SPACE/COSMOS
Giant star laid bare: reveals birthplace of silicon and sulfur
Researchers led by Northwestern University and the Weizmann Institute have discovered a new type of supernova that offers a rare glimpse into the depths of massive stars and exposes hidden sites where heavy chemical elements are formed
Massive stars have a layered structure, similar to an onion. The outermost layers predominantly comprise the lightest elements; as the layers move inward, the elements become heavier and heavier until reaching the innermost iron core. This is the accepted theory, but observations of massive exploding stars – a phenomenon known as supernova – had until now typically revealed only strong signatures of light elements, such as hydrogen and helium. In a new study published today in Nature – and featured on the journal’s cover – an international team from Northwestern University, the Weizmann Institute of Science and other research institutions discovered a never-before-seen type of supernova: one that is rich in heavy elements such as silicon, sulfur and argon. The observations suggest that the massive star, dubbed SN2021yfj, had somehow lost its outer layers while still “alive.” This finding offers direct evidence of the long-theorized inner layered structure of stellar giants and provides an unprecedented glimpse inside a massive star’s deep interior moments before its explosive death.
Video showing an artist’s depiction of the most likely SN 2021yfj scenario. Near the end of its life, the dying star underwent two rare, extremely violent episodes, ejecting shells rich in silicon (gray), sulfur (yellow) and argon (purple). These massive shells collided with one another so violently as to create a particularly brilliant supernova that could be seen from a distance of 2.2 billion light years. Credit: Keck Observatory/Adam Makarenko
“This is the first time we have seen a star that was essentially stripped to the bone,” said lead author Dr. Steve Schulze, a former member of Prof. Avishay Gal-Yam’s team at the Weizmann Institute and currently a researcher at Northwestern University. “It shows us how stars are structured and proves that they can be completely stripped all the way down and still produce a brilliant explosion that we can observe from very, very far distances.”
A hot, burning onion
Despite their immense dimensions – they weigh in at 10 to 100 times heavier than our Sun -- massive stars collapse within a fraction of a second, but the bright light emitted in the explosion can usually be observed for several weeks. Schulze and colleagues discovered the flare of SN2021yfj in September 2021 using the Zwicky Transient Facility, a telescope located east of San Diego, California, and equipped with a wide-field camera to scan the entire visible night sky. After looking through the telescope’s data, Schulze spotted an extremely luminous object in a star-forming region located 2.2 billion light-years from Earth.
To gain more information about the mysterious object, the team wanted to obtain its spectrum, which breaks down dispersed light into component colors, each of which represents a different element. By analyzing a supernova’s spectrum, scientists can determine which elements are present in the explosion.
"As soon as I saw the data Dr. Schulze sent me, it was obvious we were witnessing something no one had ever seen before"
Although Schulze immediately leapt into action, the spectrum search hit multiple dead ends. Telescopes around the globe were either unavailable or could not see through the clouds to obtain a clear image. Ultimately, a colleague at University of California Berkeley managed to provide the required spectrum data. The researchers were amazed to discover that instead of helium, carbon, nitrogen and oxygen typically found in other stripped supernovae, the spectrum of SN2021yfj was dominated by strong signals of silicon, sulfur and argon. Nuclear fusion produces these heavier elements within a massive star’s deep interior during its final stages of life.
Although massive stars typically shed layers before exploding, other observations of “stripped stars” had revealed layers of helium or carbon and oxygen, exposed after the outer hydrogen envelope was lost. But astrophysicists had never glimpsed anything deeper than that, hinting that something extremely violent and extraordinary must have been at play. The SN2021yfj ejected far more material than scientists had previously seen, enabling the team to peer into its core deeper than ever, detecting heavier elements.
“Something very violent must have happened”
“This star lost most of the material that it produced throughout its lifetime,” Schulze said. “So we could only see the material formed during the months right before its explosion. Something very violent must have happened to cause that.”
“Exposure of such a deep inner core challenges current theories about how giant stars lose mass and shed their outer layers before exploding as supernovas,” explains Dr. Ofer Yaron, a staff scientist in Gal-Yam’s group and a leading expert on supernova databases.
(yellow) and argon (purple). Credit: Keck Observatory/Adam Makarenko
The scientists are currently exploring multiple scenarios, including interactions with a potential companion star, a massive pre-supernova eruption or even unusually strong stellar winds. But, most likely, the team posits this mysterious supernova is the result of a massive star literally tearing itself apart. As the star’s core squeezes inward under its own gravity, it becomes even hotter and denser. The extreme heat and density then reignite nuclear fusion with such incredible intensity that it causes a powerful burst of energy that pushes away the star’s outer layers. Moreover, the scientists hypothesize that the explosion may have been the result of a collision between one of the star’s pushed-out layers with another layer that had been pushed out earlier. For now, however, the precise cause of this phenomenon remains an open question.
“It’s always surprising – and deeply satisfying – to discover a completely new kind of physical phenomenon,” says Gal-Yam, whose research group in Weizmann’s Particle Physics and Astrophysics Department focuses on understanding how the elements are formed in the universe. “As soon as I saw the data Dr. Schulze sent me, it was obvious we were witnessing something no one had ever seen before.
“Once we identified the spectral signatures of silicon, sulfur and argon, it was clear this was a major step forward: Peering into the depths of a giant star helps us understand where the heavy elements come from. Every atom in our bodies and in the world around us was created somewhere in the universe and went through countless transformations over billions of years before arriving at its current place, so tracing its origin and the process that created it is incredibly difficult. Now it appears that the inner layers of giant stars are production sites for some of these important, relatively heavy elements.”
Science Numbers
More than 25,000 supernova events have been studied to date, but SN2021yfj is the first in which the light spectrum emitted in the explosion revealed evidence of heavy elements, indicating that this type of explosion is exceptionally rare.
Also participating in the study were Dr. Luc Dessart of Institut d’Astrophysique de Paris, CNRS-Sorbonne Université, Paris, France; Prof. Adam A. Miller of Northwestern University, Evanston, IL, USA; Prof. Stan E. Woosley of the University of California, Santa Cruz, CA, USA; Dr. Yi Yang of Tsinghua University, Beijing, China; Prof. Mattia Bulla of the University of Ferrara, Ferrara, Italy; Dr. Ping Chen, Dr. Ido Irani, Prof. Doron Kushnir, Prof. Eran Ofek, Dr. Nora L. Strothjohann, Prof. Eli Waxman and Erez A. Zimmerman of Weizmann’s Particle Physics and Astrophysics Department; Prof. Jesper Sollerman, Prof. Ragnhild Lunnan, Dr. Nikhil Sarin, Dr. Seán J. Brennan, Prof. Claes Fransson, Dr. Anjasha Gangopadhyay and Dr. Anders Jerkstrand of Stockholm University, Stockholm, Sweden; Prof. Alexei V. Filippenko, Dr. Thomas G. Brink, Dr. Yuhan Yao and Dr. WeiKang Zheng of University of California, Berkeley, CA, USA; K-Ryan Hinds, Dr. Daniel A. Perley and Dr. Conor M. B. Omand of Liverpool John Moores University, Liverpool, UK; Dr. Daichi Tsuna, Kaustav K. Das, Dr. Christoffer Fremling, Dr. Yu-Jing Qin, Dr. Yashvi Sharma, Dr. Lin Yan, Dr. Frank. J. Masci, Josiah Purdum, Avery Wold and Prof. Shrinivas R. Kulkarni of the California Institute of Technology, Pasadena, CA, USA; Dr. Rachel J. Bruch of Tel Aviv University, Tel Aviv, Israel; Prof. Suhail Dhawan of the University of Cambridge, Cambridge, UK; Prof. Nikola Kneževic´ of the University of Belgrade, Serbia; Prof. Keiichi Maeda of Kyoto University, Kyoto, Japan; Prof. Kate Maguire of Trinity College Dublin, Dublin, Ireland; Tawny Sit of Ohio State University, Columbus, OH, USA; Gokul P. Srinivasaragavan of the University of Maryland, College Park, MD, USA; Dr. Yuki Takei of Kyoto University and the University of Tokyo, Japan; Prof. Eric C. Bellm of the University of Washington, Seattle, WA, USA; Prof. Michael W. Coughlin of the University of Minnesota, Minneapolis, MN, USA; and Dr. Mickaël Rigault of Université Claude Bernard Lyon 1, Villeurbanne, France.
Prof. Avishay Gal Yam holds the Arlyn Imberman Professorial Chair and heads the André Deloro Institute for Space and Optics Research and the Center for Experimental Physics. His research is supported by the Norman E. Alexander Family M Foundation ULTRASAT Data Center Fund.
Journal
Nature
Article Title
Extremely stripped supernova reveals a silicon and sulfur formation site
Article Publication Date
20-Aug-2025
Scientists date the origin of Jupiter by studying the formation of “molten rock raindrops”
Ancient droplets in meteorites trace the history of planet formation.
image:
Round chondrules visible in a thin section of the Allende meteorite under microscopic view. Credit: Akira Miyake, Kyoto University
view moreCredit: Akira Miyake, Kyoto University
Four and a half billion years ago Jupiter rapidly grew to its massive size. Its powerful gravitational pull disrupted the orbits of small rocky and icy bodies similar to modern asteroids and comets, called planetesimals. This caused them to smash into each other at such high speeds that the rocks and dust they contained melted on impact and created floating molten rock droplets, or chondrules, that we find preserved in meteorites today.
Now, researchers at Nagoya University in Japan and the Italian National Institute for Astrophysics (INAF) have for the first time determined how these droplets formed and accurately dated the formation of Jupiter based on their findings. Their study, published in Scientific Reports, shows how the characteristics of chondrules, particularly their sizes and the rate at which they cooled in space, are determined by the water contained in the impacting planetesimals. This explains what we observe in meteorite samples and proves that chondrule formation was a result of planet formation.
Time capsules from 4.6 billion years ago
Chondrules, small spheres approximately 0.1-2 millimeters wide, were incorporated into asteroids as the solar system formed. Billions of years later, pieces of these asteroids would break off and fall to Earth as meteorites. How chondrules came to have their round shape has puzzled scientists for decades.
“When planetesimals collided with each other, water instantly vaporized into expanding steam. This acted like tiny explosions and broke apart the molten silicate rock into the tiny droplets we see in meteorites today,” co-lead author Professor Sin-iti Sirono from Nagoya University’s Graduate School of Earth and Environmental Sciences explained.
“Previous formation theories couldn’t explain chondrule characteristics without requiring very specific conditions, while this model requires conditions that naturally occurred in the early solar system when Jupiter was born.”
The researchers developed computer simulations of Jupiter's growth and tracked how its gravity caused high-speed collisions between rocky and water-rich planetesimals in the early solar system.
“We compared the characteristics and abundance of simulated chondrules to meteorite data and found that the model spontaneously generated realistic chondrules. The model also shows that chondrule production coincides with Jupiter’s intense accumulation of nebular gas to reach its massive size. As meteorite data tell us that peak chondrule formation took place 1.8 million years after the solar system began, this is also the time at which Jupiter was born,” Dr. Diego Turrini, co-lead author and senior researcher at the Italian National Institute for Astrophysics (INAF) said.
A new way to date when planets form
This study provides a clearer picture of how our solar system formed. However, the production of chondrules started by Jupiter's formation is too brief to explain why we find chondrules of many different ages in meteorites. The most likely explanation is that other giant planets like Saturn also triggered chondrule formation when they were born.
By studying chondrules of different ages, scientists can trace the birth order of the planets and understand how our solar system developed over time. The research also suggests that these violent planet formation processes may occur around other stars and offers insights into how other planetary systems developed.
The study, “Chondrule formation by collisions of planetesimals containing volatiles triggered by Jupiter's formation,” was published in the journal Scientific Reports, on August 25, 2025, at DOI: 10.1038/s41598-025-12643-x.
Funding information:
This work was supported by JSPS KAKENHI Grant Number 25K07383, by the Italian Space Agency through ASI-INAF contract 2016-23-H.0 and 2021-5-HH.0 and by the European Research Council via the Horizon 2020 Framework Programme ERC Synergy “ECOGAL” Project GA-855130.
Jupiter's gravity caused planetesimal collisions that melted rock into droplets dispersed by expanding water vapor.
Credit
Diego Turrini and Sin-iti Sirono
Round chondrules visible in a thin section of the Allende meteorite under microscopic view.
Credit
Akira Miyake, Kyoto University
Akira Miyake, Kyoto University
Journal
Scientific Reports
Method of Research
Computational simulation/modeling
Article Title
Chondrule formation by collisions of planetesimals containing volatiles triggered by Jupiter's formation
Article Publication Date
25-Aug-2025
Victor Tangermann
Mon, August 25, 2025
FUTURISM
The core of Jupiter, the largest planet in our solar system, has long been a source of mystery for astronomers: an object so unfathomably dense and hot that it defies comprehension.
Conventional theories have suggested for years that the gas giant's behemoth interior was formed following an enormous collision with an early planet.
The "giant impact" theory suggests that roughly half of Jupiter's core originated from the remains of such a planet, explaining what researchers believe to be its strange, "fuzzy" interior.
But now, as detailed in a new paper published in the journal Monthly Notices of the Royal Astronomical Society, an international team has found that the theory may not hold up after all, potentially undermining the way we understand Jupiter's formation.
In their research, the scientists attempted to explain Jupiter's gradual blend of hydrogen layers, as first observed by NASA's Juno spacecraft. Researchers have long butted their heads over how such a structure could've come to be.
By simulating the conditions during a planetary impact using a supercomputer, the researchers posed the question of whether Jupiter's "dilute core" is really the result of a massive collision.
Confusingly, none of their giant impact simulations, even under the most extreme circumstances, resulted in the gradual blends of gas that currently seem to make up the planet's core, undermining current impact theories.
Instead, they found that the resulting cloud of rock and ice core material would settle into distinct layers, not a gradual blend.
The research sheds new light — and controversy — on how one of the largest and most extreme structures in our solar system originally came to be.
They propose in their paper that Jupiter's core formed gradually as it attracted heavy and light elements over time, "as part of the extended formation and evolution of giant planets, rather than through extreme, low-likelihood giant impacts."
"It's fascinating to explore how a giant planet like Jupiter would respond to one of the most violent events a growing planet can experience," said Durham University planetary scientist and lead author Thomas Sandnes in a statement.
"We see in our simulations that this kind of impact literally shakes the planet to its core — just not in the right way to explain the interior of Jupiter that we see today," he added.
Intriguingly, scientists have discovered that our system's other gas giant, Saturn, the second-largest planet after Jupiter, may also have a similar dilute core.
"The fact that Saturn also has a dilute core strengthens the idea that these structures are not the result of rare, extremely high-energy impacts but instead form gradually during the long process of planetary growth and evolution," said University of Oslo researcher and coauthor Luis Teodoro in the statement.
The same findings could even apply to other gas giants orbiting distant stars, suggesting their cores have complex interiors as well.
"Giant impacts are a key part of many planets' histories, but they can't explain everything!" exclaimed coauthor and SETI Institute research scientist Jacob Kegerreis.
The NSF Inouye Solar Telescope delivers record-breaking images of solar flare, coronal loops
The NSF inouye solar telescope observes its first x-class solar flare and reveals the smallest coronal loops ever imaged
video:
A high-cadence, high-resolution movie of the flare captured by the Inouye Solar Telescope, sped up by 100x - both bright ribbons and dark overlying coronal loops are visible. The image is about 4 Earth-diameters on each side.
view moreCredit: NSF/NSO/AURA
MAUI, HI - AUGUST 25, 2025 — The highest-resolution images of a solar flare captured at the H-alpha wavelength (656.28 nm) may reshape how we understand the Sun’s magnetic architecture—and improve space weather forecasting. Using the U.S. National Science Foundation (NSF) Daniel K. Inouye Solar Telescope, built and operated by the NSF National Solar Observatory (NSO), astronomers captured dark coronal loop strands with unprecedented clarity during the decay phase of an X1.3-class flare on August 8, 2024, at 20:12 UT. The loops averaged 48.2 km in width—perhaps as thin as 21 km—the smallest coronal loops ever imaged. This marks a potential breakthrough in resolving the fundamental scale of solar coronal loops and pushing the limits of flare modeling into an entirely new realm.
Coronal loops are arches of plasma that follow the Sun’s magnetic field lines, often preceding solar flares that trigger sudden releases of energy associated with some of these magnetic field lines twisting and snapping. This burst of energy fuels solar storms that can impact Earth’s critical infrastructure. Astronomers at the Inouye observe sunlight at the H-alpha wavelength (656.28 nm) to view specific features of the Sun, revealing details not visible in other types of solar observations.
“This is the first time the Inouye Solar Telescope has ever observed an X-class flare,” says Cole Tamburri, the study’s lead author who is supported by the Inouye Solar Telescope Ambassador Program while completing his Ph.D. at the University of Colorado Boulder (CU). The program is funded by the NSF and is designed to support Ph.D. students as they create a well-networked cohort of early-career scientists at U.S. Universities, who will bring their expertise in Inouye data reduction and analysis to the broader solar community. “These flares are among the most energetic events our star produces, and we were fortunate to catch this one under perfect observing conditions.”
The team—which includes scientists from the NSO, the Laboratory for Atmospheric and Space Physics (LASP), the Cooperative Institute for Research in Environmental Sciences (CIRES), and CU—focused on the razor-thin magnetic field loops (hundreds of them) woven above the flare ribbons. On average, the loops measured about 48 km across, but some were right at the telescope’s resolution limit. “Before Inouye, we could only imagine what this scale looked like,” Tamburri explains. “Now we can see it directly. These are the smallest coronal loops ever imaged on the Sun.”
The Inouye’s Visible Broadband Imager (VBI) instrument, tuned to the H-alpha filter, can resolve features down to ~24 km. That is over two and a half times sharper than the next-best solar telescope, and it is that leap in resolution that made this discovery possible. “Knowing a telescope can theoretically do something is one thing,” Maria Kazachenko, a co-author in the study and NSO scientist, notes. “Actually watching it perform at that limit is exhilarating.”
While the original research plan involved studying chromospheric spectral line dynamics with the Inouye’s Visible Spectropolarimeter (ViSP) instrument, the VBI data revealed something unexpected treasures—ultra-fine coronal structures that can directly inform flare models built with complex radiative-hydrodynamic codes. “We went in looking for one thing and stumbled across something even more intriguing,” Kazachenko admits.
Theories have long suggested coronal loops could be anywhere from 10 to 100 km in width, but confirming this range observationally has been impossible—until now. “We’re finally peering into the spatial scales we’ve been speculating about for years,” says Tamburri. “This opens the door to studying not just their size, but their shapes, their evolution, and even the scales where magnetic reconnection—the engine behind flares—occurs.”
Perhaps most tantalizing is the idea that these loops might be elementary structures—the fundamental building blocks of flare architecture. “If that’s the case, we’re not just resolving bundles of loops; we’re resolving individual loops for the first time,” Tamburri adds. “It’s like going from seeing a forest to suddenly seeing every single tree.”
The imagery itself is breathtaking: dark, threadlike loops arching in a glowing arcade, bright flare ribbons etched in almost impossibly sharp relief—a compact triangular one near the center, and a sweeping arc-shaped one across the top. Even a casual viewer, Tamburri suggests, would immediately recognize the complexity. “It’s a landmark moment in solar science,” he concludes. “We’re finally seeing the Sun at the scales it works on.” Something made only possible by the NSF Daniel K. Inouye Solar Telescope’s unprecedented capabilities.
The paper describing this study, titled “Unveiling Unprecedented Fine Structure in Coronal Flare Loops with the DKIST,” is now available in The Astrophysical Journal Letters.
###
About the U.S. NSF National Solar Observatory
The mission of the NSF National Solar Observatory (NSO) is to advance knowledge of the Sun, both as an astronomical object and as the dominant external influence on Earth, by providing forefront observational opportunities to the research community.
NSO built and operates the world’s most extensive collection of ground-based optical and infrared solar telescopes and auxiliary instrumentation— including the NSF GONG network of six stations around the world, and the world’s largest solar telescope, the NSF Daniel K. Inouye Solar Telescope—allowing solar physicists to probe all aspects of the Sun, from the deep solar interior to the photosphere, chromosphere, the outer corona, and out into the interplanetary medium. These assets also provide data for heliospheric modeling, space weather forecasting, and stellar astrophysics research, putting our Sun in the context of other stars and their environments.
Besides the operation of cutting-edge facilities, the mission includes the continued development of advanced instrumentation both in-house and through partnerships, conducting solar research, and educational and public outreach. NSO is managed by the Association of Universities for Research in Astronomy, Inc. (AURA) under a cooperative agreement with NSF. For more information, visit nso.edu.
A high-resolution image of the flare from the Inouye Solar Telescope, taken on August 8, 2024, at 20:12 UT. The image is about 4 Earth-diameters on each side.
A high-resolution image of the flare from the Inouye Solar Telescope, taken on August 8, 2024, at 20:12 UT. The image is about 4 Earth-diameters on each side.
Labels of the different relevant regions of the image are added for clarity: flare ribbons (bright areas of energy release in the dense lower solar atmosphere) and an arcade of coronal loops (arcs of plasma outlining magnetic field lines that transport energy from the corona to the flare ribbons).
Labels of the different relevant regions of the image are added for clarity: flare ribbons (bright areas of energy release in the dense lower solar atmosphere) and an arcade of coronal loops (arcs of plasma outlining magnetic field lines that transport energy from the corona to the flare ribbons).
Credit
NSF/NSO/AURA
NSF/NSO/AURA
Journal
The Astrophysical Journal Letters
Article Title
Unveiling Unprecedented Fine Structure in Coronal Flare Loops with the DKIST
Article Publication Date
25-Aug-2025
Astronomers map stellar ‘polka dots’ using NASA’s Tess, Kepler
video:
This artist’s concept illustrates the varying brightness of star with a transiting planet and several star spots.
view moreCredit: NASA’s Goddard Space Flight Center
Scientists have devised a new method for mapping the spottiness of distant stars by using observations from NASA missions of orbiting planets crossing their stars’ faces. The model builds on a technique researchers have used for decades to study star spots.
By improving astronomers’ understanding of spotty stars, the new model — called StarryStarryProcess — can help discover more about planetary atmospheres and potential habitability using data from telescopes like NASA’s upcoming Pandora mission.
“Many of the models researchers use to analyze data from exoplanets, or worlds beyond our solar system, assume that stars are uniformly bright disks,” said Sabina Sagynbayeva, a graduate student at Stony Brook University in New York. “But we know just by looking at our own Sun that stars are more complicated than that. Modeling complexity can be difficult, but our approach gives astronomers an idea of how many spots a star might have, where they are located, and how bright or dark they are.”
A paper describing StarryStarryProcess, led by Sagynbayeva, published Monday, August 25, in The Astrophysical Journal.
NASA’s TESS (Transiting Exoplanet Survey Satellite) and now-retired Kepler Space Telescopewere designed to identify planets using transits, dips in stellar brightness caused when a planet passes in front of its star.
These measurements reveal how the star’s light varies with time during each transit, and astronomers can arrange them in a plot astronomers call a light curve. Typically, a transit light curve traces a smooth sweep down as the planet starts passing in front of the star’s face. It reaches a minimum brightness when the world is fully in front of the star and then rises smoothly as the planet exits and the transit ends.
By measuring the time between transits, scientists can determine how far the planet lies from its star and estimate its surface temperature. The amount of missing light from the star during a transit can reveal the planet’s size, which can hint at its composition.
Every now and then, though, a planet’s light curve appears more complicated, with smaller dips and peaks added to the main arc. Scientists think these represent dark surface features akin to sunspots seen on our own Sun — star spots.
The Sun’s total number of sunspots varies as it goes through its 11-year solar cycle. Scientists use them to determine and predict the progress of that cycle as well as outbreaks of solar activity that could affect us here on Earth.
Similarly, star spots are cool, dark, temporary patches on a stellar surface whose sizes and numbers change over time. Their variability impacts what astronomers can learn about transiting planets.
Scientists have previously analyzed transit light curves from exoplanets and their host stars to look at the smaller dips and peaks. This helps determine the host star’s properties, such as its overall level of spottiness, inclination angle of the planet’s orbit, the tilt of the star’s spin compared to our line of sight, and other factors. Sagynbayeva’s model uses light curves that include not only transit information, but also the rotation of the star itself to provide even more detailed information about these stellar properties.
“Knowing more about the star in turn helps us learn even more about the planet, like a feedback loop,” said co-author Brett Morris, a senior software engineer at the Space Telescope Science Institute in Baltimore. “For example, at cool enough temperatures, stars can have water vapor in their atmospheres. If we want to look for water in the atmospheres of planets around those stars — a key indicator of habitability — we better be very sure that we’re not confusing the two.”
To test their model, Sagynbayeva and her team looked at transits from a planet called TOI 3884 b, located around 141 light-years away in the northern constellation Virgo.
Discovered by TESS in 2022, astronomers think the planet is a gas giant about five times bigger than Earth and 32 times its mass.
The StarryStarryProcess analysis suggests that the planet’s cool, dim star — called TOI 3384 — has concentrations of spots at its north pole, which also tips toward Earth so that the planet passes over the pole from our perspective.
Currently, the only available data sets that can be fit by Sagynbayeva’s model are in visible light, which excludes infrared observations taken by NASA’s James Webb Space Telescope. But NASA’s upcoming Pandora mission will benefit from tools like this one. Pandora, a small satellite developed through NASA’s Astrophysics Pioneers Program, will study the atmospheres of exoplanets and the activity of their host stars with long-duration multiwavelength observations. The Pandora mission’s goal is to determine how the properties of a star’s light differs when it passes through a planet’s atmosphere so scientists can better measure those atmospheres using Webb and other missions.
“The TESS satellite has discovered thousands of planets since it launched in 2018,” said Allison Youngblood, TESS project scientist at NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “While Pandora will study about 20 worlds, it will advance our ability to pick out which signals come from stars and which come from planets. The more we understand the individual parts of a planetary system, the better we understand the whole — and our own.”
Journal
The Astrophysical Journal
Article Title
Polka-dotted Stars: A Hierarchical Model for Mapping Stellar Surfaces Using Occultation Light Curves and the Case of TOI-3884
Article Publication Date
25-Aug-2025
New model aims to demystify ‘steam worlds’ beyond our solar system
Water-rich exoplanets known as sub-Neptunes may indicate where life exists elsewhere in the universe
video:
Animation of a steam world’s evolution from formation to very old age (100 million years to 20 billion years). The interior is initially hot, and cools over time. How fast the planet cools is determined by a complex interplay between the interior and the atmosphere.
view moreCredit: Credit: Astrobiology at UC Santa Cruz
For astrobiologists, the search for life beyond our solar system could be likened to where one would look in a vast desert—essentially, where there's water. And it turns out that one of the most common types of exoplanet observed in planetary systems beyond ours have a size and mass that indicate a water-rich interior. They are categorized as "sub-Neptunes" because their size and mass are between that of Earth and Neptune.
But because these types of exoplanets tend to be much closer to their host star than Earth is to the Sun, sub-Neptunes are too hot to have liquid water on their surface and support life. Instead, they would have atmospheres made of steam, over layers of an exotic phase of water that behaves like neither gas nor liquid. Since the existence of these "steam worlds" were first predicted 20 years ago, interest in their exact makeup and evolution has grown.
Now, astrobiologists and astronomers at the University of California, Santa Cruz, have developed a more precise way to model these steam worlds to help better understand their composition, and ultimately, how they formed in the first place. "When we understand how the most commonly observed planets in the universe form, we can shift our focus to less common exoplanets that could actually be habitable," said Artem Aguichine, a postdoctoral researcher at UC Santa Cruz who led the development of the new model.
The work is explained in a paper published on July 24 in The Astrophysical Journal and is co-authored by Professor Natalie Batalha, head of UC Santa Cruz's astrobiology initiative, along with Professor Jonathan Fortney, chair of the university's Astronomy and Astrophysics Department.
More than icy moons
For the first time in history, the James Webb Space Telescope (JWST) confirmed the presence of steam on a handful of sub-Neptunes. Astronomers expect JWST to observe dozens more, which is why such models are critical to connect what we see from the exoplanet’s surface to what is inside of them.
The models historically used to characterize sub-Neptunes were developed to study the icy moons in our solar system, such as Jupiter’s moon Europa and Saturn’s moon Enceladus. Aguichine says sophisticated models can help interpret what space telescopes like JWST reveal about sub-Neptunes.
Icy moons are small, condensed bodies with layered structures: icy crusts over liquid water oceans. Sub-Neptunes are much different. They are vastly more massive—10 to 100 times as much—and, again, they orbit much closer to their stars. So they don’t have icy crusts and liquid oceans like Europa or Enceladus. Instead, they develop thick steam atmospheres and layers of "supercritical water."
This exotic, supercritical phase of water has been recreated and studied in laboratories on Earth, exhibiting behavior that is far more complex than simple liquid water or ice—thus, making it difficult to model accurately. Some models even suggest that, under extreme pressure and temperature conditions inside sub-Neptunes, water may even transform into "superionic ice," a phase in which water molecules reorganize so hydrogen ions move freely through an oxygen lattice.
Neptune, and potentially sub-Neptunes as well. So, to model sub-Neptunes, researchers need to understand how water behaves as pure steam, as supercritical fluid, and in extreme states like superionic ice. This team's model accounts for the experimental data on the physics of water under extreme conditions and advances the theoretical modeling that's required.
“The interiors of planets are natural ‘laboratories’ for studying conditions that are difficult to reproduce in a university laboratory on Earth. What we learn could have unforeseen applications we haven’t even considered. The water worlds are especially exotic in this sense,” Batalha explained. “In the future, we may find that a subset of these water worlds represent new niches for life in the galaxy.”
By modeling the distribution of water in these common exoplanets, scientists can trace how water—one of the universe’s most abundant molecules—moves during the formation of planetary systems. Indeed, Aguichine said water has a range of fascinating properties:
- It is both a chemical acid and base, participating in chemical balance
- It is good at dissolving salts, sugars, and amino acids
- It creates hydrogen bonds – giving water a higher viscosity, a higher boiling point, a greater capacity to store heat, and more.
"Life can be understood as complexity,” Aguichine said, “and water has a wide range of properties that enables this complexity."
Looking back and forward
He also stressed that their modeling focuses not on static snapshots of sub-Neptunes, but accounts for their evolution over millions and billions of years. Because planetary properties change significantly over time, modeling that evolution is essential for accurate predictions, he said.
The modelling will soon be put to the test by continued observations with JWST, and also with future missions such as the European Space Agency's upcoming launch of the PLAnetary Transit and Oscillation (PLATO) of stars telescope, a mission designed to find Earth-like planets in the habitable zone of their host star.
"PLATO will be able to tell us how accurate our models are, and in what direction we need to refine them," Aguichine said. "So really, our models are currently making these predictions for the telescopes, while helping shape the next steps in the search for life beyond Earth."
Journal
The Astrophysical Journal
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Evolution of Steam Worlds: Energetic Aspects
Scientists Detect Precise Origin of Mysterious Signal From Deep Space
Victor Tangermann
Sun, August 24, 2025
FUTURISM
For almost two decades, astronomers have been trying in vain to explain extremely bright flashes of radio bursts emanating from deep space.
Despite only lighting up for a tiny fraction of a second, these fast radio bursts (FRBs) have been known to release as much energy as the Sun puts out in an entire year.
Now, in what's being called a "turning point," an international team of researchers has traced back the location of the origin of one of the brightest FRBs ever detected, allowing them to glean invaluable insights into the baffling phenomenon.
As detailed in a pair of new papers, astronomers used the Canadian CHIME/FRB radio-telescope to home in on an FRB, officially called 20250316A — but unofficially referred to as "RBFLOAT" for Radio Brightest Flash Of All Time" — which was first observed in March of this year near the Big Dipper.
Thanks to an array of "outrigger" telescopes spread out across North America, the team was able to pinpoint the origin of the FRB to a precise region that measures just 45 light-years across, significantly smaller than the average star cluster, in a galaxy some 130 million light-years away.
While that may sound somewhat overwhelming, given the fact that 45 light-years is roughly 30 times the diameter of our entire solar system, it's an impressive feat.
"The precision of this localization, tens of milliarcseconds, is like spotting a quarter from [62 miles] away," said lead author of one of the papers and McGill University-based postdoctoral researcher Amanda Cook in a statement. "That level of detail is what let us identify the host galaxy, NGC 4141, and match the burst with a faint infrared signal captured by the James Webb Space Telescope."
That kind of precision allowed teams to trace back the FRB's origin to a faint infrared signal, which was previously captured by NASA's James Webb Space Telescope.
"The high resolution of JWST allows us to resolve individual stars around an FRB for the first time," said Harvard research associate Peter Blanchard, lead author of the second paper, in the statement. "This opens the door to identifying the kinds of stellar environments that could give rise to such powerful bursts, especially when rare FRBs are captured with this level of detail."
"This was a unique opportunity to quickly turn JWST’s powerful infrared eye on the location of an FRB for the first time," he added in a separate Harvard press release, calling the faint infrared source an "exciting result."
"This could be the first object linked to an FRB that anyone has found in another galaxy," Blanchard said.
Despite the exciting advancement, we're still far from calling the mystery solved once and for all.
Researchers have previously suggested that magnetars, the extremely dense and highly magnetized remains of dead stars, or neutron stars, could be causing FRBs, sending powerful flashes of radio emissions at regular intervals like a lighthouse.
And that's just one of many candidates that have been put forward over the years.
Complicating matters is the fact that the astronomers have yet to observe 20250316A repeating itself. Other FRBs have been known to repeat and pulse in complex and highly regular patterns, adding to the overall mystery.
"It seems different energetically than the repeaters we’ve studied," explained McGill postdoc researcher and CHIME/FRB researcher Mawson Sammons. "We’re now re-examining some of the more explosive models that had fallen out of favor."
The team posits that the object spotted in the JWST observations could be a red giant, a Sun-like star nearing the end of its life cycle. An accompanying neutron star could be pulling mass away from the red giant, a process that may have triggered the outburst of radio emissions.
"Dozens of different ideas have been proposed to explain FRBs, but until now we haven’t had the data to test most of them," said coauthor and Harvard astronomy professor Edo Berger in the Harvard press release. "Being able to isolate individual stars around an FRB is a huge gain over previous searches, and it begins to tell us what sort of stellar systems could produce these powerful bursts."
"Whether or not the association with the star is real, we’ve learned a lot about the burst’s origin," Blanchard added. "If a double star system isn’t the answer, our work hints that an isolated magnetar caused the FRB."
The team is already gearing up in the hopes of being in the right place at the right time to catch the next FRB in the act.
"We can’t predict when and where the next FRB will come from, so we have to be ready to quickly deploy JWST when the time comes," Berger said.
More on FRBs: Scientists Propose Interesting Explanation for Mysterious Signals From Space
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