light. It was a different kind of signal: a quivering of space-time called gravitational waves, first predicted by Albert Einstein 100 years prior. On that day 10 years ago, the twin detectors of the Laser Interferometer Gravitational-Wave Observatory (LIGO) made the first-ever direct detection of gravitational waves. The LIGO and Virgo collaborations announced it to the world in February 2016, after six months of analysis and verification.
The historic discovery meant that researchers could now sense the universe through three different means. Light waves, such as X-rays, optical, radio, and other wavelengths of light, as well as high-energy particles called cosmic rays and neutrinos had been captured before, but this was the first time researchers had witnessed a cosmic event through its gravitational warping of space-time. For this achievement, first dreamed up more than 40 years prior, three of the LIGO founders won the 2017 Nobel Prize in Physics: MIT’s Rainer Weiss, professor of physics, emeritus (who recently passed away at age 92); Caltech’s Barry Barish; and Caltech’s Kip Thorne.
Ten Years of LVK Discoveries This chart plots discoveries made by the LIGO-Virgo-KAGRA (LVK) network since LIGO’s first detection, in 2015, of gravitational waves emanating from a pair of colliding black holes. The detections consist mainly of black hole mergers, but a handful involve neutron stars (either black hole-neutron star collisions or neutron star-neutron star collisions). So far, during the current, fourth science run, the LVK detectors have spotted about 220 mergers, which more than doubles the number (90) found in the first three runs combined. The closest event observed to date, shown in Run 2 and indicated by the down arrow, is a binary neutron star merger known as GW170817, located only 0.13 gigalight-years away (or 130 million light-years). In this chart, the total masses of the initial objects are represented by size, while the signal strength is indicated by color. The plot demonstrates that over time the gravitational-wave observatories are both finding more black holes and detecting them with higher signal-to-noise ratios, thanks to cutting-edge advancements made to the detectors. Note that the black hole detections in the latter half of the fourth run are grey and appear to be the same size because these data have not been released in full—with the exception of the event called GW250114. That event, the clearest signal heard by LIGO yet, appears as a bright, orange dot on the chart in the fourth run. Image credits: LIGO/Caltech/MIT/R. Hurt (IPAC)
LIGO, which consists of detectors in both Hanford, Washington and Livingston, Louisiana, the Virgo detector in Italy and KAGRA in Japan operate in coordination and currently are routinely observing roughly one black hole merger every three days. Together, the gravitational-wave-hunting network, known as LVK (LIGO, Virgo, KAGRA), has captured a total of more than 300 black hole mergers, most of which are already confirmed while others await further analysis. During the network’s current science run, the fourth since the first run in 2015, the LVK has discovered about 230 candidate black hole mergers, more than doubling the number caught in the first three runs.
The dramatic rise in the number of LVK discoveries over the past decade is owed to several improvements to their detectors—some of which involve cutting-edge quantum precision engineering. These gravitational-wave interferometers remain by far the most precise rulers for making measurements ever created by humans. The space-time distortions induced by gravitational waves are incredibly minuscule. To sense them, LIGO and Virgo must detect changes in space-time smaller than 1/10,000 the width of a proton. That’s 700 trillion times smaller than the width of a human hair.
The Clearest Signal Yet
The improved sensitivity of the instruments is exemplified in a recent discovery of a black hole merger referred to as GW250114 (the numbers denote the date the gravitational-wave signal arrived at Earth: January 14, 2025). The event was not that different from the first-ever detection (called GW150914)—both involve colliding black holes about 1.3 billion light-years away with masses between 30 to 40 times that of our Sun. But thanks to 10 years of technological advances reducing instrumental noise, the GW250114 signal is dramatically clearer.
“We can hear it loud and clear, and that lets us test the fundamental laws of physics,”
says LIGO team member Katerina Chatziioannou, Caltech assistant professor of physics and William H. Hurt Scholar, and one of the leading authors of a new study on GW250114 published in the Physical Review Letters.
By analyzing the frequencies of gravitational waves emitted by the merger, the LVK team was able to provide the best observational evidence captured to date for what is known as the black hole area theorem, an idea put forth by Stephen Hawking in 1971 that says the total surface areas of black holes cannot decrease. When black holes merge, their masses combine, increasing the surface area. But they also lose energy in the form of gravitational waves during the phenomenon. Additionally, the merger can cause the combined black hole to increase its spin, which leads to it having a smaller area. The black hole area theorem states that, despite these competing factors, the total surface area must grow in size.
Later, Hawking and physicist Jacob Bekenstein concluded that a black hole’s area is proportional to its entropy, or degree of disorder. The findings paved the way for later groundbreaking work in the field of quantum gravity, which attempts to unite two pillars of modern physics: general relativity and quantum physics.
Picture Credits: Lucy Reading-Ikkanda/Simons Foundation
In essence, the detection (made just by LIGO, since Virgo was undergoing routine maintenance and KAGRA was offline during this particular observation) allowed the team to “hear” two black holes growing as they merged into one, verifying Hawking’s theorem. The initial black holes had a total surface area of 240,000 square kilometers (roughly the size of United Kingdom), while the final area was about 400,000 square kilometers (almost the size of Sweden)—a clear increase. This is the second test of the black hole area theorem; an initial test was performed in 2021 using data from the first GW150914 signal, but because that data was not as clean, the results had a confidence level of 95 percent as compared to 99.999 percent for the new data. Kip Thorne recalls Hawking phoning him to ask whether LIGO might be able to test his theorem immediately after he learned of the 2015 gravitational-wave detection. Hawking died in 2018 and sadly did not live to see his theory observationally verified.
“If Hawking were alive, he would have reveled in seeing the area of the merged black holes increase,” Thorne says.
The trickiest part of this type of analysis had to do with determining the final surface area of the merged black hole. The surface areas of pre-merger black holes can be more readily gleaned as the pair spiral together, roiling space-time and producing gravitational waves. But after the black holes merge, the signal is not as clearcut. During this so-called ringdown phase, the final black hole vibrates like a struck bell.
Picture Credits: Lucy Reading-Ikkanda/Simons Foundation
In the new study, the researchers were able to precisely measure the details of the ringdown phase, which allowed them to calculate the mass and spin of the black hole, and subsequently determine its surface area. More precisely, they were able, for the first time, to confidently pick out two distinct gravitational-wave modes in the ringdown phase. The modes are like characteristic sounds a bell would make when struck; they have somewhat similar frequencies but die out at different rates, which makes them hard to identify. The improved data for GW250114 meant that the team could extract the modes, demonstrating that the black hole’s ringdown occurred exactly as predicted by math models Another study from the LVK, submitted to Physical Review Letters today, places limits on a predicted third, higher-pitch tone in the GW250114 signal, and performs some of the most stringent tests yet of general relativity’s accuracy in describing merging black holes.
“Analyzing strain data from the detectors to detect transient astrophysical signals, send out alerts to trigger follow-up observations from telescopes or publish physics results gathering information from up to hundreds of events is quite a long journey – adds Nicolas Arnaud, CNRS researcher in France and Virgo coordinator of the fourth science run – Out of the many skilled steps that such a complex framework requires, I see the humans behind all these data, in particular those who are on duty at any time, watching over our instruments. There are LVK scientists in all regions, pursuing a common goal: literally, the Sun never goes down above our collaborations!”
Pushing the limits
LIGO and Virgo have also unveiled neutron stars over the past decade. Like black holes, neutron stars form the explosive deaths of massive stars, but they weigh less and glow with light. Of note, in August of 2017, LIGO and Virgo witnessed an epic collision between a pair of neutron stars—a kilonova—that sent gold and other heavy elements flying into space and drew the gaze of dozens of telescopes around the world, which captured light ranging from high-energy gamma rays to low-energy radio waves. The “multi-messenger” astronomy event marked the first time that both light and gravitational waves had been captured in a single cosmic event. Today, the LVK continues to alert the astronomical community to potential neutron star collisions, who then use telescopes to search the skies for signs of another kilonova.
“The global LVK network is essential to gravitational-wave astronomy,” says Gianluca Gemme, Virgo spokesperson and director of research at INFN (Istituto Nazionale di Fisica Nucleare). “With three or more detectors operating in unison, we can pinpoint cosmic events with greater accuracy, extract richer astrophysical information, and enable rapid alerts for multi-messenger follow-up. Virgo is proud to contribute to this worldwide scientific endeavor.”
Other LVK scientific discoveries include the first detection of collisions between one neutron star and one black hole; asymmetrical mergers, in which one black hole is significantly more massive than its partner neutron star; the discovery of the lightest black holes known, challenging the idea that there is a “mass gap” between neutron stars and black holes; and the most massive black hole merger seen yet with a merged mass of 225 solar masses. For reference, the previous record-holder for the most massive merger had a combined mass of 140 solar masses.
In the coming years, the scientists of LVK hope to further fine tune their machines, expanding their reach deeper and deeper into space. They also plan to use the knowledge they have gained to build another gravitational-wave detector, LIGO India. Looking farther into the future, scientists are working on a concept for even larger detectors.The European project, called Einstein Telescope, plans to build one or two huge underground interferometers with arms of more than 10 kilometers, The US one, called Cosmic Explorer, would be similar to the current LIGO but with arms 40 kilometers long. Observatories on this scale would allow scientists to hear the earliest black hole mergers in the universe and, possibly, the echo of the gravitational shakes of the very first moments of our universe.
“This is an amazing time for gravitational wave research: thanks to instruments such as Virgo, LIGO and KAGRA, we can explore a dark universe that was previously completely inaccessible. – said Massimo Carpinelli, professor at University of Milano Bicocca and director of the European Gravitational Observatory in Cascina – The scientific achievements of these 10 years are triggering a real revolution in our view of the Universe. We are already preparing a new generation of detectors such as the Einstein Telescope in Europe and Cosmic Explorer in the US, as well as the LISA space interferometer, which will take us even further into space and back in time. In the coming years, we will certainly be able to tackle these extraordinary challenges thanks to increasingly broad and solid cooperation between scientists, different countries and institutions, both at European and global level.”
LVK: ten years after the discovery, gravitational waves verify Stephen Hawking’s Black Hole Area Theorem. A Cosmic Symphony Revealed. This artwork imagines the ultimate front-row seat for GW250114, a powerful collision between two black holes observed in gravitational waves by the US National Science Foundation LIGO. It depicts the view from one of the black holes as it spirals toward its cosmic partner. Ten years after LIGO’s landmark detection of gravitational waves, the observatory’s improved detectors allowed it to “hear” this celestial collision with unprecedented clarity. The gravitational-wave data enabled scientists to distinguish multiple subtle tones ringing out like a cosmic bell across the universe (imagined here as intertwining musical threads spiraling toward the center). Though only LIGO was online during GW250114, it now routinely operates as part of a network with other gravitational-wave detectors, including Europe’s Virgo and Japan’s KAGRA. Image credit: Aurore Simonnet (SSU/EdEon)/LVK/URI
Webb observes Sharpless 2-284, a Herbig-Haro object, an immense stellar jet on outskirts of our Milky Way
Way out toward the edge of our Milky Way galaxy, a young star that is still forming is sending out a birth announcement to the Universe in the form of a celebratory looking firework. These seething twin jets of hot gasses are blazing across 8 light-years – twice the distance between our Sun and the nearest star system. Superheated gases falling onto the massive star are blasted back into space along the star’s rotational axis and powerful magnetic fields confine the jets to narrow beams. The NASA/ESA/CSA James Webb Space Telescope witnessed the spectacle in infrared light. The jets are plowing into interstellar dust and gas, creating fascinating details captured only by Webb.
The NASA/ESA/CSA James Webb Space Telescope recently imaged an extremely large stellar jet at the outskirts of our Milky Way galaxy in the proto-cluster Sh2-284. This Herbig-Haro (HH) object, jets of plasma shooting out from newly formed stars, is 8 light-years across. This is about double the distance from our Sun to its closest neighboring star system, Alpha Centauri. Its detection provides evidence that HH jets scale with the mass of their parent stars—the more massive the stellar engine driving the plasma, the larger the resulting jet. Credit: NASA, ESA, CSA, STScI, Y. Cheng (NAOJ), J. DePasquale (STScI)
A blowtorch of seething gasses erupting from a volcanically growing monster star has been captured by Webb. Stretching across 8 light-years, the length of the stellar eruption is approximately twice the distance between our Sun and the nearby Alpha Centauri system. The size and strength of this particular stellar jet, known as Sharpless 2-284 (Sh2-284 for short), qualifies it as rare, say researchers.
The outflow is streaking across space at hundreds of thousands of kilometres per hour. The central protostar, weighing as much as ten of our Suns, is located 15,000 light-years away in the outer reaches of our galaxy.
The Webb discovery was serendipitous. “We didn’t really know there was a massive star with this kind of super-jet out there before the observation. Such a spectacular outflow of molecular hydrogen from a massive star is rare in other regions of our galaxy,” said lead author Yu Cheng of the National Astronomical Observatory of Japan.
This unique class of stellar fireworks, called Herbig-Haro (HH) objects, are highly collimated jets of plasma shooting out from newly forming stars. Such jetted outflows are a star’s spectacular “birth announcement” to the Universe. Some of the infalling gas building up around the central star is blasted along the star’s spin axis, likely under the influence of magnetic fields.
Today, well over 300 HH objects have been observed, but mainly from low-mass stars. These spindle-like jets offer clues into the nature of newly forming stars. The energetics, narrowness, and evolutionary time scales of HH objects all serve to constrain models of the environment and physical properties of the young stellar object powering the outflow.
“I was really surprised at the order, symmetry, and size of the jet when we first looked at it,” said co-author Jonathan Tan of the University of Virginia in Charlottesville and Chalmers University of Technology in Gothenburg, Sweden.
Its detection offers evidence that HH jets must scale up with the mass of the star powering them. The more massive the stellar engine propelling the plasma, the larger the gusher’s size.
The jet’s detailed filamentary structure, captured by Webb’s crisp resolution in infrared light, is evidence the jet is plowing into interstellar dust and gas. This creates separate knots, bow shocks, and linear chains.
The tips of the jet, lying in opposite directions, encapsulate the history of the star’s formation. “Originally the material was close into the star, but over 100,000 years the tips were propagating out, and then the stuff behind is a younger outflow,” said Tan.
Outlier
At nearly twice the distance from the galactic center as our Sun, the host proto-cluster that’s home to the voracious jet is on the periphery of our Milky Way galaxy.
Within the cluster, a few hundred stars are still forming. Being in the galactic hinterlands means the stars are deficient in heavier elements beyond hydrogen and helium. This is measured as metallicity, which gradually increases over cosmic time as each passing stellar generation expels end products of nuclear fusion through winds and supernovae. The low metallicity of Sh2-284 is a reflection of its relatively pristine nature, making it a local analog for the environments in the early universe that were also deficient in heavier elements.
“Webb’s exquisite data have also shown us that relatively more stars seem to form at lower masses in Sh2-284 than in closer, more metal-rich clusters,” said co-author Morten Andersen, of the European Southern Observatory, and lead author of a second paper on the Webb data. “This cluster is an excellent region to help us understand star formation throughout the Universe.”
“Massive stars, like the one found inside this cluster, have very important influences on the evolution of galaxies. Our discovery is shedding light on the formation mechanism of massive stars in low metallicity environments, so we can use this massive star as a laboratory to study what was going on in earlier cosmic history,” added Cheng.
Unrolling stellar tapestry
Stellar jets, which are powered by the gravitational energy released as a star grows in mass, encode the formation history of the protostar.
“Webb’s new images are telling us that the formation of massive stars in such environments could proceed via a relatively stable disc around the star that is expected in theoretical models of star formation known as core accretion,” said Tan. “Once we found a massive star launching these jets, we realised we could use the Webb observations to test theories of massive star formation. We developed new theoretical core accretion models that were fit to the data, to basically tell us what kind of star is in the center. These models imply that the star is about 10 times the mass of the Sun and is still growing and has been powering this outflow.”
For more than 30 years, astronomers have disagreed about how massive stars form. Some think a massive star requires a very chaotic process, called competitive accretion.
In the competitive accretion model, material falls in from many different directions so that the orientation of the disc changes over time. The outflow is launched perpendicularly, above and below the disc, and so would also appear to twist and turn in different directions.
“However, what we’ve seen here, because we’ve got the whole history – a tapestry of the story – is that the opposite sides of the jets are nearly 180 degrees apart from each other. That tells us that this central disc is held steady and validates a prediction of the core accretion theory,” said Tan.
Where there’s one massive star, there could be others in this outer frontier of the Milky Way. Other massive stars may not yet have reached the point of firing off Roman-candle-style outflows. Data from the Atacama Large Millimeter Array in Chile, also presented in this study, has found another dense stellar core that could be in an earlier stage of construction.
This image of the stellar jet in Sh2-284, captured by the NASA/ESA/CSA James Webb Space Telescope’s NIRCam (Near-Infrared Camera), shows compass arrows, scale bar, and color key for reference. The north and east compass arrows show the orientation of the image on the sky. Note that the relationship between north and east on the sky (as seen from below) is flipped to the direction arrows on a map of the ground (as seen from above). The scale bar is labeled in light-years, which is the distance that light travels in one Earth-year, and arcsec (It takes 1.1 years for light to travel a distance equal to the length of the scale bar.) One light-year is equal to about 5.88 trillion miles or 9.46 trillion kilometers. This image shows invisible near-infrared wavelengths of light that have been translated into visible-light colors. The color key shows which NIRCam filters were used when collecting the light. The color of each filter name is the visible light color used to represent the infrared light that passes through that filter. Credit: NASA, ESA, CSA, STScI, Y. Cheng (NAOJ), J. DePasquale (STScI)
This sparkling scene of star birth was captured by the NASA/ESA/CSA James Webb Space Telescope. What appears to be a craggy, starlit mountaintop kissed by wispy clouds is actually a cosmic dust-scape being eaten away by the blistering winds and radiation of nearby, massive, infant stars.
Called Pismis 24, this young star cluster resides in the core of the nearby Lobster Nebula, approximately 5,500 light-years from Earth in the constellation Scorpius. Home to a vibrant stellar nursery and one of the closest sites of massive star birth, Pismis 24 provides rare insight into large and massive stars. This region is one of the best places to explore the properties of hot young stars and how they evolve.
This sparkling scene of star birth was captured by the NASA/ESA/CSA James Webb Space Telescope. What appears to be a craggy, starlit mountaintop kissed by wispy clouds is actually a cosmic dust-scape being eaten away by the blistering winds and radiation of nearby, massive, infant stars. Called Pismis 24, this young star cluster resides in the core of the nearby Lobster Nebula, approximately 5,500 light-years from Earth in the constellation Scorpius. Home to a vibrant stellar nursery and one of the closest sites of massive star birth, Pismis 24 provides rare insight into large and massive stars. This region is one of the best places to explore the properties of hot young stars and how they evolve. Credit: NASA, ESA, CSA, and STScI, A. Pagan (STScI)
At the heart of this glittering cluster is the brilliant Pismis 24-1. It is at the centre of a clump of stars above the jagged orange peaks, and the tallest spire is pointing directly toward it. Pismis 24-1 appears as a gigantic single star, and it was once thought to be the most massive known stars. Scientists have since learned that it is composed of at least two stars, though they cannot be resolved in this image. At 74 and 66 solar masses, respectively, the two known stars are still among the most massive and luminous stars ever seen.
Captured in infrared light by Webb’s NIRCam (Near-Infrared Camera), this image reveals thousands of jewel-like stars of varying sizes and colors. The largest and most brilliant ones with the six-point diffraction spikes are the most massive stars in the cluster. Hundreds to thousands of smaller members of the cluster appear as white, yellow, and red, depending on their stellar type and the amount of dust enshrouding them. Webb also shows us tens of thousands of stars behind the cluster that are part of the Milky Way galaxy.
Super-hot, infant stars (some almost 8 times the temperature of the Sun) blast out scorching radiation and punishing winds that are sculpting a cavity into the wall of the star-forming nebula. That nebula extends far beyond NIRCam’s field of view. Only small portions of it are visible at the bottom and top right of the image. Streamers of hot, ionized gas flow off the ridges of the nebula, and wispy veils of gas and dust, illuminated by starlight, float around its towering peaks. Dramatic spires jut from the glowing wall of gas, resisting the relentless radiation and winds. They are like fingers pointing toward the hot, young stars that have sculpted them. The fierce forces shaping and compressing these spires cause new stars to form within them. The tallest spire spans about 5.4 light-years from its tip to the bottom of the image. More than 200 of our solar systems out to Neptune’s orbit could fit into the width its tip, which is 0.14 light-years. In this image, the color cyan indicates hot or ionised hydrogen gas being heated up by the massive young stars. Dust molecules similar to smoke here on Earth are represented in orange. Red signifies cooler, denser molecular hydrogen. The darker the red, the denser the gas. Black denotes the densest gas, which is not emitting light. The wispy white features are dust and gas that are scattering starlight.
This sparkling scene of star birth was captured by the NASA/ESA/CSA James Webb Space Telescope. What appears to be a craggy, starlit mountaintop kissed by wispy clouds is actually a cosmic dust-scape being eaten away by the blistering winds and radiation of nearby, massive, infant stars. Called Pismis 24, this young star cluster resides in the core of the nearby Lobster Nebula, approximately 5,500 light-years from Earth in the constellation Scorpius. Home to a vibrant stellar nursery and one of the closest sites of massive star birth, Pismis 24 provides rare insight into large and massive stars. This region is one of the best places to explore the properties of hot young stars and how they evolve. Credit: NASA, ESA, CSA, and STScI, A. Pagan (STScI)
Prebunking: preemptively debunking falsehoods about elections can rebuild people’s confidence in election integrity
Inoculating people against misinformation by preemptively sharing factual information – a strategy termed “prebunking” – can sucessfully restore confidence in elections, according to a new study analyzing recent national elections in the US and Brazil. Confidence in elections can also increase when political elites go against their own interests and actively debunk election falsehoods. John Carey and colleagues call this latter phenomenon “credible source corrections.”
Both Brazilian President Jair Bolsonaro and US President Donald Trump leveled false accusations about election fraud after losing their respective bids for reelection in 2020 and 2022, respectively, galvanizing their supporters to attempt democracy-threatening insurrections. These allegations persisted in the US throughout the country’s 2022 midterm elections.
Here, Carey et al. investigate the impact of two strategies to correct mistaken beliefs about elections’ credibility: prebunking and credible source corrections. The first introduces people to brief descriptions of circulating falsehoods and then disproves that misinformation with evidence, essentially vaccinating people against viral conspiracies. The second happens when sources whom already-misinformed people deem credible – typically those in the same political party as the leader who lost – defend election integrity by challenging the leader’s false narrative. The fact that these sources do so in opposition to their own political interests renders their statements more convincing.
To quantify the success of these tactics, Carey et al. conducted three studies. The first (involving 2,643 people) examined how prebunking and credible source corrections repaired election confidence before the 2022 US midterm elections. Participants interacted with factual short articles about the elections, short articles citing credible sources, or a placebo.
The second (involving 2,949 people) mirrored the first study’s methods, looking at the effects of prebunking and credible source corrections after Brazil’s 2022 presidential election. For both studies, prebunking was most successful in re-establishing election confidence. Credible source corrections also proved successful, but less consistently so.
In the third study (involving 2,030 people), the authors examined whether prebunking with a forewarning message that shared conspiracies worked better or worse than prebunking without it. This study focused on the 2022 US midterm elections and also considered expectations about the upcoming 2024 US general election. Prebunking without exposure to conspiracies was far more effective, likely because exposure induced skepticism toward subsequent factual articles. Notably, both tactics had the biggest impact on those who were already the most misinformed.
“Together, these approaches are practical, efficient, and scalable – key traits for real-world implementation by civil society groups, journalists, or election agencies,” Natalia Bueno suggests in a related Focus. “Equally promising is the fact that these strategies are relatively low-cost. Prebunking messages can be delivered in brief posts, using publicly available information.”
John M. Carey, Brian Fogarty, Marília Gehrke, Brendan Nyhan, Jason Reifler, Prebunking and credible source corrections increase election credibility: Evidence from the US and Brazil, Science Advances, DOI: 10.1126/sciadv.adv3758
Press release from the American Association for the Advancement of Science – AAAS, by Abigail Eisenstadt.
New fossils show how “bizarre” armoured dinosaur, Spicomellus afer, had 1 metre spikes sticking out from its neck
Research fossils show that the famous tail weapons of ankylosaurs evolved much earlier than previously thought
The world’s most unusual dinosaur is even stranger than first realised…
Today, research published in Nature reports that Spicomellus afer had a tail weapon more than 30 million years before any other ankylosaur, as well as a unique bony collar ringed with metre-long spikes sticking out from either side of its neck.
Spicomellus is the world’s oldest ankylosaur, having lived more than 165 million years ago in the Middle Jurassic near what is now the Moroccan town of Boulemane. It was the first ankylosaur to be found on the African continent.
The province Fes Meknes, within which the Boulemane Province has been located since 2015. Picture by Rherrad, CC BY-SA 4.0
New remains of Spicomellus found by a team of palaeontologists have helped to build upon the original description of the unusual animal. The initial description of the species was published in 2021 and was based on one rib bone. The team now know that the animal had bony spikes fused onto and projecting from all of its ribs, a feature not seen in any other vertebrate species living or extinct. It had long spikes, measuring 87 centimetres, which authors believe would have been even longer during the animal’s life, that emerged from a bony collar that sat around its neck.
Prof Susannah Maidment of Natural History Museum, London, and the University of Birmingham, who co-led the team of researchers said, “To find such elaborate armour in an early ankylosaur changes our understanding of how these dinosaurs evolved. It shows just how significant Africa’s dinosaurs are, and how important it is to improve our understanding of them.”
“Spicomellus had a diversity of plates and spikes extending from all over its body, including metre-long neck spikes, huge upwards-projecting spikes over the hips, and a whole range of long, blade-like spikes, pieces of armour made up of two long spikes, and plates down the shoulder. We’ve never seen anything like this in any animal before”
“It’s particularly strange as this is the oldest known ankylosaur, so we might expect that a later species might have inherited similar features, but they haven’t.”
Project co-lead, Professor Richard Butler of the University of Birmingham, said, “Seeing and studying the Spicomellus fossils for the first time was spine-tingling. We just couldn’t believe how weird it was and how unlike any other dinosaur, or indeed any other animal we know of alive or extinct. It turns much of what we thought we knew about ankylosaurs and their evolution on its head and demonstrates just how much there still is to learn about dinosaurs”.
Authors postulate that this array of spikes would have been used for attracting mates and showing off to rivals. Interestingly, similar display armour has not yet been found in any other ankylosaur, with later species possessing armour that probably functioned more for defence.
One explanation for this is that as larger predatory dinosaurs evolved in the Cretaceous, as well as bigger carnivorous mammals, crocodiles and snakes, the rising risk of predation could have driven ankylosaur armour to become simpler and more defensive.
One feature of early ankylosaurs that may have survived, however, is their tail weaponry. While the end of Spicomellus’ tail hasn’t been found, the bones that do survive suggest that it had a club or a similar tail weapon.
Some of the tail vertebrae are fused together to form a structure known as a handle, which has only been found in ankylosaurs with a tail club. However, all these animals lived millions of years later in the Cretaceous.
Authors of the study believe that the combination of a tail weapon and an armoured shield that protected the hips suggest that many of the ankylosaurs’ key adaptations already existed by the time of Spicomellus.
The discovery reinforces the importance of the fossil record in solving evolutionary puzzles and deepening our understanding of the geographic distribution of dinosaurs. It also helps to spark public imagination in dinosaurs as we learn more about the baffling characteristics of species like Spicomellus.
Professor Driss Ouarhache, lead of the Moroccan team from the Université Sidi Mohamed Ben Abdellah who co-developed the research, says, “This study is helping to drive forward Moroccan science. We’ve never seen dinosaurs like this before, and there’s still a lot more this region has to offer.”
The Spicomellus afer remains that form the basis of this study were cleaned and prepared at the Department of Geology of the Dhar El Mahraz Faculty of Sciences in Fez, Morocco, using scientific equipment provided by the University of Birmingham’s Research England International Strategy and Partnership Fund. The fossils are now catalogued and stored on this site.
The paper ‘Extreme armour in the world’s oldest ankylosaur’ is available now in Nature.
This research is part of the Natural History Museum’s Evolution of Life Research Theme that seeks to reveal the causes and consequences of evolutionary and environmental change, which is central to understanding life on Earth. It is also a contribution from the Earth Heritage Network at the University of Birmingham, which seeks to develop new ways to use palaeontological resources for the benefit of society.
Kostensuchus atrox: a crocodile-relative “hypercarnivore” from prehistoric Patagonia was 11.5ft long and weighed 250kg
Kostensuchus atrox was a top predator which lived just before the extinction of the dinosaurs, and likely chomped on them
Kostensuchus atrox – Mounted skeleton (reconstructed 3D print and painted). José Brusco, CC-BY 4.0
A newly-discovered species of a large, crocodile-relative predator has been described via a remarkably well-preserved fossil from Argentina, according to a study published August 27, 2025, in the open-access journal PLOS One by Fernando Novas from Museo Argentino de Ciencias Naturales “Bernardino Rivadavia”, Argentina, and colleagues.
The Chorrillo Formation formed around 70 million years ago, during the Maastrichtian age at the very end of the Cretaceous period. At this time, southern Patagonia was a warm, seasonally humid landscape of freshwater floodplains, home to creatures like dinosaurs, turtles, frogs, and various mammals.
The new fossil unearthed in this formation is largely intact, including a skull and jaws with visible details, as well as multiple bones from the body. This crocodile-like apex predator may have reached around 3.5 meters (11.5 feet) long and weighed around 250 kilograms (551 pounds), with a wide, powerful jaw and big teeth capable of devouring large prey — likely including medium-sized dinosaurs. The researchers named the species Kostensuchus atrox, referring to the Patagonian wind known in the Tehuelche native language as the Kosten and the Egyptian crocodile-headed god known as Souchos, with atrox meaning “fierce” or “harsh”.
Kostensuchus atrox – skull already prepared, freed from the rock. José Brusco, CC-BY 4.0
K. atrox itself is not a dinosaur, but rather a peirosaurid crocodyliform, an extinct group of reptiles related to modern crocodiles and alligators. This species is the second-largest predator known to scientists from the Maastrichtian Chorrillo Formation, and the researchers believe it was likely one of the top predators in the region. K. atrox is also the first crocodyliform fossil found in the Chorrillo Formation, and one of the most intact peirosaurid crocodyliforms ever found, giving scientists unique new insight into these prehistoricanimals and their ecosystem.
Kostensuchus atrox – life restauration, 3 meters long. Art by Gabriel Diaz Yanten. Gabriel Diaz Yanten, CC-BY 4.0
Author countries: Argentina, Portugal, Japan.
Funding: DP 9282-R-22 National Geographic Society https://www.nationalgeographic.org/society/ The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ISC Faperj E-26/200.998/2024 Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro https://www.faperj.br/ The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. ISC CNPq 303596/2016-3 Conselho Nacional de Desenvolvimento Científico e Tecnológico https://www.gov.br/cnpq/pt-br The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Bibliographic information:
Novas FE, Pol D, Agnolín FL, Carvalho IdS, Manabe M, Tsuihiji T, et al., A new large hypercarnivorous crocodyliform from the Maastrichtian of Southern Patagonia, Argentina, PLoS One (2025) 20(8): e0328561, DOI: https://doi.org/10.1371/journal.pone.0328561
