SPACE/COSMOS
New technique identifies stars that have swallowed planets
International research led by a team from the University of São Paulo suggests that stable systems, such as the Solar System, may be less common than previously thought. This has an impact on the emergence of complex life.
An international team led by researchers from the University of São Paulo (USP) in Brazil has developed an innovative method to identify stars that have consumed the planets around them. The technique detects variations in the abundance of beryllium, a relatively rare chemical element, and could open a new window into studying the evolution of planetary systems.
The study, published in the journal Astronomy & Astrophysics, analyzed a binary system consisting of two very similar stars, both of the solar type (with physical, chemical, and magnetic activity characteristics similar to those of our Sun), named HD 129171 and HD 129209. In principle, binary stars like these should have virtually the same chemical composition since they formed from the same molecular cloud (a cluster of dust and gas that acts as a stellar nursery). However, the researchers found significant differences between the two stars.
“The star HD 129171 is enriched in refractory elements – that is, elements that typically condense in the solid state and make up rocky planets. That strongly suggests that it has engulfed planetary material throughout its evolution,” says Anne Rathsam, a doctoral student at the Institute of Astronomy, Geophysics, and Atmospheric Sciences (IAG-USP) and the first author of the article. Rathsam is a FAPESP scholarship recipient.
Scientists had previously suspected that some stars might incorporate planets or planetary fragments. This new study is unique because it demonstrated for the first time that differences in beryllium abundance in binary stars can reliably indicate this process.
Beryllium has an important characteristic: it is not produced in the “heart” of stars throughout their evolution. Therefore, when astronomers detect the signature of this element in the light emitted by a star, it is a warning sign. This indicates that the star swallowed rocky material, such as planetary remnants, long after forming.
As the authors explain, lithium, beryllium, and boron are important exceptions in the chemical history of the universe. “All other chemical elements originate from primordial nucleosynthesis [the formation of the first atomic nuclei in the minutes following the Big Bang] or stellar nucleosynthesis [the nuclear fusion process that occurs inside stars throughout their lifetimes]. But not beryllium and boron. They primarily arise through a process called ‘cosmic spallation,’ in which high-energy particles fragment heavier nuclei, such as carbon, nitrogen, and oxygen, producing lighter elements,” explains Jorge Luis Melendez Moreno, an astronomer and professor at IAG-USP, as well as the study advisor.
Lithium is also produced primarily by spallation, although a minuscule amount of this element arose during primordial nucleosynthesis, and it can form in certain types of stars under special circumstances.
“Lithium had already been used as a possible indicator of planetary engulfment, but it’s destroyed relatively easily. Beryllium is more resistant, and its chemical signature can last longer,” Rathsam explains.
More than 11 Earth-like planets
The team conducted the study using data obtained with the UVES spectrograph installed on the European Southern Observatory’s (ESO) Very Large Telescope (VLT) in Chile. The instrument breaks starlight down into different wavelengths, enabling the identification of extremely subtle chemical signatures.
The observations revealed that HD 129171 has a notably higher concentration of refractory elements, including iron, magnesium, silicon, calcium, and titanium, compared to its companion, HD 129209. Additionally, the star exhibits an excess of both lithium and beryllium. According to the researchers, this pattern is consistent with the ingestion of rocky material equivalent to more than 11 times the mass of Earth.
“That material may have come from a single large planet or from several smaller bodies. However, in the case of Sun-like stars, internal mixing is so efficient that the final chemical signature doesn’t allow us to distinguish between those scenarios,” Rathsam comments.
The main original contribution of the study was the chemical analysis, which made it possible to identify beryllium as a marker of planetary engulfment events. The authors also discussed the dynamic mechanisms capable of causing planets to fall into their host stars, based on the existing literature. These mechanisms include gravitational interactions between planets, perturbations caused by companion stars, and orbital migration processes. They can make orbits highly eccentric and unstable, causing planets to be ejected from the system, collide with one another, or be absorbed by the central star.
An important implication of the study is that stable systems, such as the Solar System, may be rare. Melendez points out that several independent lines of evidence converge on this idea. Computational simulations of planetary formation indicate that configurations like that of the Solar System, with giant planets in nearly circular outer orbits and rocky planets in stable inner orbits, are not common. Furthermore, observational surveys of Sun-like stars have found few Jupiter-like planets in orbits comparable to that of Jupiter.
“When we bring together evidence from dynamical simulations, exoplanet observations, and chemical studies of binary stars, a consistent picture emerges, indicating that systems similar to the Solar System may be less common than we imagined,” the researcher explains.
Melendez also notes that binary systems are very common in the Milky Way. Current estimates indicate that approximately half of the galaxy’s stars have a gravitational companion. Since the two stars in a binary system form at virtually the same time and from the same molecular cloud, chemical differences between them are a strong indication that subsequent processes, such as the ingestion of planets, have altered their original composition.
“In our planetary system, the planets have relatively stable, low-eccentricity orbits. However, if planetary engulfment is common, it suggests that many systems undergo violent dynamic phases,” Rathsam emphasizes. According to her, this may have direct implications for the existence of complex life.
“Life wouldn’t just need billions of years to emerge and evolve. The planet would also have to remain in a sufficiently stable orbit to survive significant gravitational perturbations,” she explains.
In addition to shedding light on the evolution of planetary systems, the study has implications for theories of star formation and a technique called “chemical tagging.” This technique uses the chemical composition of stars to reconstruct the history of the Milky Way.
If the observed chemical differences in binary stars were caused by heterogeneities in the primordial cloud from which they originated, currently accepted models of star formation would require revision. However, the results obtained by the team support the planetary ingestion hypothesis.
The study included researchers from USP, the Polish Academy of Sciences, the Chinese Academy of Sciences, Monash University in Australia, and Italian astronomical observatories. The study received support from FAPESP through a Thematic Project coordinated by Melendez.
About São Paulo Research Foundation (FAPESP)
The São Paulo Research Foundation (FAPESP) is a public institution with the mission of supporting scientific research in all fields of knowledge by awarding scholarships, fellowships and grants to investigators linked with higher education and research institutions in the State of São Paulo, Brazil. FAPESP is aware that the very best research can only be done by working with the best researchers internationally. Therefore, it has established partnerships with funding agencies, higher education, private companies, and research organizations in other countries known for the quality of their research and has been encouraging scientists funded by its grants to further develop their international collaboration. You can learn more about FAPESP at www.fapesp.br/en and visit FAPESP news agency at www.agencia.fapesp.br/en to keep updated with the latest scientific breakthroughs FAPESP helps achieve through its many programs, awards and research centers. You may also subscribe to FAPESP news agency at http://agencia.fapesp.br/subscribe.
Article Title
Planet engulfment in the chemically anomalous HD 129171/HD 129209 pair
James Webb Space Telescope discovers that Chariklo’s invisible rings are changing
An international team led by the Institute of Astrophysics of Andalusia (IAA-CSIC) demonstrates for the first time that the two rings of this small Solar System body are changing in opposite directions
image:
Artistic view of the centaur Chariklo and its ring system. The bright point in the upper-right corner represents the Sun as seen from Chariklo’s distance.
view moreCredit: Credit: L. Maquet, Observatoire de Paris
Until just over a decade ago, ring systems were thought to be exclusive to the giant planets of the Solar System, such as Jupiter, Saturn, Uranus, and Neptune. However, in 2013, a small body barely 250 kilometers in diameter, located at nearly 17 times the Earth-Sun distance, joined this small group. The object is Chariklo, a small body orbiting between Saturn and Uranus, around which astronomers discovered two dense rings.
On October 18, 2022, the Institute of Astrophysics of Andalusia (IAA-CSIC) led an observation with the James Webb Space Telescope (JWST) to study Chariklo’s rings through a stellar occultation, a technique that measures the decrease in a star's light when an object passes in front of it. Now, a new study published in Science Advances and also led by the IAA-CSIC demonstrates, for the first time, that Chariklo’s ring system has undergone changes on timescales of just a few years.
“By comparing JWST observations with those obtained during other stellar occultations over the last decade, we discovered opposite changes in the two rings: while the inner ring shows significantly higher opacity, the outer ring shows lower opacity, ” explains Pablo Santos-Sanz, an IAA-CSIC researcher who leads the study.
This unexpected behavior indicates that Chariklo’s ring system is dynamic and may be subject to more complex physical processes than previously thought.
A SCIENTIFIC AND TECHNOLOGICAL MILESTONE
The study also represents a significant technological advance: the occultation by Chariklo was the first stellar occultation specifically predicted and planned for observation with JWST and successfully observed from the space telescope.
“Achieving this required knowing with extraordinary precision the orbit of Chariklo, the position of the star—thanks to ESA’s Gaia mission—and the trajectory of JWST itself around the L2 Lagrange point, a region of space located about 1.5 million kilometers beyond Earth, away from the Sun. JWST follows an orbit around this region that requires periodic corrections through station-keeping maneuvers,” notes Yücel Kilic, postdoctoral researcher at the IAA-CSIC and co-author of the study.
At the time of the occultation, Chariklo was moving relative to JWST at just 2.5 kilometers per second. This exceptionally low relative speed provided unprecedented spatial resolution for studying the structure of its rings. These rings are so narrow, and Chariklo is so far away, that they cannot be photographed directly, even with the James Webb Space Telescope or the largest ground-based telescopes. Stellar occultations allow astronomers to study them indirectly by measuring brief dips in a star's brightness as each ring passes in front of it.
Until now, scientists considered the rings around small bodies in the Solar System relatively stable. The changes detected in Chariklo challenge this view and suggest that these systems may be much more dynamic than previously thought. “Our results force us to rethink how they form, how they evolve, and what mechanisms maintain their stability. The ability to detect these changes opens a new window for understanding the evolution of these systems and, possibly, that of other ring systems in the Solar System,” says Santos-Sanz. The physical origin of the detected changes, however, remains an open question: they could reflect temporal evolution of the rings, differences related to the use of different filters, or a combination of both effects.
The Institute of Astrophysics of Andalusia (IAA-CSIC) led all phases of the study, from the project’s scientific design and the prediction of the occultation by Chariklo observed by JWST to the data analysis and the physical interpretation of the results. The IAA-CSIC team also played a fundamental role in ring modeling and the statistical analysis that demonstrated that the detected changes are real. The team carried out the work in collaboration with researchers from Spain, Brazil, France, Hungary, and the United States.
Schematic representation of the stellar occultation by Chariklo’s rings observed with the James Webb Space Telescope (JWST) on 18 October 2022. Comparison with previous occultations reveals opposite changes in the two rings: C1R shows a stronger signal, while C2R appears much weaker.
Journal
Science Advances
Method of Research
News article
Article Title
JWST stellar occultation reveals unexpected changes in Chariklo’s ring system’
Article Publication Date
9-Sep-2026
Soft and stretchy or rock solid? New modeling study sheds light on how the Earth got its moon
Simulations of the giant impact that is believed to have formed the moon need to take into account the geologic properties of the Earth and the moon's precursor
image:
New modeling studies that factor in geologic strength found fundamental changes in how the moon may have formed from the collision between a Mars-sized impactor and Earth. Simulations using older models that don’t factor in structural strength produce a debris disk (top), while the new models can produce an intact moon from the outset (bottom).
view moreCredit: NASA/JPL-CalTech/T. Pyle
For its size and location in the solar system, Earth has a surprisingly large moon. But how exactly the blue planet got its companion has vexed researchers for a long time. Researchers at the Southwest Research Institute and the University of Arizona used state-of-the-art computational techniques that revealed fundamental differences in how the moon may have formed from the collision between a Mars-sized object and Earth roughly 4.5 billion years ago.
Published in The Astrophysical Journal Letters, the results – for the first time – factor in the material strength of the two ancestral bodies and may change how researchers think the planetary collision happened. These impact simulations could change how researchers understand moon formation and may help constrain the timing of the event.
"We discovered that the preexisting geology of the Mars-sized proto-moon matters," said Adeene Denton, a former postdoctoral researcher at Lunar and Planetary Laboratory who is now at SwRI. "When you simulate the Earth and the moon as colliding bodies with geologic properties, it changes how the moon forms out of that impact – that's something we considered unnecessary before."
Earlier studies of the giant impact scenario include a foundational 2001 paper by Robin Canup, vice president of SwRI’s Solar System Science and Exploration Division in Boulder, Colorado, and Erik Asphaug, a professor at the Lunar and Planetary Laboratory and co-author of the current study. In the giant impact scenario, the debris from the collision of a Mars-sized body known as Theia with the early Earth obliterated Theia, scattering its remains into a disk around Earth. However, those simulations and subsequent giant impact modeling ignored material strength, which was thought to be insignificant for such high-energy events. Denton and her team revisited this hypothesis, using modern computational methods that incorporate temperature-dependent geologic strength for the first time.
"Because the collision was considered violent enough to melt and vaporize large portions of Earth and Theia, those previous papers assumed that it is okay to approximate them as fluids," Asphaug said. "Based on our new results, however, we think that it is time to reconsider that."
Denton revisited the hypothesis, for the first time using more advanced smoothed particle hydrodynamics simulations, or SPH, that take into account the structural strength of the bodies involved in the collision.
"It turns out material strength is really important when you're studying collisions between smaller bodies like asteroids, dwarf planets and moons," said Denton, who got the idea of applying the concept to Earth's moon while working on a previous paper about the formation of the Pluto-Charon system. "We weren’t sure if it would matter for our moon or not. When we did the simulations, we found it actually matters quite a bit."
This version of SPH, developed at the U of A and the University of Bern in Switzerland, uses a strength model that gives the bodies the kind of resistance to deformation that is expected for realistic geologic materials such as the rock and metals that would have made up Theia and the proto-Earth, or solid ice.
Hotter bodies are weaker than colder ones, and the team found that the different outcomes of Moon formation scenarios are sensitive to the temperatures of the colliding bodies. Some scenarios produce a fully intact moon within hours of the impact, while others result in a protolunar disk around the Earth that ultimately forms the moon over time. Because protoplanets generally start off hot and cool with age, this establishes an important new connection between the timing of the giant impact and the nature of the moon's initial state and assembly.
"Depending on how hot the Earth and moon are prior to the collision, the impact can destroy Theia and produce this massive disk of debris that eventually forms the moon," Denton said. "But when we used the same parameters as original impact modeling – down to the equal temperature structures inside both bodies – within around five hours, an intact moon emerged."
While intact moon outcomes have been seen in prior simulations, this work is the first to show that material strength and temperature play a central role in whether the moon forms intact or is assembled from material processed within a protolunar disk.
"These surprising and exciting new results imply a potential connection between the physical properties of the moon today, including perhaps its volatile content, and the thermal state of the Earth and Theia at the time of the giant impact," said Canup, who was not involved in the study. "This in turn might help scientists better constrain when the moon-forming event occurred."
The other conundrum remains the similarity of materials making up the Earth and the moon. As with prior models, explaining the close compositional makeup of the Earth and Moon remains an open scientific question.
"Because Earth and Mars formed in the same neighborhood of the solar system, they are like siblings," Denton said. "The moon and Earth are more like fraternal twins."
A possible explanation is that Theia and the proto-Earth formed from a common region of the solar system, while Mars, which is compositionally distinct from the Earth and Moon, formed farther away.
"We now know that the geophysical state of Earth and Theia play a fundamental role in shaping the outcome of the collision," said study co-author Namya Baijal, a doctoral student in Asphaug's group. "This gives us a new way to explore the conditions of the impact and what they might reveal about the moon's origin."
Watch the Moon formation simulations: https://www.youtube.com/watch?v=QAIRqc9dFHg
New modeling that accounts for material strength revealed fundamental changes in how the moon forms after a giant collision between a Mars-sized impactor and Earth. Simulations that neglect strength (top) produce a debris disk that forms the moon over time while those factoring in strength (bottom) can produce an intact moon right from the start.
Credit
Courtesy of SwRI
Journal
The Astrophysical Journal Letters
Method of Research
Computational simulation/modeling
Subject of Research
Not applicable
Article Title
Collisional Capture of an Intact Moon Depends on Strength
Article Publication Date
1-Sep-2026
Using helium, astronomers blow certainty into early Big Bang conditions
New data fortifies modern physics insights, researchers say
Ohio State University
COLUMBUS, Ohio – New observations regarding the composition of distant galaxies reveal insights into the earliest phases of the universe that confirm decades of scientific understanding of the elements and particles produced by the Big Bang, according to a new study.
Researchers used data from The Large Binocular Telescope (LBT) to measure the amount of helium — the second-most common element in the cosmos and a vital ingredient for the formation of life — in metal-poor nebulas, clouds of gas and dust in space where stars are sometimes born. Their findings strengthen long-held theories about how ancient elements, such as carbon and nitrogen, may have been dispersed in the period following the Big Bang.
Astronomers did this by analyzing helium signals in optical and infrared light to determine the temperature and density of the gases within faraway systems. After collecting 48 high-quality galactic samples, the team created a dataset aimed at significantly expanding researchers’ ability to infer the universe’s primordial helium abundance.
“Everything that we need to live here on Earth was once fused inside of a star,” said Miqaela Weller, lead author of the study and a PhD student in astronomy at The Ohio State University. “Understanding precisely where those elements come from helps inform us of how our universe evolved and how it will evolve in the future.”
The study was recently published as part of a series of papers in The Astrophysical Journal.
The work was completed as part of the LBT Yp project, a collaboration designed to accurately determine how much primordial helium was created at the universe’s beginning, an amount theorized to be largely dependent on the types of neutrinos, tiny and abundant subatomic particles, that were likely formed when the universe was only a second old.
If, for example, the amount of helium found in metal-poor galaxies is vastly different from astronomers’ current predictions, their results might challenge current theories about the universe’s early conditions as well as open the door to new, undiscovered physics, said Weller, who leads the infrared data reduction for the project
Still, it can be extremely difficult to peer into the universe’s past, as astronomers can only see up to about 400,000 years after the Big Bang, or when the universe became transparent enough to form the cosmic microwave background (CMB). Thus, by comparing their new observations with archival ones of the CMB, they can determine if current models of the universe are accurate.
“The importance of galactic archaeology cannot be understated,” said Weller. “The stars are within us, and learning more about them helps us determine our place within the universe.”
Roughly 90% of the universe’s helium formed during the Big Bang, with 10% originating from stars that have undergone nuclear fusion over the last 13.5 billion years. While researchers had previously only been able to estimate the universe’s helium abundance to a precision of about 2%, this work reduces that error to almost half a percent, a development that amounts to a huge leap in computational astrophysics, said Richard Pogge, a founding member of the project and a professor of astronomy at Ohio State.
“By making this exciting measurement, we’ve learned something fundamental about the universe,” said Pogge.
Scientists have theorized that all the raw materials of the universe emerged in the first few moments after its birth, including neutrinos. Until this paper’s result, it had been unclear whether the many subatomic particles that drive our modern grasp of particle physics appeared simultaneously or arrived later in an alternative, sequential way.
In searching for the answer, the team was challenged to locate extremely rare metal-poor galaxies, such as the tiny Leo P, as well as account for how Earth’s atmosphere could affect their data. Ultimately, their research confirmed that the number of neutrino species present at the Big Bang is, in fact, consistent with the standard model of particle physics, said Pogge.
“Finally having atomic data precise enough to show how the universe worked seconds after it began gives us the ability to make meaningful constraints on the nature of physics itself,” he said.
According to the team, the LBT Yp project plans to continue deciphering cosmic mysteries by constraining less-explored parameters of undiscovered metal-poor galaxies, likely with the aid of vast astronomical archives of collaboration projects like DESI.
“It’s going to take us many years to try to explore new galaxies and turn the techniques we’ve developed onto them,” Pogge said. “So it’s an enormous pleasure to be able to pass these decades-long findings onto those who are going to be the future of this field.”
Co-authors include Ohio State’s Jayde Spiegel as well as Evan Skillman and John H. Miller Jr. from the University of Minnesota, Erik Aver from Gonzaga University, Noah Rogers from Northwestern University, Danielle Berg from The University of Texas at Austin, and John Salzar from Indiana University. This work was supported by the National Science Foundation and Ohio State’s Center for Cosmology and AstroParticle Physics.
#
Contact: Richard Pogge, Pogge.1@osu.edu
Written by: Tatyana Woodall, Woodall.52@osu.edu
Journal
The Astrophysical Journal
Article Title
The LBT Yp Project. III. LUCI Spectra of Metal-poor Nebulae
Article Publication Date
9-Sep-2026
Researchers pinpoint key early-universe measurement with record precision
Data from the Large Binocular Telescope helped to reduce the uncertainty by a factor of three
image:
The research team focused on 15 of the most "pristine" small, remote galaxies ever discovered for these papers.
view moreCredit: NASA
MINNEAPOLIS / ST. PAUL (09/09/2026) — An international team, including researchers from the University of Minnesota Twin Cities, has reached a major milestone in "precision cosmology" by measuring the amount of helium created in the universe’s first five minutes with unprecedented accuracy.
The series of five papers published in The Astrophysical Journal details how the team was able to leverage 130 hours of observation time on the Large Binocular Telescope to reduce the uncertainty of this fundamental cosmic value to just 0.5% — three times better than previous standards.
The study’s findings provide new clues about the beginning of the universe and helps researchers better understand the fundamentals of physics. This experiment follows the tradition of testing the Standard Model in physics which, historically, has led to technological breakthroughs.
“This is a physics experiment on a grand scale and one of the biggest findings in my entire 40-year career,” said Evan Skillman, University of Minnesota College of Science and Engineering Distinguished Professor in the School of Physics and Astronomy. “It’s a fundamental number that tells us specifically about the conditions of our universe in its first five minutes. It has diagnostic power that speaks directly to the Standard Model of Physics.”
The Big Bang Theory shows how the universe expanded from an extremely high-density and high-temperature state approximately 13.8 billion years ago. The theory rests on three pillars: expansion of the universe, cosmic microwave background and the abundance of light elements like helium and deuterium. The last pillar — helium — hasn’t been studied and measured as extensively as the previous two pillars.
To reach this level of precision, the team moved away from traditional extrapolation methods — estimating an unknown value by extending a trend line of known data — which requires measuring many galaxies and estimating the initial helium level. Instead, they focused on 15 of the most "pristine" small, remote galaxies ever discovered. These galaxies are chemically unevolved that they act as “time capsules,” preserved almost exactly as they were shortly after the Big Bang.
Using advanced spectrographs built at Ohio State University, the researchers analyzed more than 10 helium lines and 15 hydrogen lines simultaneously. This allowed them to account for small systematic effects that were previously deemed negligible but become critical when aiming for sub-percent accuracy.
"The MODS spectrographs took 12 years to build from conception to first light on sky,” said Richard Pogge, College of Arts and Sciences Distinguished Professor of Astronomy at Ohio State University. “This is the kind of project we designed them to do, and to see them deliver is enormously satisfying. It’s not everyday you can help build instruments that measure something fundamental about our universe."
The precise measurement not only confirms history, but provides a precise look at the Standard Model of Physics. By determining the exact amount of helium, the team was able to calculate the number of neutrino families — the lightest subatomic particles — present in the early universe.
“We promised a half-percent uncertainty in our proposal, and we got there,” added Skillman. “In the unpredictable world of science, that doesn’t happen very often.”
In addition to the University of Minnesota Twin Cities and Ohio State University, the team included researchers from Gonzaga University, Northwestern University, The University of Texas at Austin, Indiana University, University of California Santa Cruz, University of Illinois, Universidad Nacional Autónoma de México and TRIUMF.
Learn more about the research on the IOP Publishing website.
Journal
The Astrophysical Journal
Article Title
The LBT Yp Project. I. An Improved Determination of the Primordial Helium Abundance—Project Description, Sample Selection, Observations, and Methodology
Article Publication Date
9-Sep-2026
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