STScI Scientists Surprised to Find Brightness ‘Gap’ in Ancient Star Cluster

Euclid image of NGC 6397

This Euclid image of globular cluster NGC 6397 is speckled with hundreds of thousands of stars, which vary in size and color. Most stars are located at the cluster’s center, where they are bound together by gravity. Scientists studying NGC 6397 found that when they grouped the cluster’s stars by brightness and color they observed a thin brightness “gap” of expected but missing low-mass stars called red dwarfs. This gap is thought to be linked to changes occurring within some stars’ interiors. This is the first time the gap feature was discovered in a globular cluster.Credits Image: ESA, NASA, Euclid Consortium - Image Processing: Jean-Charles Cuillandre (CEA-Saclay), Giovanni Anselmi (ESA)

Globular Cluster NGC 6397 Brightness "Gap" Feature

This graph shows the brightness gap that scientists found using Euclid when they grouped the globular cluster NGC 6397’s stars by brightness and color. What they observed was a thin “gap” of expected but missing low-mass stars called red dwarfs. The observations fit well with their model prediction. This gap is thought to be linked to changes occurring within some stars’ interiors, giving astronomers a glimpse at processes happening inside stars even from thousands of light-years away. This is the first time the gap feature was discovered in a globular cluster. Credits Illustration: Massimo Griggio (STScI), Leah Hustak (STScI)

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Scientists from the Space Telescope Science Institute (STScI) in Baltimore, Maryland, sought to study one stellar subject and ended up finding something even more exciting.

Using data from the European Space Agency’s (ESA’s) Euclid space telescope and NASA’s Hubble Space Telescope, the team planned to analyze the motions of stars within an ancient collection of stars called a globular cluster. But what they found when they grouped the cluster’s stars by brightness and color as observed by Euclid was a thin “gap” of expected but missing low-mass stars called red dwarfs. This gap is thought to be linked to changes occurring within some stars’ interiors, giving astronomers a glimpse at processes happening inside stars even from thousands of light-years away.

This is the first time the gap feature was discovered in a globular cluster. “The discovery was serendipitous,” said STScI’s Andrea Bellini, one of the research paper’s primary authors. “We were not looking for the gap, but we found it.”

Understanding the Gap

The presence of this gap in relatively nearby stars was discovered in 2018 by scientists analyzing data from ESA’s Gaia observatory. That team plotted nearly 250,000 stars from the Gaia archive on a Hertzsprung-Russell (HR) diagram, one of the most important tools in stellar studies. This is the graph that astronomers use to classify stars and trace their life cycles.

On the HR diagram, stellar luminosities are plotted against their colors, which serve as a proxy for their temperatures. The positions of stars on the diagram reveal specific stellar evolutionary stages. Perhaps the most distinctive feature is the swath of main-sequence stars that cuts diagonally across the diagram.

As the precision and sensitivity of modern astronomy improves, astronomers can place stars more accurately on the plot. The Gaia data revealed a previously unknown feature — a narrow, diagonal slice of mostly missing stars through the main sequence in the middle of the red dwarf region.

So what causes this gap? It appears that in some red dwarf stars, fuel built up in their centers can trigger an energy burst that results in structural instability in a star’s interior. Between 0.34 and 0.36 times the mass of the Sun, red dwarfs undergo small variations that change their size, brightness, and temperature. Because only a small number of stars are undergoing these changes, there is a dearth of red dwarfs with these specific brightnesses. This is reflected in the HR diagram as a gap.

Enabling More Accurate Distance Estimates

In the Gaia case, stars were at a multitude of different distances and had varying ages, histories, and chemical compositions. In contrast, stars within a globular cluster share a common history, having formed in the same environment at roughly the same point in cosmic time.

“Globular clusters are the ideal laboratories to study stellar evolution and stellar populations,” said STScI’s Massimo Griggio, the principal author on the research paper. “In this globular cluster, the stars are basically at the same distance and have approximately the same age.”

The STScI team used Euclid to study NGC 6397, one of the closest globular clusters to Earth. Located approximately 8,000 light-years away in the southern constellation Ara, it contains hundreds of thousands of stars and is estimated to be 13.4 billion years old.

“Because we can determine the brightness where the gap is with very high precision and know for what stellar masses it occurs, we can use this information to estimate the cluster’s distance,” said STScI’s Russell Ryan, another of the primary researchers.

Gaia found the gap while viewing stars in the local neighborhood, which are typically younger than stars in globular clusters. Now, the Euclid team found the exact same process happening in more distant stellar interiors.

Hubble Tools Pave the Way for New Discoveries

This finding would not have been possible without the software and techniques originally developed at STScI for NASA’s Hubble Space Telescope over more than two decades. The team used these tools, which were pioneered primarily by STScI’s Jay Anderson, to make the high-precision measurements needed to detect this feature in the extremely crowded environment of a globular cluster. Though Hubble’s field of view is much, much smaller, when these tools were coupled with Euclid’s panoramic view, the gap clearly appeared.

“With these tools, we show that we can push the limits of Euclid, and in the future, the Roman Space Telescope, across a wide field of view,” said team member Mattia Libralato, formerly of STScI and currently with the Italian National Institute for Astrophysics (INAF) in Padova, Italy.  “Further investigations with Euclid and, in the future, Roman, will hopefully allow us to better characterize this feature also in other globular clusters.”

The team’s results published today in Astronomy & Astrophysics.

The Space Telescope Science Institute is expanding the frontiers of space astronomy by hosting the science operations center of the Hubble Space Telescope, the science and mission operations centers for the James Webb Space Telescope, and the science operations center for the Nancy Grace Roman Space Telescope. STScI also houses the Barbara A. Mikulski Archive for Space Telescopes (MAST) which is a NASA-funded project to support and provide to the astronomical community a variety of astronomical data archives, and is the data repository for the Hubble, Webb, Roman, Kepler, K2, TESS missions and more. STScI is operated by the Association of Universities for Research in Astronomy in Washington, D.C.

Source: Space Telescope Science Institute (STScI)/News

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About This Release

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Media Contacts:

Ann Jenkins
Space Telescope Science Institute, Baltimore

Christine Pulliam
Space Telescope Science Institute, Baltimore

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Related Links and Documents

Euclid: Early Release Observations – Internal kinematics and the convective-transition gap of NGC 6397

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Spiral Galaxy NGC 4045

NGC 4045
Credit: NAOJ; Image provided by Masayuki Tanaka

Detail: Low Res. ( 69 KB) / Mid. Res. ( 978 KB) / High Res. ( 7.5 MB)

The spiral galaxy NGC 4045, located in the Virgo constellation, displays two distinct spiral arms extending from its bright central nucleus to its outer regions. A faint blue spiral arm stretches to the right, indicating that stars are actively forming in the outer regions of this galaxy.Below NGC 4045 lies another galaxy, NGC 4045 A. Although it appears close enough to be gravitationally interacting with NGC 4045, it is actually a far more distant galaxy aligned along the same line of sight from Earth, and the two galaxies are not physically associated.

Source: Subaru Telescope

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Is this Be star isolated?

Artists impression of “edge-on” view of a Be star with ioniozed gas disk.
Credit: NASA/ESA/G. Bacon (STScI)
Download Image

During the past week, NuSTAR observed CL Pismis 17 3, hitherto known as an isolated Be star, that shows suspiciously strong X-ray emission above 3 keV. This is part of a campaign to probe such anomalously X-ray bright Be stars for hidden accreting companions, like a neutron star, or possibly a white dwarf. The NuSTAR data is crucial to determine if the system is undergoing active mass transfer, as the hard X-ray spectrum is a reliable probe for Comptonised emission, as expected from an accreting neutron star. In such a case, the system would join a growing list of Be X-ray binaries, that are known to be accreting persistently at a stable lower luminosity, instead of being punctuated by very luminous outbursts as they typically exhibit. This not only allows us to sharpen constraints on the X-ray luminosity function of High Mass X-ray Binaries, which are crucial to understand our Galactic star formation history, but also provides us with a test case to study persistent but tenuous accretion mechanisms.

Author: Aafia Ansar Mohideen (Research Scientist, Dr. Karl Remeis Sternwarte Astronomical Institute, Germany)

Source: NASA's Nuclear Spectroscopic Telescope Array (NuSTAR)/Weekly Highlights

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Red dwarf stars detected 'eating' Earth-like planets

This artist's impression shows two Earth-sized worlds passing in front of their parent red dwarf star in the TRAPPIST-1 system 40 light-years away. Credit: ESA/Hubble

Licence type: Attribution (CC BY 4.0)

Astronomers have found some of the strongest evidence yet that stars can swallow their own planets.

A new study, published in Monthly Notices of the Astronomical Society, supports the long-held belief that young stars are capable of 'eating' nearby worlds as planetary systems form.

Researchers from Keele University and the University of Exeter studied thousands of stars and found evidence that six different red dwarfs – the smallest, coolest, and most common type of star in the universe – had engulfed Earth-like rocky planets.

What gave it away was the highly detectable chemical 'fingerprint', said lead author Professor Robin Jeffries, from Keele University.

"We found that a few of the red dwarf stars we studied contained lithium, a chemical element that should not be there," he explained.

"Therefore even a small amount of lithium stands out clearly in these stars – a bit like throwing paint onto a blank canvas."

Professor Jeffries added: "Red dwarfs are smaller and cooler than our Sun but inside they are extremely hot. This heat should destroy all of their fragile lithium in nuclear reactions shortly after they form."

Because of this, there have been previous predictions that finding the presence of lithium in their atmospheres could signpost the engulfment of still lithium-rich material accreted from a surrounding planetary system.

In the new study, the researchers looked at young star clusters using spectroscopic data, which refers to the study of how different matter interacts with electromagnetic radiation.

The Gaia-ESO Spectroscopic (GES) survey data covered thousands of stars, of which the team identified six different red dwarfs in three separate clusters which had much higher lithium content than other stars of a similar spectral type.

Their analysis suggests that these stars had dramatically ‘swallowed’ their surrounding Earth-like planets, or about 3 to 10 Earth-masses of planetary material in total, providing a fresh burst of lithium to their otherwise lithium-depleted atmospheres.

These engulfment events have long been theorised as a possible and even probable outcome during early planetary system formation, and may even have happened earlier in our own Solar System.

If this explanation proves correct, a new window will have been opened into the early lives of planetary systems, allowing the quantity and timing of planetary engulfment to be investigated.

Unlike isolated stars, those found in clusters have well-understood ages and masses, and the presence of many similar siblings, born from the same initial material, means even small chemical abundance differences are easier to establish, the researchers said.

Source: Royal Astronomical Society (RAS)/Latest News.

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Media contacts:

Sam Tonkin
Royal Astronomical Society
Mob: +44 (0)7802 877 700
press@ras.ac.uk

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Science contacts:

Professor Robin Jeffries
Keele University
r.d.jeffries@keele.ac.uk

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Images & captions

Red dwarf

Caption: This artist's impression shows two Earth-sized worlds passing in front of their parent red dwarf star in the TRAPPIST-1 system 40 light-years away.

Credit: ESA/Hubble

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Further information

The paper ‘Lithium-rich M-dwarfs at the ZAMS: evidence for planetary engulfment?’ by Jeffries et al. has been published in Monthly Notices of the Royal Astronomical Society. DOI: 10.1093/mnras/stag815.

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Notes for editors

About the Royal Astronomical Society

The Royal Astronomical Society (RAS), founded in 1820, encourages and promotes the study of astronomy, solar-system science, geophysics and closely related branches of science.

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

The RAS accepts papers for its journals based on the principle of successful peer review, following which experts on the Editorial Boards accept the papers for publication. The Society issues press releases based on a similar principle, but the organisations and scientists concerned have overall responsibility for their content.

Keep up with the RAS on Instagram,Bluesky, LinkedIn, Facebook and YouTube.

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Submitted by Sam Tonkin on Thu, 28/05/2026 - 12:58

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Strange Winds Reveal Strongest Hints Yet of Magnetic Activity in Exoplanets

PR Image noirlab2614a
Artist’s illustration of hot Jupiter with magnetic field

PR Image noirlab2614b
Circumpolar Laser Tests at Gemini North

PR Image noirlab2614c
MAROON-X at Gemini North

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Cosmoview Episodio 109: Vientos extremos revelan señales de campos magnéticos en exoplanetas
in English only

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Using the Gemini North telescope in Hawai‘i and the European Southern Observatory’s Very Large Telescope, a team of astronomers measured wind speeds on seven very hot, Jupiter-like exoplanets. The observations revealed that the winds on these planets are most likely governed by magnetic fields, providing the first robust measurement of magnetic activity on planets outside the Solar System.

By measuring the strength of the invisible magnetic fields of seven ultra-hot Jupiters, astronomers have taken a major step toward understanding planets beyond our Solar System. A new study published today in Nature Astronomy reveals hints that the magnetic fields of some of the hottest known exoplanets are similar in strength to those of planets in our own Solar System.

“This breakthrough opens a completely new window on exoplanet research. It’s the first time we can compare the magnetic environments of other worlds — a key step toward ultimately understanding which planets can stay alive, keep their water, and perhaps even, one day, host life as we know it,” says Julia Seidel, an astronomer at the Laboratoire Lagrange, Observatoire de la Côte d’Azur, France, and lead author of the study.

Earth's magnetic field acts as a shield: it helps stop cosmic radiation from stripping away our atmosphere, keeping the planet habitable for life. Magnetic fields are also present on other Solar System planets, like Jupiter and Saturn. However, no one succeeded in directly measuring the strength of the magnetic fields of planets outside of our Solar System — until now.

The team, however, didn’t set out to measure magnetic fields but, rather, winds. They measured wind speeds on seven exoplanets orbiting different stars: gas giants like Jupiter, but each tidally locked to its host star and very close to it. Just as we always see only one side of the Moon from Earth, these planets always keep one side facing their host star, resulting in a scorching-hot day side and a freezing-cold night side. This temperature difference creates a climate completely different from the one on our planet, with extremely strong winds. The wind speeds in their sample ranged from around 7200 kilometers (4400 miles) per hour to over 25,000 kilometers (15,500 miles) per hour; in comparison, the fastest winds measured on Jupiter reach speeds of around 1500 kilometers (900 miles) per hour.

For their measurements, the team used data from the MAROON-X instrument on the Gemini North telescope in Hawaiʻi, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab. They also used data from the ESPRESSO instrument on ESO’s VLT in the Chilean Atacama Desert. These powerful, high-resolution instruments allowed the team to measure wind speeds by detecting the light signature of specific chemicals and tracing their movements through the ultra-hot Jupiters’ atmospheres.

“The stability of MAROON-X makes it a powerful tool for detecting the subtle motion of Earth-sized planets around other stars, as well as tracing changes in the atmospheres of exoplanets depending on orbital phase,” says Andreas Seifahrt, Associate Director of Development for Gemini Observatory and study co-author. “The unexpected discovery that resulted from studying the winds of these seven ultra-hot Jupiters shows that there is even more that we can learn from the data. MAROON-X provides a world-class capability for these studies.”

When the researchers looked at how wind speeds varied with the planet’s temperature, they saw a very intriguing pattern emerge: the hotter the planet, the slower the wind. “This is totally counterintuitive because, all things being equal, hot planets have more energy to accelerate the winds! Something must happen that slows down the wind speeds for hotter objects,” says study co-author Vivien Parmentier, a professor at the Laboratoire Lagrange.

The team concluded that the most consistent explanation for this mystery is the presence of planet-wide magnetic fields, since these fields can work as a brake, slowing down the motion of charged particles in the atmosphere. The data, therefore, allowed the researchers to infer the strength of the magnetic field of each of the studied planets. They found them to be comparable in strength to those found in our Solar System: approximately four times as strong as Saturn’s magnetic field or about half the strength of Jupiter’s.

Such strong magnetic fields could affect more than just the wind on these distant planets. “Here on Earth, we know the beauty of the northern and southern lights, where particles from the Sun hit our magnetic field and are guided toward the poles, colliding with gases in the atmosphere to produce colourful displays of green, pink, and purple,” explains study co-author Bibiana Prinoth, a former PhD student at Lund University, Sweden, now an astronomer at ESO in Garching, Germany. On the studied exoplanets, the magnetically driven aurorae could be even more dramatic.

Source: NSF’s National Optical-Infrared Astronomy Research Laboratory (NOIRLab)/News

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More information

This research was presented in a paper titled “Magnetic field strengths of hot giant exoplanets consistent with Solar System values” to appear in Nature Astronomy. DOI: 10.1038/s41550-026-02870-1

The team is composed of J. V. Seidel (European Southern Observatory, Chile; Université Côte d’Azur, France), V. Parmentier (Université Côte d’Azur, France), B. Prinoth (Lund University, Sweden; European Southern Observatory, Germany), et al.

NSF NOIRLab, the U.S. National Science Foundation center for ground-based optical-infrared astronomy, operates the International Gemini Observatory (a facility of NSF, NRC–Canada, ANID–Chile, MCTIC–Brazil, MINCyT–Argentina, and KASI–Republic of Korea), NSF Kitt Peak National Observatory (KPNO), NSF Cerro Tololo Inter-American Observatory (CTIO), the Community Science and Data Center (CSDC), and NSF–DOE Vera C. Rubin Observatory (in cooperation with DOE’s SLAC National Accelerator Laboratory). It is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with NSF and is headquartered in Tucson, Arizona.

The scientific community is honored to have the opportunity to conduct astronomical research on I’oligam Du’ag (Kitt Peak) in Arizona, on Maunakea in Hawai‘i, and on Cerro Tololo and Cerro Pachón in Chile. We recognize and acknowledge the very significant cultural role and reverence of I’oligam Du’ag to the Tohono O’odham Nation, and Maunakea to the Kanaka Maoli (Native Hawaiians) community.

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

• Read the paper: Magnetic field strengths of hot giant exoplanets consistent with Solar System values
• ESO press release
• Photos of the Gemini North telescope
• Videos of the Gemini North telescope
• Check out other NOIRLab Science Releases
• For journalists: subscribe to receive our releases under embargo
• For scientists: got a story? Pitch your research

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Contacts:

Julia Victoria Seidel
Lagrange Laboratory, Observatoire de la Côte d'Azur
Nice, France
Tel: +33 743 32 79 73
Email: jseidel@oca.eu

Josie Fenske
Public Information Officer
NSF NOIRLab
Email: josie.fenske@noirlab.edu

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Dropping Dark Matter from the Pisa Tower: A New Test of the Equivalence Principle with the Distortion of Time in Galaxy Clusters

A sketch of the Pisa tower on top of the Perseus cluster of galaxies observed by the Euclid satellite. Background image: ESA/Euclid/Euclid Consortium/NASA, image processing by J.-C. Cuillandre (CEA Paris-Saclay), G. Anselmi.

All types of ordinary matter fall in a gravitational potential in the same way, while dark matter may experience deviations. The depth of the gravitational potential can be measured through the impact of the time distortion on light, which changes frequency and hence colour in escaping the potential to reach an observer. © MPA

Predicted precision on deviations from the weak equivalence principle as a function of the total number of galaxies in galaxy clusters used to perform the test. The vertical line indicates the number used in the first detection of the distortion of time. The different colours correspond to more or less optimistic assumptions on the other free parameters involved in the test, ranging from assuming perfect knowledge of their values (black) to no knowledge (green).© MPA

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Does the mysterious dark matter experience gravity in the same way as ordinary matter? A team of scientists from MPA and the University of Geneva (Switzerland) has developed a new method to answer this question by measuring the time dilation in galaxy clusters. With future datasets, this method could detect violations of the equivalence principle at the level of a few percent.

In the 16th century, the Italian scientist Galileo Galilei is said to have dropped objects with different masses from the Leaning Tower of Pisa. With this experiment – possibly only imagined – he demonstrated that the acceleration of different bodies does not depend on their composition or mass. Since then, this seemingly counter-intuitive fact has become a fundamental pillar in our understanding of gravity, known as the weak equivalence principle. This principle states that any particle, regardless of its nature, experiences gravity in the same way.

Several experiments have confirmed with very high precision that the weak equivalence principle holds for all particles making up the ordinary matter around us. However, astrophysical and cosmological observations indicate that around 85 % of the matter in the Universe consists of unknown dark matter, which does not emit light and can only be probed through its gravitational impact on visible matter. If Galileo could have thrown a small amount of dark matter from the Pisa tower, would it have experienced the same acceleration as the other bodies? This remains a crucial open question, which could help shedding light on the nature of this mysterious component.

A team of researchers from MPA and the University of Geneva (Switzerland) – Sveva Castello, Enea Di Dio and Camille Bonvin – is determined to answer this question. Since dark matter has never been detected directly nor produced in a laboratory experiment, it is not possible to simply drop it from the Pisa tower. However, the team has designed a new method to perform an analogous experiment to Galileo’s in galaxy clusters. These are the largest gravitationally bound objects in the Universe and therefore provide the ideal environment to study the behaviour of dark matter under gravity. The new test consists in comparing the observed motion of the galaxies inside the clusters with the distortion of time generated by the clusters themselves.

Understanding the idea behind this test requires a small detour to the realm of Einstein’s theory of general relativity, providing our modern understanding of gravity. According to general relativity, the Universe can be described as a four-dimensional spacetime that gets distorted like a tablecloth in the presence of any object with a mass, such as galaxy clusters. This generates gravitational potential wells, which determine the motion of any particle under gravity. These distortions affect not only space but also time, so that a clock located at the bottom of a potential well ticks more slowly than one outside of it. This effect, known as time dilation or distortion of time, provides a direct measure of the depth of the gravitational potential well generated by a massive object.

If dark matter violates the weak equivalence principle, for example due to some unknown interactions, its motion under gravity will be different from the one predicted by general relativity. Since galaxies are mostly composed of dark matter, such a violation will impact their observed velocities inside a cluster. They will then move too fast or too slowly compared to the gravitational potential well of the cluster inferred from the distortion of time, clearly indicating an anomaly. Therefore, comparing galaxy velocities and the distortion of time in a galaxy cluster provides a powerful test of the weak equivalence principle.

Since we cannot send clocks across cosmological distances, how can we measure the distortion of time in galaxy clusters located billions of light-years away? This can be achieved by considering the impact of the distortion of time on light. Due to this effect, the wavelength of light emitted by galaxies in a cluster gets stretched and experiences a frequency shift, which is translated into a change of its observed colour. This leads to an observable gravitational redshift, which can be disentangled from other effects that change the colour of the light thanks to its symmetry properties when considering pairs of galaxies. This technique led to a first detection of this effect in 2011 by Radosław Wojtak, Steen H. Hansen and Jens Hjorth, who used a catalogue of around 100’000 galaxies in clusters by the Sloan Digital Sky Survey.

In this new study, the MPA-Geneva team predicted that existing measurements of the distortion of time can detect deviations from the weak equivalence principle at the level of 7-14 %. Ongoing galaxy surveys, such as the Euclid satellite and the Dark Energy Spectroscopic Instrument (DESI), will give access to larger samples of galaxy clusters and thus lead to an increased precision. In a realistic scenario, future datasets will be sensitive to violations of the equivalence principle at the level of a few percent.

As a next step, the team plans to apply the test to data. This will enable them to repeat Galileo’s experiment on astrophysical scales, providing crucial information on the properties of the mysterious dark matter in galaxy clusters. The discovery of a violation of the weak equivalence principle would have profound implications for cosmology, astrophysics and particle physics, and may also affect our fundamental understanding of gravity.

Source: Max Planck Institute for Astrophysics/Research Highlights

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Author:

Dr. Sveva Castello
Postdoc
Tel: 2007
Email: svevacas@mpa-garching.mpg.de

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Strange winds reveal strongest hints yet of magnetic activity in exoplanets

PR Image eso2606a
Artist’s impression of an exoplanet with a magnetic field

PR Image eso2606b
How magnetic fields govern winds in exoplanets

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Strange winds reveal magnetic exoplanets | ESO News


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Animation of an exoplanet with a magnetic field


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How magnetic fields govern winds in exoplanets

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A team of astronomers has found the strongest evidence yet that some planets outside our Solar System may be magnetic. Using the European Southern Observatory’s Very Large Telescope (ESO's VLT) and the Gemini North telescope, the researchers measured wind speeds on seven very hot, Jupiter-like exoplanets. The observations revealed that the winds on these planets are most likely governed by magnetic fields, providing the first robust measurement of magnetism on planets outside the Solar System.

“This breakthrough opens a completely new window on exoplanet research. It’s the first time we can compare the magnetic environments of other worlds — a key step toward ultimately understanding which planets can stay alive, keep their water, and perhaps even, one day, host life as we know it,” says Julia Seidel, an astronomer at the Laboratoire Lagrange, Observatoire de la Côte d’Azur, France and lead author of the study published today in Nature Astronomy.

Earth’s magnetic field influences our atmosphere in complex ways, and is therefore a key factor in understanding what keeps the planet habitable for life. Magnetic fields are also present in other Solar System planets, like Jupiter and Saturn. However, for the past 15 years, no one succeeded in directly measuring the strength of the magnetic fields of exoplanets — until now.

The team, however, didn’t set out to measure magnetic fields but, rather, winds. They measured wind speeds on seven exoplanets orbiting different stars: gas giants like Jupiter, but each tidally locked to its host star and very close to it. Just as we always see only one side of the Moon, these planets always keep one face towards the star, resulting in a scorching hot day side and a freezing cold night side. This temperature difference creates a climate completely different from the one on our planet, with extremely strong winds. The wind speeds in their sample ranged from around 7200 km/h to over 25 000 km/h; in comparison, the fastest winds measured on Jupiter reach speeds of around 1500 km/h.

“In the beginning we set out to check if the atmospheric winds behaved the same way for all hot planets,” explains Seidel, who was previously an astronomer at ESO in Chile. For their measurements, the team used data from the ESPRESSO instrument on ESO’s VLT, in the Chilean Atacama Desert, and from a similar instrument on the Gemini North telescope in Hawaiʻi, USA. (The VLT is an ESO telescope while Gemini North is one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab.)

But when they looked at how the wind speeds varied with planet temperature, they saw a very intriguing pattern emerge: the hotter the planet, the slower the wind. “This is totally counter intuitive because, all things being equal, hot planets have more energy to accelerate the winds! Something must happen that slows down the wind speeds for hotter objects,” says study co-author Vivien Parmentier, a professor at the Laboratoire Lagrange.

The team concluded that the most consistent explanation for this mystery is the presence of planet-wide magnetic fields, since these fields can work as a brake, slowing down the motion of charged particles in the atmosphere. The data therefore allowed the researchers to infer the strength of the magnetic field in each of the studied planets. They found them to be comparable in strength to those found in our Solar System: approximately four times as strong as Saturn's or about half the strength of Jupiter's.

Such strong magnetic fields could affect more than just the wind on these distant planets. "Here on Earth, we know the beauty of the northern and southern lights, where particles from the Sun hit our magnetic field and are guided toward the poles, colliding with gases in the atmosphere to produce colourful displays of green, pink, and purple," explains study co-author Bibiana Prinoth, a former PhD student at Lund University, Sweden, now an astronomer at ESO in Garching, Germany. On the studied exoplanets, the magnetically driven aurorae could be even more dramatic. The team eagerly anticipates the arrival of ESO’s Extremely Large Telescope, which will help to characterise not only large, Jupiter-like exoplanets but also smaller ones like Earth, possibly even detecting gases that could produce aurorae on these distant worlds. Prinoth says: “I like to imagine that some of these worlds have a sky filled not only with stars, but with vast curtains of colourful light dancing across a planet that’s half in perpetual day and half in endless night.”

Source: ESO/News

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More information

This research was presented in a paper to appear in Nature Astronomy (doi:10.1038/s41550-026-02870-1).

The team is composed of Julia V. Seidel (European Southern Observatory, Santiago, Chile [ESO Chile]; Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, France [Lagrange]), Vivien Parmentier (Lagrange), Bibiana Prinoth (Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Lund, Sweden[LU]), Thea Hood (Lagrange), Nishil Mehta (Lagrange), Valentin De Lia (Lagrange), Brian Thorsbro (Lagrange, LU), Konstantin Batygin (Division of Geological and Planetary Sciences, California Institute of Technology, USA), Tristan Guillot (Lagrange), Ragnar van den Broeck (Lagrange), Florian Debras (IRAP, Université de Toulouse, Toulouse, France), Daniel D. B. Koll (School of Physics, Peking University), Thaddeus Komacek (Department of Physics (Atmospheric, Oceanic and Planetary Physics), University of Oxford, Oxford, UK [Oxford]), Hayley Beltz (Department of Astronomy, University of Maryland, College Park, USA), Emily Rauscher (Department of Astronomy and Astrophysics, University of Michigan, MI, USA), Lorenzo Pino (INAF - Osservatorio Astrofisico di Arcetri, Florence, Italy), Matteo Brogi (Dipartimento di Fisica, Università di Ferrara, Ferrara, Italy; INAF – Osservatorio Astrofisico di Torino, Turin, Italy), Joost P. Wardenier (Département de Physique, Institut Trottier de Recherche sur les Exoplanètes, Université de Montréal, Canada [iREx]), Jacob L. Bean (Department of Astronomy & Astrophysics, University of Chicago, Chicago, USA [Chicago]), Björn Benneke (iREx and Department of Earth, Planetary, and Space Sciences, University of California, Los Angeles, CA 90095, USA), Jean-Michel L. B. Desert (Anton Pannekoek Institute for Astronomy, University of Amsterdam, Amsterdam, Netherlands), Pablo Drake (Lagrange), Siddharth Gandhi (Department of Physics, University of Warwick, Coventry, UK and Centre for Exoplanets and Habitability, University of Warwick, Coventry, UK), Mark Hammond (Oxford), David Kasper (Chicago), Michael R. Line (School of Earth and Space Exploration, Arizona State University, Tempe, USA [SESE]), Elspeth Lee (Center for Space and Habitability, niversity of Bern, Bern, Switzerland), Stefan Pelletier (Observatoire astronomique de l’Université de Genève, Versoix, Switzerland), Andreas Seifahrt (International Gemini Observatory/NSF NOIRLab, Tucson, USA), Adrien Simonnin (Lagrange), Peter Smith (SESE), and Kevin B. Stevenson (JHU Applied Physics Laboratory, Laurel, USA)

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
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• For scientists: got a story? Pitch your research

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Contacts:

Julia Victoria Seidel
Lagrange Laboratory, Observatoire de la Côte d'Azur
Nice, France
Tel: +33 743 32 79 73
Email: jseidel@oca.eu

Vivien Parmentier
Lagrange Laboratory, Observatoire de la Côte d'Azur
Nice, France
Email: Vivien.PARMENTIER@univ-cotedazur.fr

Bibiana Prinoth
European Southern Observatory (ESO)
Garching bei München, Germany
Email: bibiana.prinoth@eso.org

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

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Simulations Explain Baby Carriage Wheels Around Baby Stars

Left: Observations of a star-forming region with a hub-and-spoke shape like a baby carriage wheel. Right: A similar shape produced by a simulation using the ATERUI III supercomputer. (Credit: M. S. N. Kumar, ESA/Herschel, NASA/JPL-Caltech (Spitzer), S. Nozaki, S. Inutsuka) Image (716KB)

Numerical simulation of the formation of a hub–filament system molecular cloud.

After an interstellar shock wave passes through a molecular cloud, multiple filaments characteristic of a hub–filament system develop radially toward the center. The left panels show the cloud viewed perpendicular to the propagation direction of the interstellar shock wave, while the right panels show the view parallel to the direction from which the shock wave approaches. The numbers in the upper left indicate the elapsed time since the start of the simulation. Note that the right panels are displayed using a different density range than the left panels in order to make the higher-density gas easier to distinguish. (Credit: Shingo Nozaki (Kyushu University))

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Research using multiple supercomputers, including ATERUI III at the National Astronomical Observatory of Japan, has found a possible explanation for the hub-and-spoke pattern seen in some molecular clouds where baby stars are forming. According to the new numerical simulations, if an external shock interacts with magnetic fields which have been warped by the motion of the clouds, gas can be channeled into a shape resembling the spokes on the wheels of a baby carriage.

When parts of molecular clouds become dense enough, they can collapse under self-gravity. As a result of this collapse, the gas in the clouds condenses into protostars which will grow into stars. For this reason, molecular clouds are nicknamed “stellar cradles.” But some of these sites of star formation are more like baby carriages than cradles because they have filaments of gas extending toward a central hub, forming a shape like a spoked wheel.

Researchers from Kyushu University and Nagoya University investigated the possibility that magnetic fields within the clouds might play a role in forming this distinct shape. Using ATERUI III, a dedicated-astronomy supercomputer operated by the National Astronomical Observatory of Japan, they modeled how gas and magnetic fields evolve together over time. The results show that as the cloud collapses under self-gravity, it pulls the magnetic field lines inward, bending them into an hourglass shape. The team then simulated the effects of a disturbance like a shock wave from a nearby supernova remnant or from expanding gas around a massive star. The team found that if this shock hits the curved magnetic field at certain angles, it strengthens parts of the magnetic field, forming invisible channels that guide compressed gas into long, narrow filaments converging toward the center.

The team now plans to conduct more simulations to test whether this mechanism can explain more asymmetric and complex shapes. This will help clarify how the diversity of observed hub-filament systems reflects differences in cloud environments and how such environments shape the formation of massive stars and clusters.

Source: National Astronomical Observatory of Japan (NAOJ)/News

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Detailed Article(s)

Simulations Explain Baby Carriage Wheels Around Baby Stars
Center for Computational Astrophysics

Release Information

Researcher(s) Involved in this Release

Shingo Nozaki (Kyushu University)
Shu-ichiro Inutsuka (Nagoya University)

Coordinated Release Organization(s)

Kyushu University
Nagoya University
National Astronomical Observatory of Japan, NINS

Paper(s)

Shingo Nozaki and Shu-ichiro Inutsuka “An Origin of Radially Aligned Filaments in Hub-filament Systems”, in Astrophysical Journal Letters, DOI: 10.3847/2041-8213/ae4c84

Related Link(s)

Scientists show how baby stars' cradles get their radial shape (Kyushu University)

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Hubble spies faint irregular galaxy ESO 490-017

This NASA Hubble Space Telescope image captures the faint glow of the dwarf irregular galaxy ESO 490-017.
Credit: NASA, ESA, R. Tully (University of Hawaii); Image Processing: G. Kober (NASA/Catholic University of America)

This NASA Hubble Space Telescope image features the dwarf irregular galaxy ESO 490-017, roughly 12,000 light-years in diameter and some 23 million light-years away in the constellation Canis Major. The galaxy's low surface brightness makes it appear as a faint, starry swarm behind brighter foreground stars that are easily recognized by their diffraction spikes. Numerous red, orange, and beige dots are distant galaxies peppering the black background, many exhibiting distinct spiral structure.

The data in this image of ESO 490-017 was part of a Hubble observing program that looked at the movement of galaxies and galaxy clusters through space. Matter in the universe is distributed unevenly, and the gravitational influence of that matter drives the "cosmic flow" or movement of large-scale structures in the universe.

Hubble is uniquely capable of providing distances to nearby galaxies like ESO 490-017 by measuring the luminosities of low-mass red giant stars as "standard candles." The observing program also provided a legacy archive of the types of stars in local galaxies.

Provided  by Claire Andreoli,  NASA

edited by Gaby Clark, reviewed by Robert Egan

Source: Phys.org/News

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Explore further

Hubble captures galaxy cluster MACS J1141.6-1905

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NASA’s Webb Reveals Black Hole That Formed Before Its Galaxy

Little Red Dot Abell2744-QSO1 (NIRCam Image)

An image from NIRCam on NASA’s James Webb Space Telescope shows Little Red Dot Abell2744-QSO1, magnified and triply imaged by galaxy cluster Abell 2744 (Pandora’s Cluster). Credit Image: NASA, ESA, CSA, Lukas Furtak (Ben-Gurion University); Image Processing: Alyssa Pagan (STScI)

Little Red Dot Abell2744-QSO1a (NIRCam Image with NIRSpec IFU Velocity Map)

An image detail from NIRCam (left) on NASA’s James Webb Space Telescope shows Little Red Dot Abell2744-QSO1. A map of gas velocity in QSO1 (right), made using the IFU on NIRSpec, shows evidence for a 50-million-solar-mass black hole at the center. Credit Image: NASA, ESA, CSA, Ignas Juodžbalis (Cambridge), Cosimo Marconcini (University of Florence), Roberto Maiolino (Cambridge), Francesco D'Eugenio (Cambridge), Hannah Übler (MPE); Image Processing: Alyssa Pagan (STScI)

Little Red Dot Abell2744-QSO1 (NIRCam Compass Image)

Image of Abell 2744 and Little Red Dot Abell2744-QSO1, captured by Webb’s NIRCam, with compass arrows, scale bar, and color key for reference. Credit Image: NASA, ESA, CSA, Lukas Furtak (Ben-Gurion University); Image Processing: Alyssa Pagan (STScI)

Little Red Dot Abell2744-QSO1: Sonification of Gas Velocity Around a Supermassive Black Hole (NIRCam and NIRSpec IFU)

A sonification is a translation of data into sound. In this sonification, the velocity of hydrogen gas moving around a black hole in the center of a Little Red Dot known as Abell2744-QSO1 (QSO1) is translated into sounds of varying pitch (or frequency). The faster the gas is moving toward the telescope, the higher the pitch. The faster it is moving away from the telescope, the lower the pitch. Credit Sonification: NASA, ESA, CSA, STScI, Christopher Britt (STScI), Ralf Crawford (STScI), Alyssa Pagan (STScI), Margaret Carruthers (STScI); Science: Ignas Juodžbalis (Cambridge), Cosimo Marconcini (University of Florence), Roberto Maiolino (Cambridge), Francesco D'Eugenio (Cambridge), Hannah Übler (MPE)

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Which comes first, the galaxy or the black hole? We don’t know, but scientists have long thought it could be the galaxy: Large stars within an existing galaxy consume their fuel and collapse to form black holes, which can gobble up surrounding material and merge over time to form more massive entities.

But it’s hard to figure out how black holes millions to billions of times the mass of the Sun, thousands of which have now been detected in the early universe, could have grown so quickly from such small seeds.

Now, researchers using NASA’s James Webb Space Telescope have detected clear evidence that some supermassive black holes were enormous from the beginning, forming without a stellar collapse phase, and without a significantly more massive host galaxy to feed them.

“This is a remarkable finding,” said Roberto Maiolino of University of Cambridge in the United Kingdom, co-author of studies published in Nature and the Monthly Notices of the Royal Astronomical Society. “It’s a paradigm shift, a total revisiting of the classical scenarios of how black holes form and grow.”

Little Red Dot QSO1

The team’s conclusion is based on detailed observations of Abell2744-QSO1 (QSO1), a prototypical Little Red Dot that existed just 700 million years after the big bang.

Although QSO1 is only 1,300 light-years across, and its light has been traveling for more than 13 billion years, it is easier to study than most other Little Red Dots because it is gravitationally lensed by galaxy cluster Abell 2744 (Pandora’s Cluster). QSO1 is both magnified and triply imaged, appearing in three different locations in the sky.

Initial studies of QSO1 revealed compelling evidence that it may be little more than a cloud of glowing hydrogen and helium gas circling a supermassive black hole estimated at 40 million times the mass of the Sun. But as with other early black holes discovered by Webb, there was uncertainty about whether it really was that massive. “Before now, all of the mass measurements of black holes in the early universe have been indirect, based on assumptions from what we know about them in the local universe. We didn’t know if those assumptions really apply to the distant universe,” said co-author Francesco D’Eugenio, also of the University of Cambridge.

Mapping gas composition, velocity

The team recognized that if QSO1’s black hole is as massive as it looks, they should be able to use the integral field unit (IFU) on Webb’s NIRSpec (Near Infrared Spectrograph) to trace the effects of its gravity on the gas swirling around it, while also mapping the distribution of various elements in the gas.

Cambridge graduate student Ignas Juodžbalis and Cosimo Marconcini of the University of Florence, lead authors on one of the studies, used the IFU observations to map motions of hydrogen gas surrounding the black hole. When they plotted the rotation velocity as a function of distance from the center, they found that the gas has Keplerian motion: It orbits a central point in the same way that planets in our solar system orbit the Sun.

“This is important because it tells us that most of the mass of QSO1 is concentrated in the black hole at the center,” said Juodžbalis. “If the mass were more distributed, as it would be if there were a lot of stars, the gas would not have this perfect Keplerian rotation.”

Since Keplerian motion is governed by simple laws of gravity, the team was able to use the gas velocity measurements to calculate the black hole mass directly, a feat that had not previously been possible.

They found that not only is the black hole immense — roughly 50 million solar masses — it makes up, at minimum, an astonishing two-thirds of QSO1’s total mass. This proportion is thousands of times greater than in nearby galaxies, where supermassive black holes make up only a tiny fraction of the host galaxy’s total mass.

The IFU composition maps supported these results, showing that the gas throughout QSO1 is almost entirely hydrogen and helium, with very little of the heavier elements like oxygen that would be expected in a galaxy rich with stars and stellar debris. With a metallicity less than 0.5% of the Sun, QSO1 is one of the most pristine galactic environments ever measured.

“This is a phenomenal result,” said Maiolino. “It is the first direct measurement of a black hole mass within the first billion years after the big bang, and it is consistent with the previous measurements.” The team thinks this is a good sign that the assumptions used for indirect mass measurements are valid and the masses of other black holes in the early universe have not been overestimated.

Supermassive black hole origins

The team recognized that if QSO1’s black hole is as massive as it looks, they should be able to use the integral The outsized mass of QSO1 relative to its host galaxy suggests that it can’t have formed gradually from much smaller, stellar-mass black holes merging and feeding. “It seems that we have found a black hole that does not have a substantial host galaxy and that has predated stellar processes,” said Juodžbalis. “This is very exciting because it is evidence for primordial black holes or direct collapse black holes, which have been theorized but not confirmed.”

Whether QSO1’s black hole evolved from a “heavy seed” that formed within the first second of the big bang or somewhat later from the collapse of a giant cloud of gas, it was almost certainly born big, and may be in the early stages of building a galaxy around it.

The team thinks that Little Red Dots like QSO1 cannot have been rare in the early universe, and is in the process of analyzing similar objects to find out whether supermassive black holes actually do predate the galaxies where they currently reside.

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

Source: NASA's James Webb Space Telescope/Latest News

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Related Links

Watch: NASA Black Hole Visualization Takes Viewers Beyond the Brink

Explore more: ViewSpace | Black Holes: Searching for the unseen

Read more: Dissecting Supermassive Black Holes

Watch: What Webb Learns from Light

Explore more: NASA's Universe of Learning: Black Hole Resources

More Webb News

More Webb Images

Webb Science Themes

Webb Mission Page

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I Spy with My Large Binocular Eyes: A Dusty Torus Around a Supermassive Black Hole?

Hubble Space Telescope image of the active galaxy NGC 4151.
Credit: NASA, ESA, Joseph DePasquale (STScI)

Title: Shocks, Winds, and a Torus: The Large Binocular Telescope Interferometer (LBTI) Resolves the Active Nucleus of NGC 4151

Authors: Jacob W. Isbell et al.
First Author’s Institution: University of Arizona
Status: Published in ApJ

At the centre of nearly every galaxy lies a supermassive black hole that dominates this innermost region. Not only is there this millions-of-solar-masses dark beast, but usually too a whole bunch of stuff — stars, gas, dust, and more — which is often quite bright! When there is plenty of this material quite close to the black hole, we believe physics takes control to flatten it into a family of disk and toroidal structures in what we call the unified model of active galactic nuclei (AGNs; see Figure 1).

Figure 1: The unified model of AGNs asserts that there is an inner accretion disk, surrounded by a dusty torus that cohabitates with clouds moving at different velocities (the so-called broad and narrow line regions), and sometimes even relativistic jets extending from the accretion disk to galactic scales; you can read more about AGN structure in this Astrobites guide. Credit:  Emma Alexander; CC BY 4.0

When astronomers look at different active galaxies (read: galaxies with active supermassive black holes at their core), we see a range of phenomenologies related to their brightness, spectra, morphologies, and more. The unified model of AGNs seeks to explain these different AGN appearances simultaneously by positing that they all have the same physical structure, and we are just viewing them from different angles, hence seeing different features.

The cores of AGNs are often imaged at the smallest scales (e.g., their accretion disks, viewed with interferometers like the Very Large Telescope Interferometer) and the largest scales (e.g., their relativistic jets, viewed with radio interferometers), but comparatively less effort has gone to directly observing the predicted dusty tori in the mid-infrared. That is exactly what today’s authors set out to do using the Large Binocular Telescope Interferometer (LBTI) — a pair of 8.4-metre-aperture mirrors separated by just over 14 metres and combined to simulate a telescope effectively 29 metres wide. This lets astronomers take direct images at a much higher resolution than a smaller-aperture telescope, and hence directly peer into the region around AGNs where this dusty torus should lie.

Today’s authors turn the LBTI towards NGC 4151, a medium-luminosity AGN. With the large effective aperture of the LBTI, they were able to resolve scales in the AGN region as small as 4.4–9.1 pc, about 14–30 light-years depending on the wavelength (see Figure 2), in the mid-infrared. These observations revealed warm dust emission in a complex structure around the central supermassive black hole. The authors note a central bar at all wavelengths, with a significant extension of cool dust arcing to the west (right in the image) and warmer dust localised to the centre (as evident by 3.7- and 4.8-micron emission only nearest to the supermassive black hole and its accretion disk).

Figure 2: The deconvolved images of the AGN core of NGC 4151 show a very bright central source (the innermost region around the supermassive black hole), as well as some complex surrounding structure particularly at long wavelengths. The interpreted morphology is described in Figure 3. These images are deconvolved, meaning that known optical effects are corrected for on the raw data to produce a sharper image. Adapted from Isbell et al. 2026

To explain the observed morphology in Figure 1, the authors compare three different interpretations based on this new high-resolution imagery together with the results of previous studies looking at other scales and the spectrum of the AGN core. Each interpretation is illustrated and briefed in Figure 3.

Figure 3: Three interpretations of the observed morphology are presented by the authors. The left panel illustrates the different regions surrounding the supermassive black hole (together with the results of other studies cited in the article). The right panel shows the suggested interpretations explaining the morphology. Credit: Isbell et al. 2026

The first interpretation is in keeping with the unified model of AGNs: a geometrically and optically thick torus of dust surrounds the inner region. In this interpretation, the surface of the dusty torus re-radiates light from the accretion disk to produce most of the mid-infrared emission. Additional mid-infrared emission could come from localised concentrations of gas or interactions between the outflow and the jet. The authors immediately disfavour this explanation, as other studies have shown bright ionised emission at the location of the would-be torus, which is not expected if an optically thick torus were to be present. Hence, these new observations somewhat challenge the one “flavour” of the unified model of AGNs.

The second interpretation aligns with a different version of the unified model: one in which a geometrically thin disk replaces a thick torus around the AGN core. Provided the disk is optically thin too, the authors favour this approach as it is consistent with the geometry of ionised emission that worked against the first interpretation. While other studies suggest that this thin disk should be optically thick, this morphology is at least better aligned with what we see in other AGNs.

The third interpretation suggests that the emission comes from only the radiation pressure–driven wind emanating from the AGN core. The authors disfavour this explanation, citing previous radiative transfer simulations that show that the flux should fall off with distance from the core too quickly to be consistent with the observations.

No matter the interpretation, these LBTI observations are an important glimpse into the future of mid-infrared AGN studies that will be done with 30-metre-class telescopes (such as the European Southern Observatory’s Extremely Large Telescope). This article, together with the group’s similar study on NGC 1068, is challenging and refining an accepted view of AGN morphology — the consequences of which apply to galaxies near and far — and poses new questions perfect for sophisticated hydrodynamic and radiative simulations.

Original astrobite edited by Margaret Verrico.

Source: American Astronomical Society/AAS-Nova

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About the author, Ryan White:

I am a first-year PhD student at Macquarie University in Australia, working mainly on binary/multiple systems with massive stars (Wolf–Rayets in particular!). Outside of study, I’m probably drinking coffee, baking, reading, or going for a run. You can also find me procrastinating on Bluesky @astroryan.bsky.social.

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

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