Calculating black hole scattering for any mass ratio

Gravitational two-body scattering event with gravitational waves.

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State-of-the-art predictions can now be used to create waveform models for next-generation gravitational-wave detectors.

An international team, including researchers at the Max Planck Institute for Gravitational Physics (Albert Einstein Institute) in the Potsdam Science Park, has calculated with record precision how two black holes deflect each other's paths when they fly past one another under the influence of their mutual gravitational attraction. This novel result covers any mass ratio.

Gravitational-wave observatories routinely detect ripples in spacetime from colliding black holes. Decoding these signals requires predictions of black-hole motion, and these predictions must be accurate enough to keep pace with ever more sensitive detectors. Recently, methods borrowed from particle physics — treating gravity with the tools of quantum field theory developed for colliders — have driven rapid progress.

Using their worldline quantum field theory approach and high-performance computers, the researchers computed the energy-conserving part of the deflection angle at the fifth order of approximation in the strength of gravity. The key advance is completing the mass dependence at this order, where earlier results applied only to highly unequal pairs. The explicit analytic answer involves exotic mathematical functions related to higher-dimensional generalizations of torii, and a subtle infinity at one special fly-by speed cancels in their refined definition of energy-conserving effects. This state-of-the-art prediction may now be used for the waveform models required for next-generation gravitational wave detectors.

Paper abstract

Using the worldline quantum field theory formalism, we compute conservative contributions to the scattering angle and impulse for classical black hole scattering at fifth post-Minkowskian (5PM) and second self-force (2SF) order. This four-loop calculation involves non-planar Feynman integrals and requires advanced integration-by-parts reduction, novel differential-equation strategies, and efficient boundary-integral algorithms to solve a system of hundreds of master integrals in four integral families on high-performance computing systems. The resulting function space includes multiple polylogarithms as well as iterated integrals with a K3 period, which generate a spurious velocity divergence at v/c = √8/3, γ = 3. This divergence is present in the potential region and must be canceled by contributions from the radiative memory region, while its dimensional-regularisation pole should cancel against the radiative tail region. As the standard use of Feynman propagators fails to ensure this cancellation, we instead propose a “(γ-3)” conservative prescription that realises both cancellations, leading to a physically sensible answer. All available low-velocity checks of our result against the post-Newtonian literature are satisfied.

Source: Max Planck Institute for Extraterrestrial Physics/Research Highlights

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Dr. Elke Müller
Press Officer AEI Potsdam, Scientific Coordinator
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Email: elke.mueller@aei.mpg.de

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Publication Driesse, M.; Jakobsen, G. U.; Mogull, G.; Nega, C.; Plefka, J.; Sauer, B.; Usovitsch, J.
Conservative Black Hole Scattering at Fifth Post-Minkowskian and Second Self-Force Order. Physical Review Letters 137, 081402 (2026)

MPG.PuRe - DOI - pre-print

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One-sided spiral

NGC 4654

A spiral galaxy. It has a prominent spiral arm on one side (lower left) and a wide, glowing core. Dark brown filaments of dust swirl through its disc, while blue clusters of stars are found mostly going out to its arm. On the opposite side to the arm (upper right), gas trails off from the disc, out of the view in this image. A matching spiral arm is not visible on this side. The galaxy lies on a dark background. Credit: ESA/Hubble & NASA, D. Thilker, J. Lee and the PHANGS-HST Team

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The subject of this ESA/Hubble Picture of the Month is a spiral galaxy struggling against some of the titanic forces that appear on galactic scales in space. This is NGC 4654, an intermediate spiral galaxy in the constellation Virgo (the Maiden). “Intermediate” means that it lies between the spiral galaxies that have a bar across the centre and those that don’t, with a weak bar structure in its centre. It is situated 72 million light-years from Earth in the Virgo Cluster, a particularly massive and populous galaxy cluster.

NGC 4654 is particularly asymmetric, with a rounded and clearly-defined edge on one side and a long tail of gas stretching out from the opposite side — beyond Hubble’s view in this image. The cause of this gaseous tail is the same as for many of the other galaxies jostling in the crowded Virgo Cluster: namely, ram pressure stripping. NGC 4654 moves with such high velocity through space that it sweeps up and rams through the intracluster medium, the hot, rarefied gas filling the space between the Virgo Cluster’s galaxies. The intracluster medium in turn exerts a “ram pressure” on the galaxy, compressing the galaxy’s leading edge and tugging at its gas, creating the elongated tail.

It’s not just the galaxy’s gas that is unevenly distributed: its stars are too, and this is more unusual for a spiral galaxy. While the spiral arm on its leading edge is rich with stars and gas, the opposite arm noticeably lacks stars, influencing the galaxy’s lopsided spiral shape. It’s thought that ram pressure alone is unlikely to have had this effect. Rather, NGC 4654 has also been subjected to the gravitational force of the fellow Virgo Cluster galaxy NGC 4639. While the two galaxies are far apart now, it’s thought that a fly-by interaction between them around 500 million years ago ripped away NGC 4654’s gas along one side, limiting star formation there and creating the asymmetry in its shape.

Many galaxies that undergo ram pressure stripping suffer reduced star formation rates as the cold gas that collapses to form their stars is pulled away and lost. NGC 4654, however, is still forming nearly two Suns’ worth of stars every year, a rate comparable to other galaxies of similar size. The active star formation can be seen in the latest Hubble data used in this image, which picks up on a wavelength of red light that’s emitted by the clouds of energised gas where newborn stars lurk. The bright pink bubbles appear all across NGC 4654, from its forward spiral arm, to around its weak bar, and out to the edge of its disc.

The data used for this image come from two observing programmes (#15654, #17502) that have the aim of linking gas in galaxies with star formation. By observing many prominent galaxies in the vicinity of our own, researchers hope to better understand how gas moves around in galaxies, where and when it collapses to form stars and star clusters, and what effect those new stars have on the gas around them.

Source: ESA/HUBBLE/potm.

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Striking star clusters and irregular clumps

Arp 263(NGC 3239

An irregular galaxy, appearing like a broad band of tiny stars. It is denser on one side, with a faint cloud of gas among the stars. Clumps of brighter points are newly formed stars, with the largest lights being star clusters, and with many surrounded in glowing blue gas clouds. Plumes of red dust surround the galaxy. A foreground star appears very large and bright. A few distant alaxies appear in the background. Credit: ESA/Webb, NASA & CSA, A. Leroy

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The latest ESA/Webb Picture of the Month is a new, infrared look into the strange final phase of a galactic merger. Arp 263, an irregular galaxy, lies in the constellation Leo at a relatively nearby distance of around 25 million light-years.

Originally discovered in 1784 and also catalogued as NGC 3239, this galaxy was included in American astronomer Halton Arp’s Atlas of Peculiar Galaxies in 1966, as possibly one of the most remarkable and strange galaxies in the sample. Arp categorised it with the galaxies featuring “irregular clumps”. In 2023, the galaxy was featured in an image from the NASA/ESA Hubble Space Telescope, where these clumps are revealed to be bright nebulae between the galaxy’s dense clouds of gas, where stars are forming.

Arp 263 is believed to result from a past galactic merger. Apart from its unusual distorted shape, astronomers have noticed a few features that point to this. It has two short, curved tails of stars, beyond the field of view of this Webb image, which are a feature that’s associated with gravitational interactions. However, there are no nearby galaxies that Arp 263 could be interacting with now. The stars in the galaxy are oriented differently to its hydrogen gas, where they would normally be symmetric, and parts of that gas are moving at different velocities to each other. And, of course, the widespread formation of new stars across Arp 263 is typical of a galaxy whose gas has been seriously shaken up.

Although Arp 263 clearly hasn’t yet settled into a more regular shape after its gravitational tug-of-war, its former companion galaxy is now nowhere to be found. It’s possible that this was a dwarf galaxy small enough to have been already completely dissolved into the larger Arp 263 — or that its companion was simply much more heavy than it was bright, making it difficult to spot as a remnant.

This new image from Webb’s Near-Infrared Camera (NIRCam) reveals an entirely different view of Arp 263, taking us inside the thick gas crowding the galaxy to see the many stars scattered there. These old stars contrast with the several areas of star birth, where multitudes of new stars are forming in numerous clusters. Dust spread throughout the galaxy glows with the light, here shown in red, emitted by complex molecules; around the star-forming regions we also see — in blue colours — hydrogen gas, ionised by starlight and emitting its own light in turn. The most intense area of star formation features a curved chain of compact star clusters, leading to the largest and brightest star-forming nebula. Webb allows us to peek into this stellar nursery and see the stars that have formed within.

The brightest of the bright spots in Arp 263 is a shining star, named BD+17 2217. It appears so large and bright, with long diffraction spikes created by the telescope’s optics, because it is part of our own galaxy. The galaxies that appear in the background are much more distant, most hundreds of millions of light-years away from both us and Arp 263. A few of these galaxies are identifiable as spiral galaxies, but Webb’s NIRCam reveals the hundreds of much more distant galaxies lurking in the background as orange dots.Arp 263

This image was made with data from observing programme #3707 (PI: Leroy), a survey of the nearby, large, star-forming galaxies in the southern sky. These galaxies are close enough that Webb’s sharp vision can deliver a detailed picture of the stars, star clusters and interstellar dust within the galaxy. The observations will be used to better understand the cycle of star formation and how it plays out across galaxies; Arp 263, with its disturbed disc of gas and its chaotic star formation, presents a unique and fascinating target for these investigations.

Source: ESA/Webb/potm

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Subaru Telescope Archive Data Reveal Unexpected Surface Properties of a Comet

Figure 1: Comet 28P/Neujmin captured by the Subaru Telescope's Hyper Suprime-Cam (HSC) (white box and enlarged inset). The image shown is from one of HSC's 104 CCD detectors. In addition to the comet, the image contains more than 2,000 stars and galaxies. View the original images here (CCD image, Enlarged image). (Credit: NAOJ)

Comets are natural "time capsules," preserving ice and dust from the birth of the Solar System 4.6 billion years ago. Yet the solid nucleus of a comet is rarely observed directly, because it is normally hidden by a cloud of gas and dust known as a coma.

A research team including scientists from the University of Occupational and Environmental Health, Kyoto Sangyo University, and the National Astronomical Observatory of Japan discovered a nearly dormant, coma-free comet in publicly available archival data from the Subaru Telescope's Hyper Suprime-Cam (HSC). These observations enabled the first precise ground-based measurement of the reflectance properties of a cometary nucleus, providing new insights into how comets differ from asteroids and how they have evolved over time.

Why Are Cometary Nuclei Important?

Comets are small bodies composed primarily of ice and dust. They are thought to have formed in the outer Solar System and remained largely unchanged since the early days of the Solar System. Asteroids, by contrast, are rocky bodies found mainly between the orbits of Mars and Jupiter.

Comets and asteroids were once regarded as completely different types of objects. However, recent observations have blurred the distinction, with the discovery of water-bearing asteroids and cometary nuclei containing minerals similar to those found on asteroids.

Determining whether the surfaces of cometary nuclei are truly similar to those of asteroids—or fundamentally different—is an important step toward understanding how the bodies in our Solar System formed and how they have evolved over billions of years.

Why Are Cometary Nuclei Difficult to Observe?

Studying cometary nuclei directly is, however, extremely challenging. A cometary nucleus can be observed directly only when the comet is far enough from the Sun that its ice remains frozen and no coma forms. At such distances, comets are extremely faint—only very large-aperture telescopes can detect them.

In addition, investigating the surface properties of a cometary nucleus requires observations made under a special viewing geometry known as opposition, in which the observer views the comet with the Sun almost directly behind them (Figure 2).

Near opposition, the object appears brighter than usual, and the way its brightness changes provides clues to the properties of the particles covering its surface (Note 1). Opportunities to observe a comet under such favorable conditions are extremely rare.

Figure 2: Schematic illustration of opposition geometry.
Credit: NAOJ

A Chance Discovery in the Subaru Telescope Archive

The research team has been conducting a systematic search of publicly available archival data from the Hyper Suprime-Cam (HSC) Subaru Strategic Program (HSC-SSP) to identify Solar System objects serendipitously captured in the images.

During this search, they discovered Comet 28P/Neujmin at a distance of more than 10 astronomical units from the Sun—farther than from the Sun to Saturn—in a dormant state with no visible coma (Figure 1). Remarkably, the comet had been observed under nearly ideal conditions, close to opposition, where the Sun, the comet, and the Earth were almost perfectly aligned. This enabled the team to make the first clear ground-based detection of the opposition brightening of a cometary nucleus (Figure 3, left).

The discovery was made possible by the Subaru Telescope's 8.2-meter primary mirror, capable of detecting such a faint and distant cometary nucleus, together with HSC's exceptionally wide field of view, which allowed the comet to appear serendipitously in observations taken for a different scientific purpose.

A Comet That Looks Like an Asteroid—But Behaves Differently

The analysis showed that the surface color of Comet 28P/Neujmin closely resembles that of dark, reddish asteroids. These asteroids have very low reflectance and are thought to be rich in water-bearing materials. This result is consistent with previous studies.

However, when the researchers examined how the comet's brightness changed near opposition, they found an unexpected difference. These dark asteroids generally exhibit only a modest increase in brightness when viewed near opposition. In contrast, Comet 28P/Neujmin showed a much stronger brightening, comparable to that of high-reflectance asteroid types (Figure 3, right).

Figure 3: Brightening of Comet 28P/Neujmin near opposition (left) and comparison with different asteroid types (right). The left panel shows that the data point obtained at a Sun–comet–Earth phase angle of 0.33° (black circle), corresponding to an almost face-on viewing geometry, is significantly brighter than observations made at larger phase angles. Such a sharp increase in brightness is not seen in dark, low-reflectance asteroid types (D-, C-, and P-type; right panel). Instead, the brightening observed for Comet 28P/Neujmin is comparable to that of high-reflectance asteroid types (E-, S-, and M-type). (Credit: NAOJ)

These findings provide important clues about the fine-scale structure of the comet's surface, including the size of the surface grains, the amount of empty space between them, and the way the grains are packed together. The results suggest that although the nucleus of Comet 28P/Neujmin resembles low-reflectance asteroids in terms of its color and overall reflectance, its surface microstructure may be fundamentally different.

As comets repeatedly approach the Sun, their surface ice sublimates. This ongoing activity may have gradually produced a surface structure unlike that found on asteroids.

The Scientific Value of Archival Data

This study demonstrates how the combination of the Subaru Telescope's large aperture, HSC's wide field of view, and the publicly available HSC-SSP data archive can lead to unexpected discoveries, even for Solar System objects that were not the original targets of the observations.

Dr. Takafumi Ootsubo (University of Occupational and Environmental Health), lead author of the paper, comments, "The same archive likely contains many more Solar System objects waiting to be found. By applying the same observational approach to many more comets in the future, we hope to uncover how the surface structures of cometary nuclei have evolved over time, ultimately providing new insights into how Solar System bodies formed and evolved into the objects we see today."

This study was published in the Publications of the Astronomical Society of Japan (PASJ) on August 25, 2026 (Ootsubo et al., "Opposition effect of comet 28P/Neujmin observed with Subaru Hyper Suprime-Cam").

This research is based on data obtained with the Subaru Telescope and retrieved from the Hyper Suprime-Cam (HSC) data archive system operated by the Astronomy Data Center and the Subaru Telescope of the National Astronomical Observatory of Japan (NAOJ).

This work was supported by JSPS KAKENHI Grants (Nos. 23H01234, 23K25930, 24H00271, 23H01217, 23K25913, 23K22557, 24K00684, 25K24630, and 25K07393), in cooperation with the NEDO project "Technology Development of Next-Generation Computing for AI Chips Enabling High-Efficiency and High-Speed Processing," under the research program "Ultra-Large-Scale Data Analysis: Application to e-Science."

(Note 1) When an airless body is viewed almost directly from the direction of the Sun, shadows cast by surface particles become nearly invisible, making the surface appear brighter than usual. In addition, light scattered multiple times between the particles tends to be redirected back toward the observer, sometimes producing a sharp increase in brightness. This phenomenon is known as the opposition effect. By measuring the opposition effect, astronomers can infer physical properties of the surface, such as the size of the particles and how densely they are packed.

Source: Subaru Telesope

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About the Subaru Telescope

The Subaru Telescope is a large optical-infrared telescope operated by the National Astronomical Observatory of Japan, National Institutes of Natural Sciences with the support of the MEXT Project to Promote Large Scientific Frontiers. We are honored and grateful for the opportunity of observing the Universe from Maunakea, which has cultural, historical, and natural significance in Hawai`i.

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ALMA Reveals Long-Lived Hotspots on Betelgeuse’s Bubbling Surface

A Bubbling Betelgeuse - This ALMA image shows the submillimeter surface of Betelgeuse, revealing its irregular shape and regions of hotter gas. The brightest hotspot, toward the northeast of the star, appears at nearly the same location in ALMA observations separated by more than seven years, suggesting that some structures in Betelgeuse’s atmosphere can survive considerably longer than predicted by current models of stellar convection. Credit: ALMA (ESO/NAOJ/NRAO)/W. Dent et al.

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A remarkably detailed image obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) reveals the uneven surface of Betelgeuse, the famous red supergiant in the constellation Orion. The observations show bright hotspots and an irregular, corrugated outline shaped by the enormous motions taking place within the star.

Located roughly 600 light-years from Earth, Betelgeuse is one of the closest red supergiants and has a radius about 800 times that of the Sun. Its immense size makes it possible for ALMA to resolve structures across its atmosphere that would remain hidden in most other stars.

The new observations were obtained in 2023 using ALMA in its longest-baseline configuration, achieving a resolution as fine as about seven milliarcseconds. They reveal an atmosphere with an average temperature of around 2300 K and at least two hotter regions, to the northeast and southwest of the stellar disk. The brightest hotspot is up to about 800 K hotter than the surrounding gas.

These structures are thought to be linked to enormous convective motions inside Betelgeuse. Hot gas rising from deeper layers can generate shocks as it reaches the star’s outer atmosphere, producing the bright and uneven features detected by ALMA.

One finding particularly surprised the researchers. When they compared the 2023 observations with similar ALMA data obtained in 2015, the prominent northeastern hotspot appeared in almost the same location and with a similar intensity. This suggests that the feature has persisted for at least seven years — considerably longer than the lifetimes of large convective structures predicted by current models.

The surface itself is also far from spherical. ALMA measured variations of up to about six percent in its apparent radius, while fainter emission extends several stellar radii into Betelgeuse’s atmosphere. Observations of molecules including silicon monoxide (SiO) and carbon monoxide (CO) reveal an even more irregular and clumpy environment surrounding the star.

The orientation of the long-lived hotspots is also intriguing in light of recent evidence for a close companion to Betelgeuse, although the observations do not establish a direct connection. Continued high-resolution observations with ALMA could reveal whether the hotspots remain fixed and how they relate to convection, mass loss, and the structure of the star’s extended atmosphere.

Betelgeuse is approaching the final stages of its evolution and will eventually explode as a supernova. “Its eventual fate as a supernova makes it fascinating to know what it actually looks like now,” says lead author Bill Dent, an astronomer at ESO.

Source: ALMA (Atacama Large Millimeter/submillimeter Array)/Science Blog

Scientific Paper

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Additional Information

This post is based on the original published by the European Southern Observatory (ESO), an ALMA partner on behalf of Europe.

The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of the European Southern Observatory (ESO), the U.S. National Science Foundation (NSF), and the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Republic of Chile. ALMA is funded by ESO on behalf of its Member States, by NSF in cooperation with the National Research Council of Canada (NRC) and the National Science and Technology Council (NSTC) in Taiwan, and by NINS in cooperation with the Academia Sinica (AS) in Taiwan and the Korea Astronomy and Space Science Institute (KASI).

ALMA construction and operations are led by ESO on behalf of its Member States; by the National Radio Astronomy Observatory (NRAO), managed by Associated Universities, Inc. (AUI), on behalf of North America; and by the National Astronomical Observatory of Japan (NAOJ) on behalf of East Asia. The Joint ALMA Observatory (JAO) provides the unified leadership and management of ALMA's construction, commissioning, and operation.

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Stellar spin may explain why repeated black hole flares grow dimmer

A hydrodynamical simulation of a star being ripped apart by the tidal forces of a supermassive black hole.
Credit: NASA/ S. Gezari (JHU)/ J. Guillochon (UCSC)

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At the center of most galaxies lies a supermassive black hole, with a mass millions to billions of times that of our sun and some of the most extreme gravity in the universe.

Some stars that venture too close to such black holes live to tell the tale. Rather than being completely destroyed, they survive to make repeated close passes, producing a new flare of light each time.

These repeating partial tidal disruption events (rpTDEs) give astronomers the opportunity to watch the same star and black hole interaction unfold again and again, thanks to wide-field time-domain surveys that repeatedly scan large areas of the sky for objects that change in brightness.

But in several cases, researchers have noticed a puzzling pattern: The successive flares grow progressively dimmer. For years, theoretical models couldn't explain why.

Now, a team of astrophysicists at Syracuse University has shown that the answer may lie in a previously overlooked factor—the star's spin.

The study, published in The Astrophysical Journal, was led by doctoral student Ananya Bandopadhyay, working with postdoctoral researcher Benjamin Amend and associate professor Eric Coughlin—all in the Department of Physics—as well as colleagues at other institutions.

When stars meet black holes

In a typical tidal disruption event (TDE), a black hole's tidal force—the difference in gravitational pull across a nearby star—tears the star completely apart.

As the disrupted stellar debris falls toward, or "accretes" onto, the black hole, it loses energy that is emitted in the form of light over the course of days to months.

While black holes themselves emit no light, TDEs provide a short-lived supply of fuel that lights up the surrounding region, allowing astronomers to study these otherwise invisible objects indirectly.

If a star orbiting a black hole does not come close enough to be completely ripped apart, it can, however, lose a fraction of its mass, resulting in a partial TDE. In a repeating partial TDE, the surviving core continues orbiting the black hole, losing more material with each new close pass, a few months to several years apart.

The dimming mystery

How much material a star loses during repeated encounters depends partly on its internal structure. Bandopadhyay compares a low-mass star to a fluffy meringue, which can become increasingly vulnerable to the black hole's tidal forces.

By contrast, a higher-mass star has a more centrally concentrated, onion-like structure and can shed its outer layers while its dense core remains relatively unaffected, losing decreasing amounts of mass over time.

Those differences can help explain why rpTDEs don't all behave the same way. But one pattern in particular has mystified researchers. Of the roughly 10 repeating systems identified to date, four have produced flares that grow progressively dimmer.

Decreasing mass loss might seem like an obvious explanation. But previous hydrodynamical simulations showed that, surprisingly, even as the material lost decreased with each encounter, the predicted flares retained roughly the same brightness.

"We were puzzled by this for two years," Bandopadhyay says.

Their previous work had revealed another effect of the black hole's tidal forces. In addition to stripping material from the star, they exert a torque that causes the star to spin faster with each close encounter. As a result, although less material falls back toward the black hole, it returns over a shorter period of time, helping to keep the predicted flare at roughly the same brightness.

To reproduce the dimming astronomers were actually observing, the researchers needed what Bandopadhyay called "a new ingredient"—a star that was already spinning rapidly before its first encounter with the black hole.

The new study found that this initial rotation prevents the star from being significantly spun up during each passage. Without that additional spin-up, the timescale over which the stripped material falls back remains relatively constant. As the star loses less material with each encounter, the peak fallback rate—and the predicted brightness of the flare—can finally decline.

Tracing the star's past

But why would the star already be spinning so rapidly?

"It is also extremely difficult to 'bind' a star to a supermassive black hole so tightly that it orbits the black hole in a matter of months, and yet they seem to do so in rpTDEs," Coughlin says.

The so-called Hills mechanism may explain both. Under this scenario, a pair of closely orbiting stars passes near a supermassive black hole, which tears the binary apart, ejecting one star and capturing the other.

In a close binary, the stars can become tidally locked, causing each to rotate on its axis at the same rate that the pair orbits each other. The tighter the binary, the shorter that orbital period and the faster a tidally locked star spins. The binaries capable of leaving a captured star on the short orbit observed in rpTDEs would have to be extremely tight—also leaving a tidally locked star spinning rapidly before its capture.

"Ananya's work demonstrates that each of these peculiarities can be explained by the same underlying phenomenon: the tidal destruction of a binary system and the capture of one of the stars," Coughlin says. "From a theoretical standpoint, this is a major step forward in our understanding of the physics at play in these systems."

Zooming out, Coughlin notes that Hills capture may also have produced some of the stars orbiting Sagittarius A*, the supermassive black hole at the center of the Milky Way. The new findings could therefore help explain some of the properties of stars in what he calls "our own cosmological backyard."

by Olivia Hall, Syracuse University

edited by Sadie Harley, reviewed by Robert Egan

Source: Phys.org

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Publication details

Ananya Bandopadhyay et al, The Role of Stellar Spin in Repeating Partial Tidal Disruption Events, The Astrophysical Journal (2026). DOI: 10.3847/1538-4357/ae8f31

Journal information: Astrophysical Journal

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Provided by Syracuse University

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Strange Signals Called Long-period Radio Transits Come From Cataclysmic Variables

This iullustration shows a white dwarf star accreting material from its companion. New research says that this can explain at least one of the puzzling Long Period Radio Transients, mysterious radio signals that repeat with periods ranging from a few minutes to a few hours. Image Credit: Carl Knox (OzGrav, Swinburne University of Technology) and Joshua Preston Pritchard (CSIRO).

Long period radio transients (LPTs) are mysterious signals coming from objects inside our galaxy. They're highly polarized, coherent radio bursts that repeat regularly, with periods ranging from a few minutes to a few hours. Scientists detected hints of the first LPT in 2005, and now they know of many more of them.

So far, an explanation has lagged behind their detections, but new research has an explanation for at least one of them. The research is titled "Periodic radio and X-ray emission from an accreting white dwarf binary," and it's published in Nature Astronomy. The lead author is Kovi Rose, a PhD student from the University of Sydney’s School of Physics and CSIRO.

"Little is known about the physical origins of these systems," the authors write. "Astronomers have proposed magnetars that rotate slowly and white dwarfs that rapidly orbit with a companion star as potential explanations."

Recent examples of LPTs support the idea that white dwarfs with a companion are responsible for LPTs. But the actual mechanism that creates them has remained unclear.

In this work, the researchers present the discovery, and explanation, of a new LPT named LPT ASKAP J174508.9-505149. The new LPT, referred to as J17 in this article, has a 1.3 hour orbit, and "exhibits orbitally modulated X-ray emission and radio bursts," the authors write. "These elliptically polarized radio bursts drift in emission frequency, potentially due to a longer beat period, and turn off for several hours at a time."

J17's radio signal switches off for hours at a time, a wrinkle that's a clue to the mechanism behind the LPT. The pulse frequencies also drift up and down over a longer beat period. "ASKAP J1745-5051 exhibits pulse properties not previously observed in LPTs, providing valuable insights into the progenitor system," the authors write. J17's signal is dynamic in other ways, too.

The researchers say that the LPT is coming from a magnetic cataclysmic variable (CV), a binary star where one is a highly magnetized white dwarf, and the other is a donor star.

“For the first time we have pinpointed the origin of these signals, confirming the source to be a ‘cataclysmic variable’, or an accreting white dwarf star,” lead author Rose said in a press release. “Long-period radio transients have puzzled astronomers for years,” Rose added. “We’ve only found about a dozen, and their origins have been unclear. Now, we’ve been able to show that the source for one of these transients comes from a white dwarf actively pulling material from a companion star.”

Binary stars where one is a white dwarf drawing material from a donor star are responsible for Type 1a supernova explosions. In those cases, the white dwarf accumulates so much material from its partner that it eventually explodes, obliterating the star.

But in cataclysmic variables, things play out differently. And while LPTs might seem similar to pulsars, they're distinctly different.

"The pulsing that we see is not coming from a spin. We think it’s coming from an orbit,” said study co-author David Kaplan, Professor of Physics and Astrophysics at the University of Wisconsin Milwaukee . “In order for (these binary stars) to orbit once every 80 minutes, they have to be both very small and very close together. In fact, they’re probably so small and so close together that some material from one star is spilling out onto the other star, and that gives rise to a particular signature that we saw in some observations that really ties it to this class of cataclysmic variables (which have been widely studied for the past hundred years).”

The CV in this work includes a white dwarf about the size of Earth, but with a mass about the same as the Sun. The companion star is a red dwarf with about 1/10th of the Sun's mass. The pair orbit very close to one another, completing an orbit in a little more than an hour.

There's an x-ray component to J17, and that comes from donor star material that gathers on the white dwarf's surface and heats up, emitting x-rays. But the radio bursts don't emanate from that. Instead, they're generated by the stars' interacting magnetic fields.

“These emissions are all tied to the orbital motion of the system,” Rose said. “But interestingly, the radio and X-ray signals don’t peak at the same time, which tells us they’re being produced in different regions of the system.”

This figure from the research shows some of the signals received from ASKAP J1745−5051. There's a lot her for non-scientists to decipher, but the main takeaway is that it correlates emissions with phases in the cataclysmic variable. ATCA, MKT, and ASKAP are all radio telescope arrays. The y-axis shows radial velocity, and it's always zero during phase 2 and phase 4, a clue to the nature of the emissions. Image Credit: Rose et al. 2026. NatAstr.

J17's intermittent signals and pulses arise from the system's plasma and magnetic fields. "Varying conditions in the local plasma density and magnetic field interaction may explain the intermittency and unique pulse morphologies in the observed radio pulsations from ASKAP J1745-5051," the authors write. "Our observations of ASKAP J1745-5051 demonstrate that magnetically driven accretion plays a key role in the generation of emission across the electromagnetic spectrum in magnetic CVs, including coherent radio pulses and variable X-ray emission."

Artists’ impression of a white dwarf binary system ASKAP J1745-5051

There have been hints that binary stars are behind LPTs, but this study presents the best evidence yet. The authors say that J17's modulated radio and x-ray emissions are associated with its orbital period, and that it "clearly establishes that accreting CVs make up at least part of the population of LPTs."

“Some similar objects had been linked to binary systems before, but this is the first one where we can clearly see both stars and the accretion process in action,” said co-author Tara Murphy, Professor in the University of Sydney's School of Physics. J17 can be an important reference point in the study of LPTs, according to the researchers. “This system gives us a way to decode these signals. It could help us determine whether other long-period transients are more like pulsars or like white dwarf systems, acting like a stellar Rosetta stone,” lead author Rose said.

J17 is also important in another way, one that it shares with other high-energy astrophysical objects. “These systems are natural laboratories,” Mr Rose said. “They allow us to test our understanding of how matter behaves in strong magnetic fields and under intense gravitational forces.”

The question now is, can these cataclysmic variables explain the entire class of LPTs, or are their multiple sources?

"Determining if these processes can explain the properties of the entire emerging class of LPTs will require detailed simulations and modelling, as well as the discovery and investigation of new LPTs," the authors conclude.

By Evan Gough

Source: Universe Today

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Evan Gough is a science-loving guy with no formal education who loves Earth, forests, hiking, and heavy music. He's guided by Carl Sagan's quote: "Understanding is a kind of ecstasy."

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Probing Dust in the Disk of a Growing Giant Planet

This image from the Atacama Large Millimeter/submillimeter Array (ALMA) shows the protoplanetary disk around the young star PDS 70. To the right of the central star is a faint source thought to be a growing planet surrounded by a circumplanetary disk. Adapted from ALMA (ESO/NAOJ/NRAO)/Benisty et al.; CC BY 4.0

A closeup of PDS 70c’s circumplanetary disk within PDS 70’s protoplanetary disk.

Credit: ALMA (ESO/NAOJ/NRAO)/Benisty et al.; CC BY 4.0

New research suggests that the circumplanetary disk surrounding the exoplanet PDS 70c contains a ring of dense dust, and the conditions within this ring may allow baby moons to form.

A Disk Within a Disk

The young star PDS 70 has become famous for its protoplanetary disk and its two growing giant planets, PDS 70b and PDS 70c. At least one of these planets is surrounded by a disk of its own; in 2019, researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) reported the first-ever observation of a circumplanetary disk around PDS 70c, and later observations with ALMA brought clearer views of this disk.

There’s still debate over the exact source of the emission detected by ALMA. Does this emission come from dust, and if so, how is the dust distributed? Is the disk optically thick or optically thin? Does the emission even come from dust, or could it instead be free–free emission from unbound electrons navigating a charged-particle maze? 

Dust and gas surface density for the modeled disks in the drift (orange) and ring (blue) models. 

Adapted from Shibaike et al. 2026

Dust Diagnosis

Yuhito Shibaike (Kagoshima University) and collaborators recently examined the hypothesis that the emission from PDS 70c’s circumplanetary disk arises from dust distributed in an optically thick ring. To test this hypothesis, the team explored two possible dust distributions, which they call “drift” and “ring.” In the drift model, dust grains within the circumplanetary disk migrate inward toward the planet, leaving much of the disk optically thin. Modeling suggests that this migration is typical in protoplanetary disks, and it might be common in circumplanetary disks as well.

In the ring model, the dust grains are concentrated within an optically thick ring at a certain distance from the planet. Simulations suggest that the formation of this type of dust ring is feasible, arising from a localized increase in gas density, outflows, or other causes.

Shibaike and coauthors found that the ring model naturally reproduced the observed spectral energy distribution for a range of reasonable parameters. The drift model, on the other hand, required an unrealistically high dust-to-gas ratio for the material accreted onto the circumplanetary disk from the parent protoplanetary disk to reproduce the observed spectral index.

Finally, if the dust surrounding PDS 70c is concentrated within a ring, what does that mean for the possibility of moons forming within the disk? Shibaike and collaborators found that the conditions within the ring likely satisfy the requirements of both the streaming instability and the gravitational instability, which are required for dust grains to clump together and form the rocky building blocks of baby moons. Perhaps the PDS 70 system will one day be the site of not only a circumplanetary disk, but an exomoon as well!

Comparison of ALMA observations (colored symbols) and model predictions (colored lines) from the drift (orange) and ring (blue) models. Adapted from Shibaike et al. 2026

Future Prospects and Moon-Making Possibilities

This work demonstrated the feasibility of the dust-ring model, but it didn’t rule out a contribution due to free–free emission from unbound electrons, which has also been proposed to explain the disk’s appearance. The team noted that distinguishing between thermal dust emission and free–free emission is challenging with existing data, as the two sources produce spectral energy distributions with similar shapes.

Luckily, this likely won’t remain a mystery forever: the next-generation Very Large Array, which is anticipated to begin full science operations in the mid-2030s, should be able to resolve the location of the dust within the circumplanetary disk and illuminate the source of emission.

Finally, if the dust surrounding PDS 70c is concentrated within a ring, what does that mean for the possibility of moons forming within the disk? Shibaike and collaborators found that the conditions within the ring likely satisfy the requirements of both the streaming instability and the gravitational instability, which are required for dust grains to clump together and form the rocky building blocks of baby moons. Perhaps the PDS 70 system will one day be the site of not only a circumplanetary disk, but an exomoon as well!

Citation

“Interpreting ALMA Multiwavelength Continuum Observations of PDS 70 c: An Optically Thick Dust Ring in the Circumplanetary Disk,” Yuhito Shibaike et al 2026 ApJL 1006 L26. doi:10.3847/2041-8213/ae86f5

Source: American Astronomical Society/AAS-Nova

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Milky Way's fastest star orbits our supermassive black hole so closely it feels its spin

PR Image eso2612a
VLT images of the S301 star orbiting Sagittarius A*

PR Image eso2612b
VLT images of the S301 star orbiting Sagittarius A* (square layout)

PR Image eso2612c
VLT images of S301 and other S-stars orbiting Sagittarius A*

PR Image eso2612d
Illustration of the Lense-Thirring effect

PR Image eso2612e
Effect of a spinning black hole on the orbit of the S301 star

PR Image eso2612f
Wide-field view of the centre of the Milky Way

PR Image eso2612g
Sagittarius A* in the constellation of Sagittarius

PR Image eso2612h
New look at the stars around the Milky Way's centre

PR Image eso2612i
Four lasers for the VLTI

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Videos


PR Video eso2612a
Does the Milky Way central black hole rotate? This star could tell us | ESO Chasing Starlight


PR Video eso2612b
Time-lapse of the S301 star orbiting Sagittarius A*


PR Video eso2612c
Effect of a spinning black hole on the orbit of the S301 star


PR Video eso2612d
Animation of the Lense-Thirring effect


PR Video eso2612e
Disruption of a binary star close to a black hole

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Astronomers have discovered the fastest known star in our galaxy, the Milky Way, orbiting the black hole at its centre. The star, named S301, was detected with the European Southern Observatory’s Very Large Telescope Interferometer (ESO’s VLTI) and reaches speeds of 25 000 km/s as it travels around the four-million-Solar-mass black hole. It comes closer to it than any other observed before, so close that it feels the effects of the black hole’s rotation.

“Decades carefully tracking stars orbiting our galaxy’s central black hole, Sagittarius A*, have led to this breakthrough discovery of a very promising star. Because it orbits so close to Sagittarius A*, S301 opens a new window to the fundamental properties of spacetime in this extreme black-hole environment,” says Nobel Prize winner Reinhard Genzel, Director at the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching, Germany, and founding member of the collaboration that made the new observations.

“What is special about this star is that it’s orbiting Sagittarius A* on a very tight orbit, taking just 8.7 years to complete it, and is approaching the black hole at a mere 12 times the distance of Earth to the Sun. That is unprecedented,” says Felix Mang, PhD student at MPE and author of the study published today in Nature

During its closest passage to the black hole, the star travels at around 25 000 kilometres per second — 100 000 times faster than a commercial plane, or over 8% of the speed of light — making it the record holder for the fastest star in the Milky Way. S301 also comes closer to Sagittarius A* than any other star observed so far, approaching the black hole at around the distance of Saturn to the Sun. [1] Because S301 comes so close to Sagittarius A*, it is the first star known that could be used to directly measure the rotation of a black hole.

Like most things in our Universe, astronomers predict that Sagittarius A* spins. According to Einstein’s general theory of relativity, a spinning black hole drags spacetime along with it and twists it, which impacts the orbits of surrounding stars. The effect is felt more strongly for objects orbiting fast-rotating black holes at close range.

“With this star we hope to measure, within the next 10 years, the spin of the black hole," says Mang. MPE researcher Stefan Gillessen, who also had a leading role in the new study, adds: “For the first time, we would actually be able to measure very directly the spin of a massive black hole, which would be a key test of Einstein’s theory.” Juan Osorno, an astronomer at LIRA Observatoire de Paris–PSL, France, who also had a key role in the study adds: “Without this star, we would need to measure the motion of other stars for several more decades to get anywhere close to measuring the spin of the black hole.”

Finding S301, which appears two billion times fainter than Betelgeuse (the orange star in the constellation Orion) in the sky, was no easy feat. The team used the VLTI, a facility at ESO’s Paranal Observatory in Chile and its GRAVITY instrument, now known as GRAVITY+ following an infrastructure upgrade. [2] The VLTI’s superpower lies in its ability to combine the light from four 8-metre telescopes to create a ‘virtual’ telescope with 15 times the spatial resolution of a single 8-metre telescope.

“Worldwide, Paranal is the only place where you can do this type of observations because no other observatory in the world has four 8-metre telescopes that can act together as an interferometer,” says co-author Frank Eisenhauer, GRAVITY+ Principal Investigator and Director at MPE.

With GRAVITY, and later with GRAVITY+, the team managed to catch a first glimpse of the new star in spring 2023 and have followed it since to constrain its orbit. They could also trace S301’s orbital history back to 2017, finding that it last made its closest approach to the central black hole in early 2023. S301’s orbital properties, and the fact that stars cannot form so close to a massive black hole, indicate that the star was likely part of a binary pair that was torn apart by the tidal forces of Sagittarius A*. In the process, S301 became trapped by the black hole’s gravity while its companion star was kicked out with high velocity, most likely enough to leave the galaxy altogether.

Follow-up observations with GRAVITY+, and with the MICADO instrument on ESO’s upcoming Extremely Large Telescope (ELT), will be crucial for tracing S301’s path over the next decade, as it makes its next closest passage in 2031. Observing at least two complete orbits of S301 allows its trajectory to be constrained with high enough precision to enable the team to directly determine the spin of Sagittarius A* for the first time. “That would be a dream come true,” says Mang.

Source: ESO/News

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Notes

[1] At its closest approach, the star passes just 1.78 billion km from the black hole, around 12 times the Sun-Earth distance or just 20% larger than the Sun-Saturn distance.

[2] Following decades mapping stars orbiting the Milky Way’s centre using different ESO facilities, the team has been using the GRAVITY instrument on the VLTI for this purpose interferometer, called GRAVITY+, has been implemented gradually over the last few years, and has allowed them to find increasingly fainter objects.

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More information

This research was presented in a GRAVITY+ Collaboration paper titled “Discovery of a star sensitive to the spin of Sgr A*” to appear in Nature (doi: 10.1038/s41586-026-10894-w).

The team is composed of: K. Abd El Dayem (LIRA, Observatoire de Paris, Universitê PSL, CNRS, Sorbonne Université, Université de Paris, France), R. Abuter (European Southern Observatory, Garching, Germany [ESO Germany]), N. Aimar (Faculdade de Engenharia, Universidade do Porto, Portugal [FEUP], and Centro de Astrofísica e Gravitação, IST, Universidade de Lisboa, Portugal [CENTRA]), P. Amaro-Seoane (Universitat Politècnica de València, Spain and Max Planck Institute for Extraterrestrial Physics, Garching, Germany [MPE]), A. Berdeu (ESO and LIRA), J. P. Berger (Univ. Grenoble Alpes, CNRS, Grenoble, France [IPAG]), G. Bourdarot (MPE), W. Brandner (Max Planck Institute for Astronomy, Heidelberg, Germany [MPIA]), A. Burkert (University Observatory, Faculty of Physics, Ludwig-Maximilians-Universität, Munich, Germany [LMU] and MPE), D. Calderon (Max Planck Institute for Astrophysics [MPA], Garching, Germany), C. Correia (FEUP and CENTRA), J. Cuadra (Universidad Adolfo Ibañez, Viña del Mar, Chile and Millennium Nucleus on Transversal Research and Technology to Explore Supermassive Black Holes [TITANS], Chile), R. Davies (MPE), D. Defrère (Institute of Astronomy, KU Leuven, Belgium [KU Leuven]), L. Delit (LIRA), A. Drescher (IPAG and MPE), F. Eisenhauer (MPE and Department of Physics, Technical University of Munich, Germany [TUM]), L. Esteras Otal (ESO Germany), M. Fabricius (MPE), H. Feuchtgruber (MPE), N. M. Förster Schreiber (MPE), A. Foschi (LIRA), P. Garcia (FEUP and CENTRA), R. Garcia Lopez (School of Physics, University College Dublin, Ireland), A. Generozov Astronomy Dept. and Oden Institute, University of Texas at Austin, USA), R. Genzel (MPE and Departments of Physics Astronomy, Le Conte Hall, University of California, Berkeley, USA) S. Gillessen (MPE), F. Gonté (ESO Germany), X. Haubois (European Southern Observatory, Santiago, Chile [ESO Chile]), S. F. Hönig (School of Physics & Astronomy, University of Southampton, United Kingdom [Southampton]), M. Houllé (IPAG), S. Joharle (MPE), A. Kaufer (ESO Chile), J. Kammerer (ESO Germany), P. Kervella (LIRA), J. Kolb (ESO Germany), L. Kreidberg (MPIA), R. Laugier (KU Leuven), S. Lacour (LIRA), O. Lai (Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange [Lagrange]), J.-B. Le Bouquin (IPAG), J. Leftley (Southampton) B. Lopez (Lagrange), D. Lutz (MPE), F. Mang (MPE and TUM), A. Mérand (ESO Germany), F. Millour (Lagrange), M. Montargès (LIRA), N. Morujão (FEUP and CENTRA), H. Nowacki (Lagrange), M. Nowak (LIRA), S. Oberti (ESO Germany), J. Osorno (LIRA), T. Ott (MPE), T. Paumard (LIRA), C. Paladini (ESO Chile), H. B. Perets (Physics department, Technion - Israel Institute of Technology, Haifa, Israel), K. Perraut (IPAG), G. Perrin (LIRA), R. Petrov (Lagrange) P. O. Petrucci (IPAG), T. Piran (Racah Institute of Physics, The Hebrew University of Jerusalem, Israel [Racah]), N. Pourré (IPAG), S. Rabien (MPE), D. C. Ribeiro (MPE), S.Robbe-Dubois (Lagrange), M. Sadun Bordoni (MPE), J. Sánchez Bermúdez (Instituto de Astronomía, National Autonomous University of Mexico, Mexico), D. Santos (MPE), R. Sari (Racah) J. Sauter (MPIA), S. Scheithauer (MPIA), J. Scigliuto (Lagrange) J. Shangguan (MPE), T. T. Shimizu (MPE), F. Soulez (Univ. Lyon, Univ. Lyon 1, ENS de Lyon, CNRS, Centre de Recherche Astrophysique de Lyon, France), J. Stadler (LMU), C. Straubmeier (1st Institute of Physics, University of Cologne, Germany), E. Sturm (MPE), M. Subroweit (Cologne), C. Sykes (Southampton), L. J. Tacconi (MPE), P. Thévenet (LIRA), I. Urso (LIRA), F. Vincent (LIRA), J. Woillez (ESO Germany), G. Zins (ESO Chile).

The European Southern Observatory (ESO) enables scientists worldwide to discover the secrets of the Universe for the benefit of all. We design, build and operate world-class observatories on the ground — which astronomers use to tackle exciting questions and spread the fascination of astronomy — and promote international collaboration for astronomy. Established as an intergovernmental organisation in 1962, today ESO is supported by 16 Member States (Austria, Belgium, Czechia, Denmark, France, Finland, Germany, Ireland, Italy, the Netherlands, Poland, Portugal, Spain, Sweden, Switzerland and the United Kingdom), along with the host state of Chile and with Australia as a Strategic Partner. ESO’s headquarters and its visitor centre and planetarium, the ESO Supernova, are located close to Munich in Germany, while the Chilean Atacama Desert, a marvellous place with unique conditions to observe the sky, hosts our telescopes. ESO operates three observing sites: La Silla, Paranal and Chajnantor. At Paranal, ESO operates the Very Large Telescope and its Very Large Telescope Interferometer, as well as survey telescopes such as VISTA. Also at Paranal, ESO will host and operate the south array of the Cherenkov Telescope Array Observatory, the world’s largest and most sensitive gamma-ray observatory. Together with international partners, ESO operates ALMA on Chajnantor, a facility that observes the skies in the millimetre and submillimetre range. At Cerro Armazones, near Paranal, we are building “the world’s biggest eye on the sky” — ESO’s Extremely Large Telescope. From our offices in Santiago, Chile we support our operations in the country and engage with Chilean partners and society.

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Links

• Research paper
• MPE press release, including a press kit with additional broadcaster material
• Photos of the VLT/I
• Find out more about ESO's Extremely Large Telescope on our dedicated website and press kit
• For journalists: subscribe to receive our releases under embargo in your language
• For scientists: got a story? Pitch your research

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Contacts:

Felix Mang
Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000-3713
Email: fmang@mpe.mpg.de

Stefan Gillessen
Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000 3839
Cell: +49 176 99 66 41 39
Email: ste@mpe.mpg.de

Juan Osorno
Laboratory for Instrumentation and Research in Astrophysics (LIRA), Observatoire de Paris, PSL University
Meudon, France
Email: Juan.Osorno@observatoiredeparis.psl.eu


Director, Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000-3100
Email: eisenhau@mpe.mpg.de

Reinhard Genzel
Director, Max Planck Institute for Extraterrestrial Physics
Garching bei München, Germany
Tel: +49 89 30000 3281
Email: genzel@mpe.mpg.de

Xavier Haubois (for questions on VLTI)
European Southern Observatory
Paranal Observatory, Atacama Desert, Chile
Email: Xavier.Haubois@eso.org

Bárbara Ferreira
ESO Media Manager
Garching bei München, Germany
Tel: +49 89 3200 6670 (unavailable before 17 August)
Cell: +49 151 241 664 00 (unavailable before 17 August)
Email: press@eso.org

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Even Near a Supermassive Black Hole, Stars Enrich the Interstellar Medium

The JWST used NIRCam and MIRI to capture this region near the Milky Way's SMBH. The star IRS 3 is in this field. It's an AGB star, and researchers are studying it to investigate the connection between material cast off from these types of stars and the interstellar medium. The researchers were surprised to find water and dust here, even though powerful radiation from the SMBH inhibit them. Image Credit: ESA/Webb, NASA & CSA, F. Peißker, J. Lu, F. Yusef-Zadeh, N. B. Sabha, C. Chan. Licence: CC BY 4.0 INT or ESA Standard Licence

The Milky Way's galactic center is dominated by its supermassive black hole (SMBH) Sagittarius A-star (Sgr. A*). It doesn't just dominate with its massive gravititional pull. It also overpowers the region with radiation that should destroy dust and other molecules.

New research shows that water and dust exist around a star near Sgr. A*. These materials were shed from a star near the SMBH, and they exist there despite the overwhelming radiation coming from the SMBH.

The star is named IRS 3, and it's a highly-evolved AGB star only about 0.55 light years from the massive SMBH. The star has about 6 solar masses and is about 72 million years old. Astronomers are interested in the connection between these stars and the interstellar medium (ISM). AGB stars can lose up to 70% of their mass during this phase, and that material has a powerful effect on the composition of the ISM.

In new research published in Astronomy and Astrophysics, astronomers used the JWST to observe IRS 3 and the area around it. Their work is titled "Dust production in the harsh environment of Sgr A*," and the lead author is Florian Peißker. Peißker is a post-doctoral researcher in the Institute of Physics at the University of Cologne in Germany.

"Studies of the interstellar medium (ISM) have frequently revealed signatures of the dust produced in the envelopes of asymptotic giant branch (AGB) stars, demonstrating a connection between the dust composition of the ISM and that of AGB stellar envelopes," the researchers write. "Investigating this relationship in the extreme, radiation-dominated environment surrounding Sgr A*, the center of our own galaxy, reveals how such conditions might influence dust composition and the recycling of material in galactic centers."

The Milky Way's galactic center is known for the intense radiation coming from Sgr. A*, including powerful x-ray flaring and gamma radiation. The researchers used the JWST's NIRCam to image the region, and its Mid-Infrared Instrument (MIRI) and its medium resolution spectrometer to study IRS3. "We aim to conduct a comprehensive spectral analysis to more tightly constrain the dust composition and line-emitting species within the envelope of IRS 3 in the immediate vicinity of Sgr A*," the researchers write.

This is a mid-infrared image of the region around IRS 3 from the research. A yellow × marks the SMBH Sgr A, and IRS 3 is labelled inside its callout box. The distance between Sgr A* and IRS 3 is about 0.17 parsecs. "The emission from IRS 3 is dominated by the extended envelope of the AGB star," the authors explain. Image Credit: Peißker et al. 2026. A&A.*

To their surprise, they found that alumina and amorphous silicates are present in the dust. They also found water, another surprise. "For the first time, we find clear signs of water in the envelope of IRS 3," they write.

“Galactic centres are among the most extreme environments, so understanding whether stars can continue enriching their surroundings there is an important question,” said lead author Peißker in a press release. “With Webb, we can directly observe how stars behave under these conditions and see that dust production remains remarkably resilient.”

Astronomers' interest in IRS 3 goes back decades. It's one of the brightest mid-IR sources in the galactic center, and the researchers describe it as the "most prominent AGB star within the inner parsec of the Milky Way." The star sits inside a massive gaseous cocoon that extends an estimate 10,000 astronomical units. Based on the JWST's spectroscopic data, the star's dusty envelope has a shell-like distribution shaped by a temperature gradient. The temperature changes from approximately 1200 Kelvin close to the star, to about 100 Kelvin in the outer regions.

AGB stars shape the ISM's composition with the types of dust they inject into it. "Analysis of the MIRI MRS spectrum reveals the presence of amorphous silicates, Al2O3, and H2O," the authors write.

But the amount of dust matters, too, and the researchers studied the star's bow shock to determine IRS 3's mass loss rate. They determined that it's shedding about 20 Earth masses per year, or one Earth mass every 18 days. They say that this is "characteristic of the superwind phase of an O-rich AGB star."

This image from the research shows the estimated stand-off distance between the IRS 3 and its bow shock. "The stand-off distance is a measure of the ambient ISM and the ram pressure of the star," the authors explain. Understanding this distance helps the researchers determine the star's mass loss rate. In this image, the green x marks the position of IRS 3 and the green circle marks the apex of the bow shock. Image Credit: Peißker et al. 2026. A&A.

“This discovery was possible because of Webb’s highly capable infrared instruments,” said Macarena Garcia Marin of ESA, a co-author of the study and PI of the MICONIC programme. “This is the first time a continuous mid-infrared spectrum has been collected for this star, allowing us to detect the features from the silicate dust and uncover the star’s true chemical identity.”

“The detection of water is especially exciting because it shows that molecular material can survive in an environment dominated by intense radiation,” said Macarena. “This tells us that even close to a supermassive black hole, stars can continue contributing material back into their surroundings.”

By Evan Gough - August 18, 2026 08:03 PM UTC | Stars

Source: Universe Today

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Evan Gough

Evan Gough is a science-loving guy with no formal education who loves Earth, forests, hiking, and heavy music. He's guided by Carl Sagan's quote: "Understanding is a kind of ecstasy."

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