NASA Webb Explores Effect of Strong Magnetic Fields on Star Formation

Milky Way Center (MeerKAT and Webb)

Credits/Image: NASA, ESA, CSA, STScI, SARAO, Samuel Crowe (UVA), John Bally (CU), Ruben Fedriani (IAA-CSIC), Ian Heywood (Oxford)

Milky Way Center (MeerKAT and Webb), Labeled

Credits/Image: NASA, ESA, CSA, STScI, SARAO, Samuel Crowe (UVA), John Bally (CU), Ruben Fedriani (IAA-CSIC), Ian Heywood (Oxford)

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Follow-up research on a 2023 image of the Sagittarius C stellar nursery in the heart of our Milky Way galaxy, captured by NASA’s James Webb Space Telescope, has revealed ejections from still-forming protostars and insights into the impact of strong magnetic fields on interstellar gas and the life cycle of stars.

“A big question in the Central Molecular Zone of our galaxy has been, if there is so much dense gas and cosmic dust here, and we know that stars form in such clouds, why are so few stars born here?” said astrophysicist John Bally of the University of Colorado Boulder, one of the principal investigators. “Now, for the first time, we are seeing directly that strong magnetic fields may play an important role in suppressing star formation, even at small scales.”

Detailed study of stars in this crowded, dusty region has been limited, but Webb’s advanced near-infrared instruments have allowed astronomers to see through the clouds to study young stars like never before.

“The extreme environment of the galactic center is a fascinating place to put star formation theories to the test, and the infrared capabilities of NASA’s James Webb Space Telescope provide the opportunity to build on past important observations from ground-based telescopes like ALMA and MeerKAT,” said Samuel Crowe, another principal investigator on the research, a senior undergraduate at the University of Virginia and a 2025 Rhodes Scholar.

Bally and Crowe each led a paper published in The Astrophysical Journal.

Using Infrared to Reveal Forming Stars

In Sagittarius C’s brightest cluster, the researchers confirmed the tentative finding from the Atacama Large Millimeter Array (ALMA) that two massive stars are forming there. Along with infrared data from NASA’s retired Spitzer Space Telescope and SOFIA (Stratospheric Observatory for Infrared Astronomy) mission, as well as the Herschel Space Observatory, they used Webb to determine that each of the massive protostars is already more than 20 times the mass of the Sun. Webb also revealed the bright outflows powered by each protostar.

Even more challenging is finding low-mass protostars, still shrouded in cocoons of cosmic dust. Researchers compared Webb’s data with ALMA’s past observations to identify five likely low-mass protostar candidates.

The team also identified 88 features that appear to be shocked hydrogen gas, where material being blasted out in jets from young stars impacts the surrounding gas cloud. Analysis of these features led to the discovery of a new star-forming cloud, distinct from the main Sagittarius C cloud, hosting at least two protostars powering their own jets.

“Outflows from forming stars in Sagittarius C have been hinted at in past observations, but this is the first time we’ve been able to confirm them in infrared light. It’s very exciting to see, because there is still a lot we don’t know about star formation, especially in the Central Molecular Zone, and it’s so important to how the universe works,” said Crowe.

Magnetic Fields and Star Formation

Webb’s 2023 image of Sagittarius C showed dozens of distinctive filaments in a region of hot hydrogen plasma surrounding the main star-forming cloud. New analysis by Bally and his team has led them to hypothesize that the filaments are shaped by magnetic fields, which have also been observed in the past by the ground-based observatories ALMA and MeerKAT (formerly the Karoo Array Telescope).

“The motion of gas swirling in the extreme tidal forces of the Milky Way’s supermassive black hole, Sagittarius A*, can stretch and amplify the surrounding magnetic fields. Those fields, in turn, are shaping the plasma in Sagittarius C,” said Bally.

The researchers think that the magnetic forces in the galactic center may be strong enough to keep the plasma from spreading, instead confining it into the concentrated filaments seen in the Webb image. These strong magnetic fields may also resist the gravity that would typically cause dense clouds of gas and dust to collapse and forge stars, explaining Sagittarius C’s lower-than-expected star formation rate.

“This is an exciting area for future research, as the influence of strong magnetic fields, in the center of our galaxy or other galaxies, on stellar ecology has not been fully considered,” said Crowe.

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/News

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About This Release

Credits:

Media Contact:

Leah Ramsay
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
Space Telescope Science Institute, Baltimore, Maryland

Permissions: Content Use Policy

Related Links and Documents

• The JWST-NIRCam View of Sagittarius C. I. Massive Star Formation and Protostellar Outflows
• The JWST-NIRCam View of Sagittarius C. II. Evidence for Magnetically Dominated HII Regions in the Central Molecular Zone
• The CU Boulder Press Release

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A galaxy that gives great feedback

NGC 4941

A spiral galaxy seen at a diagonal angle. Its very centre is a bright white glowing orb, surrounded by an inner disc of golden light. This is wrapped in a broad outer disc that glows more dimly, with patchy, broken spiral arms swirling around it, filled with small blue and pink star clusters. Dark reddish threads of dust also spiral through the disc, with some strands reaching into the core. Credit: ESA/Hubble & NASA, D. Thilker

This NASA/ESA Hubble Space Telescope Picture of the Week features the picturesque spiral galaxy NGC 4941, which lies about 67 million light-years from Earth in the constellation Virgo (The Maiden). Because this galaxy is nearby, cosmically speaking, Hubble’s keen instruments are able to pick out exquisite details such as individual star clusters and filamentary clouds of gas and dust.

The data used to construct this image were collected as part of an observing programme that investigates the star formation and stellar feedback cycle in nearby galaxies. As stars form in dense, cold clumps of gas, they begin to influence their surroundings. Stars heat and stir up the gas clouds in which they are born through winds, starlight, and — eventually, for massive stars — by exploding as supernovae. These processes are collectively called stellar feedback, and they impact the rate at which a galaxy can form new stars.

As it turns out, stars aren’t the only entities providing feedback in NGC 4941. At the heart of this galaxy lies an active galactic nucleus: a supermassive black hole feasting on gas. As the black hole amasses gas from its surroundings, the gas swirls into a superheated disc that glows brightly at wavelengths across the electromagnetic spectrum. Similar to stars — but on a much, much larger scale — active galactic nuclei shape their surroundings through winds, radiation, and powerful jets, altering not only star formation but also the evolution of the galaxy as a whole.

Source: ESA/Hubble/potw

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Spying a spiral through a cosmic lens

In the centre is an elliptical galaxy, seen as an oval-shaped glow around a small bright core. Around this is wrapped a broad band of light, appearing like a spiral galaxy stretched and warped into a ring, with bright blue lines drawn through it where the spiral arms have been stretched into circles. A few distant objects are visible around the ring on a black background. Credit: ESA/Webb, NASA & CSA, G. Mahler. Acknowledgement: M. A. McDonald

This new NASA/ESA/CSA James Webb Space Telescope Picture of the Month features a rare cosmic phenomenon called an Einstein ring. What at first appears to be a single, strangely shaped galaxy is actually two galaxies that are separated by a large distance. The closer foreground galaxy sits at the center of the image, while the more distant background galaxy appears to be wrapped around the closer galaxy, forming a ring.

Einstein rings occur when light from a very distant object is bent (or ‘lensed’) about a massive intermediate (or ‘lensing’) object. This is possible because spacetime, the fabric of the Universe itself, is bent by mass, and therefore light travelling through space and time is bent as well. This effect is much too subtle to be observed on a local level, but it sometimes becomes clearly observable when dealing with curvatures of light on enormous, astronomical scales, such as when the light from one galaxy is bent around another galaxy or galaxy cluster.

When the lensed object and the lensing object line up just so, the result is the distinctive Einstein ring shape, which appears as a full circle (as seen here) or a partial circle of light around the lensing object, depending on the precision of the alignment. Objects like these are the ideal laboratory in which to research galaxies too faint and distant to otherwise see.

The lensing galaxy at the center of this Einstein ring is an elliptical galaxy, as can be seen from the galaxy’s bright core and smooth, featureless body. This galaxy belongs to a galaxy cluster named SMACSJ0028.2-7537. The lensed galaxy wrapped around the elliptical galaxy is a spiral galaxy. Even though its image has been warped as its light travelled around the galaxy in its path, individual star clusters and gas structures are clearly visible.

The Webb data used in this image were taken as part of the Strong Lensing and Cluster Evolution (SLICE) survey (programme 5594), which is led by Guillaume Mahler at University of Liège in Belgium, and consists of a team of international astronomers. This survey aims to trace 8 billion years of galaxy cluster evolution by targeting 182 galaxy clusters with Webb’s Near-InfraRed Camera instrument. This image also incorporates data from two of the NASA/ESA Hubble Space Telescope’s instruments, the Wide Field Camera 3 and the Advanced Camera for Surveys.

Links

• Pan Video: Einstein ring in galaxy cluster SMACSJ0028.2-7537
• Image on ESA website

Source: ESA/Webb/potm

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A New Cosmic Ruler: Measuring the Hubble Constant with Type II Supernovae

Figure 1: Type II supernova sample used for the Hubble constant measurement. The images show the host galaxies of the ten supernovae, with the explosion sites marked by red star symbols. The images are aligned with a redshift scale reflecting the relative distances of the supernovae from Earth. © MPA

Figure 2: Spectral fitting and the Hubble diagram for Type II supernovae. The top panels show two examples of spectral fits used to determine the supernova distances. By comparing observed spectra (black) with model predictions (colour), researchers can extract key physical properties and infer the intrinsic brightness, enabling a direct distance measurement. The bottom panel presents a Hubble diagram, where the measured luminosity distances of the supernovae are plotted against their redshifts. The data points represent individual spectral observations, meaning multiple measurements can exist for each supernova. The dashed black line represents the best-fit relationship between distance and redshift, and its slope is determined by the Hubble constant. The grey-shaded regions indicate the uncertainties for this fit (68% and 95% confidence intervals). The best-fit value for the Hubble constant and its 68% confidence interval are H₀ = 74.9 ± 1.9 km/s/Mpc. © MPA

Figure 3: Artist’s impression of the Hubble tension, showing the two different approaches to measuring the Hubble constant as two bridges that do not quite connect. The depicted early-Universe measurements yield an average value of 67.4 km/s/Mpc, the local measurements an average value of 73.0 km/s/Mpc. The new measurement from this study, based on Type II supernovae (orange), is completely independent of all other measurements and provides compelling support for the Hubble tension. The local route also includes results from various incarnations of the cosmic distance ladder, as well as other direct methods such as gravitational lensing and water masers. Image Credit: Original image by NOIRLab/NSF/AURA/J. da Silva, sourced from NOIRLab (CC BY 4.0), modified by S. Taubenberger.

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The expansion rate of the Universe, quantified by the Hubble constant (H₀), remains one of the most debated quantities in cosmology. Measurements based on nearby objects yield a higher value than those inferred from observations of the early Universe—a discrepancy known as the "Hubble tension". Researchers at the Max Planck Institute for Astrophysics and their collaborators have now presented a new, independent determination of H₀ using Type II supernovae. By modeling the light from these exploding stars with advanced radiation transport techniques, they were able to directly measure distances without relying on the traditional distance ladder. The resulting H₀ value agrees with other local measurements and adds to the growing body of evidence for the Hubble tension, offering an important cross-check and a promising path toward resolving this cosmic puzzle.

One of the biggest puzzles in modern cosmology is the ongoing discrepancy in measurements of the Hubble constant (H₀) between local and early Universe probes, known as the “Hubble tension”. Since H₀ describes the current expansion rate of the Universe, it is a local quantity and can only be directly measured using nearby objects. In contrast, methods based on the early Universe, such as those using the cosmic microwave background (CMB), do not measure H₀ directly. Instead, they infer its value by assuming a cosmological model to extrapolate from the conditions 13 billion years ago to today. The fact that these two approaches yield conflicting values—with local distance-ladder measurements giving a higher H₀ than early-Universe methods—suggests that our standard cosmological model may be incomplete, potentially pointing to new physics.

Researchers at the Max Planck Institute for Astrophysics (MPA) and their collaborators have explored an independent way of measuring H₀ using Type II supernovae (SNe II). Unlike traditional approaches, this method does not rely on the cosmic distance ladder, making it a powerful cross-check against existing techniques. Their results provide a new, highly precise measurement of H₀ and further contribute to the debate over the expansion rate of the Universe.

Determining the Hubble constant requires accurate measurements of distances to astronomical objects at different redshifts. The most widely used technique, the cosmic distance ladder, relies on several interconnected steps: distances to nearby objects (such as Cepheid variable stars) are used to calibrate further reaching indicators such as Type Ia supernovae (SNe Ia), which then serve as standard candles to measure distances to faraway galaxies.

However, the reliance on multiple steps introduces possible systematic uncertainties, and different teams report slightly different results. A direct measurement based on known physics offers a valuable complementary approach, as it is affected by different systematics and does not depend on empirical calibrations. This is where Type II supernovae provide an exciting alternative.

Type II supernovae occur when massive, hydrogen-rich stars explode at the end of their lives. While their brightness varies depending on factors such as temperature, expansion velocity, and chemical composition, it can be accurately predicted using radiation transport models. This allows researchers to determine their intrinsic luminosity and use them as distance indicators, independent of empirical calibration methods.

A critical step in this process is identifying the best-fitting model for each observed supernova. Key physical properties leave distinct imprints on the supernova spectrum: temperature shapes the overall continuum, expansion velocity sets the width of spectral lines via Doppler broadening, and chemical composition determines the strength of specific absorption and emission features. By systematically comparing observed spectra to simulated spectra from radiative transfer models, researchers can find the model that most accurately describes the supernova’s physical conditions. With such a well-matched model the intrinsic brightness—and thus the distance—can be precisely determined.

To make this process efficient, the team used a spectral emulator, an advanced machine-learning tool trained on precomputed simulations. Instead of running time-intensive radiation transport calculations for every supernova, the emulator rapidly interpolates between models, allowing for fast and accurate spectral fitting.

The research team applied their spectral modeling approach to a sample of ten Type II supernovae at redshifts between 0.01 and 0.04, using publicly available data not specifically designed for distance measurements (Fig. 1). Despite the limitations of the dataset, their method yielded reliable distances. By constructing a Hubble diagram from these measurements (Fig. 2), they obtained an independent estimate of H₀: H₀ = 74.9 ± 1.9 km/s/Mpc

This value is consistent with most other local measurements, such as those from Cepheid-calibrated supernovae and supports the tension with early-Universe probes. The achieved precision is comparable to the most competitive techniques, demonstrating that Type II supernovae are a promising tool for cosmology (Fig. 3).

This study serves as a proof of concept, showing that Type II supernovae can provide precise and reliable distance measurements in the Hubble flow. Future work will focus on increasing the sample size and improving the accuracy of the technique by using dedicated observations. To this end, the researchers have assembled the adH0cc dataset (https://adh0cc.github.io/), a collection of Type II supernova observations from the ESO Very Large Telescope, specifically designed for precise distance measurements. This dataset will serve as a key resource for refining the method. By providing an independent check on the local determination of H₀, Type II supernovae help astrophysicists tackle one of the most pressing questions in cosmology today: Is the Hubble tension real, and if so, what does it tell us about the fundamental nature of the Universe?

Source: Max Planck Institute for Astrophysics/Research Highlights

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Authors:

Christian Vogl
Postdoc
2297
cvogl@mpa-garching.mpg.de

Stefan Taubenberger
2019
tauben@mpa-garching.mpg.de

Wolfgang Hillebrandt
Emeritus Director

Original publication

Vogl, Christian; Taubenberger, Stefan; et al.
No rungs attached: A distance-ladder free determination of the Hubble constant through type II supernova spectral modelling
submitted to A&A

Source

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CfA Scientists Play Important Role in New NASA Mission

This artist's impression of SPHEREx shows the spacecraft as it will appear when in low-Earth orbit. During its 27-month nominal mission, SPHEREx will conduct four all-sky surveys to study the early history of the cosmos and search for interstellar molecules such as water and other compounds thought to be precursors of life as we know it.  Credit: NASA/JPLM High Resolution Image

A new NASA mission with major roles from scientists at the Center for Astrophysics | Harvard & Smithsonian (CfA) will help answer questions about why the large scale structure of the Universe looks the way it does today, how galaxies form and evolve, and what are the abundances of water and other key ingredients for life in our Galaxy.

SPHEREx (Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer) will identify specific atoms and molecules in millions of objects across space using their unique signatures in optical and infrared spectra, which show how their light depends on wavelength.

After its launch into space on March 11, 2025 from the Vandenberg Space Force Base in California, SPHEREx will survey the entire sky four times over its 25-month mission. Astronomers will be able to combine SPHEREx’s ability to scan large sections of the sky quickly with more targeted studies Harvard-Smithsonian Center for Astrophysics (CfA) from ground-based telescopes and others in space like NASA’s James Webb Space Telescope (JWST).

The CfA will lead the investigation into the abundances and distributions of molecules that are vital for life. Specifically, SPHEREx will conduct a survey along almost 10 million lines of sight in the Milky Way and the Magellanic Clouds, neighboring galaxies to our own. This survey will reveal crucial life-enabling molecules like water (H₂O), carbon monoxide (CO), and carbon dioxide (CO₂) in their icy states on the surfaces of interstellar dust grains.

These data will enable CfA scientists to evaluate the ice content in each direction and will help to trace the evolution of these ices as they transition from molecular clouds to planet-forming disks and, ultimately, to newly forming planets.  JWST can follow up the most interesting targets identified by SPHEREx, making the two facilities a particularly powerful combination for studying how Solar System planets as well as planets around other stars get their key ingredients for life.

The CfA SPHEREx team is led by Dr.Gary Melnick and includes Drs. Matthew Ashby, Joseph Hora, and Volker Tolls, who are joined by visiting scientist, Dr. Jaeyeong Kim, from the Korean Astronomy and Space Science Institute.

SPHEREx’ data will be freely available to scientists around the world, providing new information about hundreds of millions of cosmic objects. More about SPHEREx at the CfA can be found at https://www.cfa.harvard.edu/facilities-technology/telescopes-instruments/spherex

Source: Harvard-Smithsonian Center for Astrophysics (CfA)/News

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Investigating Neutron Star Evolution

An artist's impression of a neutron-star X-ray binary accreting from its companion star and powering a jet.
Image credit: NASA/JPL-Caltech/R. Hurt (SSC)
Download Image

Over the past week, NuSTAR has conducted an intensive observing campaign on the neutron star X-ray binary GX 340+0, in coordination with the Australian Telescope Compact Array (ATCA, radio) and the X-ray Telescope aboard NASA’s Gehrels-Swift observatory. This well-known system belongs to the so-called "Z-source" family – a group of bright, accreting neutron stars that persistently trace a distinctive "Z-shaped" pattern in diagrams of their X-ray "hardness" (or color) plotted against their X-ray intensity. As these systems move back and forth along this Z-shaped track, typically over a timescale of about a week, their X-ray spectral and timing properties undergo a clear evolution. However, this evolution is significantly less pronounced compared to most other X-ray binaries, whether they contain neutron stars or black holes as the central accreting object. Interestingly, despite the relatively subtle changes in their X-ray properties, the radio emission from Z-sources has been observed to vary dramatically depending on their position along the Z-track. This suggests that the physical properties of their radio jets evolve far more than the underlying accretion flow. This behavior is unexpected, as such dramatic jet evolution is typically accompanied by equally dramatic changes in X-ray spectral-timing properties – especially in black hole systems. This discrepancy raises the possibility of different jet-launching mechanisms, distinct physical conditions, and/or unique correlations between jets and accretion flows in neutron star versus black hole X-ray binaries. To investigate this intriguing scenario, six simultaneous NuSTAR and ATCA observations were coordinated with a near-daily cadence over the course of a week. This observing strategy will, for the first time, track the co-evolution of the jet (radio) and accretion flow (X-rays) in this system, providing unique and unprecedented insights into the factors that govern jet evolution in Z-sources.

Authors: Alessio Marino (Postdoctoral fellow, ICE-CSIC, Spain)

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

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Famed WR 104 “Pinwheel” Star Reveals Another Surprise (and Some Relief)

An artist’s concept of the famous Wolf-Rayet 104 “pinwheel star,” previously nicknamed the “Death Star.” New research conducted from Maunakea, Hawaiʻi using three Keck Observatory instruments reveals the orbit of the two stars are angled 30 or 40 degrees away from us, sparing Earth from a potential gamma-ray burst (GRB). Credit: W. M. Keck Observatory/Adam Makarenko

An artist’s animation of WR 104, first discovered at Keck Observatory in 1999. It consists of two stars orbiting each other; a Wolf-Rayet star that produces a powerful, carbon-rich wind (depicted in yellow), and an OB star that creates a wind mostly made of hydrogen (depicted in blue). When the winds collide, they whip up a hydrocarbon “dust” spiral. Credit: W. M. Keck Observatory/Adam Makarenko

An infrared image of WR 104 captured by Keck Observatory’s NIRC instrument in 1998
Credit: U.C. Berkeley Space Sciences Laboratory/W. M. Keck Observatory

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A new spin on decades of W. M. Keck Observatory research

Maunakea, Hawaiʻi – A recent study reveals the famous Wolf-Rayet 104 “pinwheel star” holds more mystery but is even less likely to be the potential ‘Death Star’ it was once thought to be.

Research by W. M. Keck Observatory Instrument Scientist and astronomer Grant Hill finally confirms what has been suspected for years: WR 104 has at its heart a pair of massive stars orbiting each other with a period of about 8 months and the collision between their powerful winds gives rise to its rotating pinwheel of dust that glows in the infrared, and spins with the same period.

The pinwheel structure of WR 104 was discovered at Keck Observatory in 1999 and the remarkable images of it turning in the sky astonished astronomers. One of the two stars that were suspected to orbit each other – a Wolf-Rayet star– is a massive, evolved star that produces a powerful wind highly enriched with carbon. The second star – a less evolved but even more massive OB star – has a strong wind that is still mostly hydrogen. Collisions between winds like these are thought to allow hydrocarbons to form, often referred to as “dust” by astronomers. When discovered, WR 104 also made headlines as a potential gamma-ray burst (GRB) that could be aimed right at us. Models of the pinwheel images indicated it was rotating in the plane of the sky as if we were looking directly down on someone spinning a streaming garden hose over their head. That could mean the rotational poles of the two stars might be pointed in our direction as well. When one of the stars ends its life as a supernova the explosion might be energetic enough to create a GRB that would beam in the polar directions. Since it is located right here in our own Galaxy, and seemed to be aimed right at us, at the time, WR 104 gained a second nickname – the ‘Death Star’.

Hill’s research, published in the Monthly Notices of the Royal Astronomical Society, is based on spectroscopy using three of Keck Observatory’s instruments – the Low Resolution Imaging Spectrometer (LRIS), the Echellette Spectrograph and Imager (ESI), and the Near-Infrared Spectrograph (NIRSPEC). With these spectra, he was able to measure velocities for the two stars, calculate their orbit and identify features in the spectra arising from the colliding winds. There turned out to be a very big surprise in store though.

“Our view of the pinwheel dust spiral from Earth absolutely looks face-on (spinning in the plane of the sky), and it seemed like a pretty safe assumption that the two stars are orbiting the same way” says Hill. “When I started this project, I thought the main focus would be the colliding winds and a face-on orbit was a given. Instead, I found something very unexpected. The orbit is tilted at least 30 or 40 degrees out of the plane of the sky.”

While a relief for those worried about a nearby GRB pointed right at us, this represents a real curveball. How can the dust spiral and the orbit be tilted so much to each other? Are there more physics that needs to be considered when modelling the formation of the dust plume?

“This is such a great example of how with astronomy we often begin a study and the universe surprises us with mysteries we didn’t expect” muses Hill. “We may answer some questions but create more. In the end, that is sometimes how we learn more about physics and the universe we live in. In this case, WR 104 is not done surprising us yet!”

Source: W.M. Keck ObservatoryScience News

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About NIRSPEC

The Near-Infrared Spectrograph (NIRSPEC) is a unique, cross-dispersed echelle spectrograph that captures spectra of objects over a large range of infrared wavelengths at high spectral resolution. Built at the UCLA Infrared Laboratory by a team led by Prof. Ian McLean, the instrument is used for radial velocity studies of cool stars, abundance measurements of stars and their environs, planetary science, and many other scientific programs. A second mode provides low spectral resolution but high sensitivity and is popular for studies of distant galaxies and very cool low-mass stars. NIRSPEC can also be used with Keck II’s adaptive optics (AO)system to combine the powers of the high spatial resolution of AO with the high spectral resolution of NIRSPEC. Support for this project was provided by the Heising-Simons Foundation.

About LRIS

The Low Resolution Imaging Spectrometer (LRIS) is a very versatile and ultra-sensitive visible-wavelength imager and spectrograph built at the California Institute of Technology by a team led by Prof. Bev Oke and Prof. Judy Cohen and commissioned in 1993. Since then it has seen two major upgrades to further enhance its capabilities: the addition of a second, blue arm optimized for shorter wavelengths of light and the installation of detectors that are much more sensitive at the longest (red) wavelengths. Each arm is optimized for the wavelengths it covers. This large range of wavelength coverage, combined with the instrument’s high sensitivity, allows the study of everything from comets (which have interesting features in the ultraviolet part of the spectrum), to the blue light from star formation, to the red light of very distant objects. LRIS also records the spectra of up to 50 objects simultaneously, especially useful for studies of clusters of galaxies in the most distant reaches, and earliest times, of the universe. LRIS was used in observing distant supernovae by astronomers who received the Nobel Prize in Physics in 2011 for research determining that the universe was speeding up in its expansion

About ESI

The Echellette Spectrograph and Imager (ESI) is a medium-resolution visible-light spectrograph that records spectra from 0.39 to 1.1 microns in each exposure. Built at UCO/Lick Observatory by a team led by Prof. Joe Miller, ESI also has a low-resolution mode and can image in a 2 x 8 arc min field of view. An upgrade provided an integral field unit that can provide spectra everywhere across a small, 5.7 x4.0 arc sec field. Astronomers have found a number of uses for ESI, from observing the cosmological effects of weak gravitational lensing to searching for the most metal-poor stars in our galaxy.

About W. M. KECK OBSERVATORY

The W. M. Keck Observatory telescopes are among the most scientifically productive on Earth. The two 10-meter optical/infrared telescopes atop Maunakea on the Island of Hawaii feature a suite of advanced instruments including imagers, multi-object spectrographs, high-resolution spectrographs, integral-field spectrometers, and world-leading laser guide star adaptive optics systems. Some of the data presented herein were obtained at Keck Observatory, which is a private 501(c) 3 non-profit organization operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the Native Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. For more information, visit: www.keckobservatory.org

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NASA's Webb Sees Galaxy Mysteriously Clearing Fog of Early Universe

JADES-GS-z13-1 in the GOODS-S field (NIRCam Image)

Credits/Image: NASA, ESA, CSA, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA), Joris Witstok (Cambridge, University of Copenhagen), P. Jakobsen (University of Copenhagen), Alyssa Pagan (STScI), Mahdi Zamani (ESA/Webb), JADES Collaboration

JADES-GS-z13-1 (NIRCam Close-Up)

Credits/Image: NASA, ESA, CSA, Brant Robertson (UC Santa Cruz), Ben Johnson (CfA), Sandro Tacchella (Cambridge), Phill Cargile (CfA), Joris Witstok (Cambridge, University of Copenhagen), P. Jakobsen (University of Copenhagen), Alyssa Pagan (STScI), Mahdi Zamani (ESA/Webb), JADES Collaboration

JADES-GS-z13-1 Spectrum Graphic

Credits/Illustration: NASA, ESA, CSA, S. Carniani (Scuola Normale Superiore), P. Jakobsen (University of Copenhagen), Joseph Olmsted (STScI)

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Using the unique infrared sensitivity of NASA’s James Webb Space Telescope, researchers can examine ancient galaxies to probe secrets of the early universe. Now, an international team of astronomers has identified bright hydrogen emission from a galaxy in an unexpectedly early time in the universe’s history. The surprise finding is challenging researchers to explain how this light could have pierced the thick fog of neutral hydrogen that filled space at that time.

The Webb telescope discovered the incredibly distant galaxy JADES-GS-z13-1, observed to exist just 330 million years after the big bang, in images taken by Webb’s NIRCam (Near-Infrared Camera) as part of the James Webb Space Telescope Advanced Deep Extragalactic Survey (JADES). Researchers used the galaxy’s brightness in different infrared filters to estimate its redshift, which measures a galaxy’s distance from Earth based on how its light has been stretched out during its journey through expanding space.

The NIRCam imaging yielded an initial redshift estimate of 12.9. Seeking to confirm its extreme redshift, an international team lead by Joris Witstok of the University of Cambridge in the United Kingdom as well as the Cosmic Dawn Center and the University of Copenhagen in Denmark, then observed the galaxy using Webb’s NIRSpec (Near-Infrared Spectrograph) instrument. In the resulting spectrum the redshift was confirmed to be 13.0. This equates to a galaxy seen just 330 million years after the big bang, a small fraction of the universe’s present age of 13.8 billion years old. But an unexpected feature stood out as well: one specific, distinctly bright wavelength of light, known as Lyman-alpha emission radiated by hydrogen atoms. This emission was far stronger than astronomers thought possible at this early stage in the universe’s development.

“The early universe was bathed in a thick fog of neutral hydrogen," explained Roberto Maiolino, a team member from the University of Cambridge and University College London. "Most of this haze was lifted in a process called reionization, which was completed about one billion years after the big bang. GS-z13-1 is seen when the universe was only 330 million years old, yet it shows a surprisingly clear, telltale signature of Lyman-alpha emission that can only be seen once the surrounding fog has fully lifted. This result was totally unexpected by theories of early galaxy formation and has caught astronomers by surprise.”

Before and during the era of reionization, the immense amounts of neutral hydrogen fog surrounding galaxies blocked any energetic ultraviolet light they emitted, much like the filtering effect of colored glass. Until enough stars had formed and were able to ionize the hydrogen gas, no such light — including Lyman-alpha emission — could escape from these fledgling galaxies to reach Earth. The confirmation of Lyman-alpha radiation from this galaxy, therefore, has great implications for our understanding of the early universe.

“We really shouldn’t have found a galaxy like this, given our understanding of the way the universe has evolved," said Kevin Hainline, a team member from the University of Arizona. "We could think of the early universe as shrouded with a thick fog that would make it exceedingly difficult to find even powerful lighthouses peeking through, yet here we see the beam of light from this galaxy piercing the veil. This fascinating emission line has huge ramifications for how and when the universe reionized.”

The source of the Lyman-alpha radiation from this galaxy is not yet known, but may include the first light from the earliest generation of stars to form in the universe. “The large bubble of ionized hydrogen surrounding this galaxy might have been created by a peculiar population of stars — much more massive, hotter and more luminous than stars formed at later epochs, and possibly representative of the first generation of stars," said Witstok. A powerful active galactic nucleus, driven by one of the first supermassive black holes, is another possibility identified by the team.

This research was published Wednesday in the journal Nature.

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/News

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Space Telescope Science Institute, Baltimore, Maryland

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• The science paper by J. Witstok et al.

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NASA's Webb Captures Neptune's Auroras For First Time

Neptune Auroras (Hubble and Webb Image)

Credits/Image: NASA, ESA, CSA, STScI, Heidi Hammel (AURA), Henrik Melin (Northumbria University), Leigh Fletcher (University of Leicester), Stefanie Milam (NASA-GSFC)

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For the first time, NASA’s James Webb Space Telescope has captured bright auroral activity on Neptune. Auroras occur when energetic particles, often originating from the Sun, become trapped in a planet’s magnetic field and eventually strike the upper atmosphere. The energy released during these collisions creates the signature glow.

In the past, astronomers have seen tantalizing hints of auroral activity on Neptune, for example, in the flyby of NASA’s Voyager 2 in 1989. However, imaging and confirming the auroras on Neptune has long evaded astronomers despite successful detections on Jupiter, Saturn, and Uranus. Neptune was the missing piece of the puzzle when it came to detecting auroras on the giant planets of our solar system.

“Turns out, actually imaging the auroral activity on Neptune was only possible with Webb’s near-infrared sensitivity,” said lead author Henrik Melin of Northumbria University, who conducted the research while at the University of Leicester. “It was so stunning to not just see the auroras, but the detail and clarity of the signature really shocked me.”

The data was obtained in June 2023 using Webb’s Near-Infrared Spectrograph. In addition to the image of the planet, astronomers obtained a spectrum to characterize the composition and measure the temperature of the planet’s upper atmosphere (the ionosphere). For the first time, they found an extremely prominent emission line signifying the presence of the trihydrogen cation (H₃⁺), which can be created in auroras. In the Webb images of Neptune, the glowing aurora appears as splotches represented in cyan.

“H₃⁺ has a been a clear signifier on all the gas giants — Jupiter, Saturn, and Uranus — of auroral activity, and we expected to see the same on Neptune as we investigated the planet over the years with the best ground-based facilities available,” explained Heidi Hammel of the Association of Universities for Research in Astronomy, Webb interdisciplinary scientist and leader of the Guaranteed Time Observation program in which the data were obtained. “Only with a machine like Webb have we finally gotten that confirmation.”

The auroral activity seen on Neptune is also noticeably different from what we are accustomed to seeing here on Earth, or even Jupiter or Saturn. Instead of being confined to the planet’s northern and southern poles, Neptune’s auroras are located at the planet’s geographic mid-latitudes — think where South America is located on Earth.

This is due to the strange nature of Neptune’s magnetic field, originally discovered by Voyager 2 in 1989, which is tilted by 47 degrees from the planet’s rotation axis. Since auroral activity is based where the magnetic fields converge into the planet’s atmosphere, Neptune’s auroras are far from its rotational poles.

The ground-breaking detection of Neptune’s auroras will help us understand how Neptune’s magnetic field interacts with particles that stream out from the Sun to the distant reaches of our solar system, a totally new window in ice giant atmospheric science.

From the Webb observations, the team also measured the temperature of the top of Neptune’s atmosphere for the first time since Voyager 2’s flyby. The results hint at why Neptune’s auroras remained hidden from astronomers for so long.

“I was astonished — Neptune’s upper atmosphere has cooled by several hundreds of degrees,” Melin said. “In fact, the temperature in 2023 was just over half of that in 1989.”

Through the years, astronomers have predicted the intensity of Neptune’s auroras based on the temperature recorded by Voyager 2. A substantially colder temperature would result in much fainter auroras. This cold temperature is likely the reason that Neptune’s auroras have remained undetected for so long. The dramatic cooling also suggests that this region of the atmosphere can change greatly even though the planet sits over 30 times farther from the Sun compared to Earth.

Equipped with these new findings, astronomers now hope to study Neptune with Webb over a full solar cycle, an 11-year period of activity driven by the Sun’s magnetic field. Results could provide insights into the origin of Neptune’s bizarre magnetic field, and even explain why it’s so tilted.

“As we look ahead and dream of future missions to Uranus and Neptune, we now know how important it will be to have instruments tuned to the wavelengths of infrared light to continue to study the auroras,” added Leigh Fletcher of Leicester University, co-author on the paper. “This observatory has finally opened the window onto this last, previously hidden ionosphere of the giant planets.”

These observations, led by Fletcher, were taken as part of Hammel’s Guaranteed Time Observation program 1249. The team’s results have been published in Nature Astronomy.

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/News

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Hannah Braun
Space Telescope Science Institute, Baltimore, Maryland

Christine Pulliam
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Science: Henrik Melin (Northumbria University)

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• Northumbria University Press Release

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A chance alignment in Lupus

NGC 5530

A spiral galaxy, seen tilted at a slight angle, on a dark background of space. It glows softly from its centre, throughout its disc out to the edge. The disc is a broad swirl of webs of dark reddish dust and sparkling blue patches where stars have formed. Atop the centre of the galaxy there is a star that appears very large and bright with four spikes emanating from it, because it is relatively close to Earth. Credit: ESA/Hubble & NASA, D. Thilker

The subject of today’s NASA/ESA Hubble Space Telescope Picture of the Week is the stunning spiral galaxy NGC 5530. NGC 5530 is situated 40 million light-years away in the constellation Lupus (The Wolf). This galaxy is classified as a ‘flocculent’ spiral, meaning that its spiral arms are patchy and indistinct.

While some galaxies have extraordinarily bright centres where they host a feasting supermassive black hole, the bright source near the centre of NGC 5530 is not an active black hole but instead a star within our own galaxy, only 10 thousand light-years from Earth. This chance alignment gives the appearance that the star is at the dense heart of NGC 5530.

If you had pointed a backyard telescope at NGC 5530 on the evening of 13 September 2007, you would have seen another bright point of light adorning the galaxy. That night, Australian amateur astronomer Robert Evans discovered a supernova, named SN 2007IT, by comparing NGC 5530’s appearance through the telescope to a reference photo of the galaxy. While it’s remarkable to discover even one supernova using this painstaking method, Evans has in fact discovered more than 40 supernovae this way! This particular discovery was truly serendipitous: it’s likely that the light from the supernova had completed its 40-million-year journey to Earth just days before the explosion was discovered.

Source: ESA/Hubble/potw

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Galaxy Clusters 4.1 Billion Years Away (Left) and 6.2 Billion Years Away (Right)

Detail: Low Res. (142 KB)  - Mid. Res. (570 KB) - High Res. (5.10 MB)

As the Universe expands, the wavelengths of light emitted from distant celestial objects are stretched, causing the light to appear redder. This phenomenon is known as redshift, where light from more distant objects becomes redder. In the case of these two galaxy clusters, the cluster located 6.2 billion light-years away (right) is farther than the cluster 4.1 billion light-years away (left), showing redder colors. Redshift is crucial for astronomers to measure a precise distance to a distant object.
Please click 4.1 Billion Years Away（ 9.2 MB ） / 6.2 billion light-years away（ 9.8 MB） for high-resolution images. Credit: NAOJ; Image provided by Masayuki Tanaka

Instrument: Hyper Suprime-Cam (HSC)

Announcement (as of March 21, 2025):

In commemorating the Subaru Telescope’s 25th anniversary, we have added new gallery images twice a month since April 2024. We hope you have enjoyed the stunning images captured by the Subaru Telescope. A new series will launch in April 2025, featuring a new image of Maunakea on the first Thursday of each month and a celestial image taken by the Subaru Telescope on the third Thursday (Japan Standard Time). Please stay tuned to the Subaru Gallery throughout Fiscal Year 2025 (April 2025 – March 2026).

Source: Subaru telescope/Press Release

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NASA's Webb Telescope Unmasks True Nature of the Cosmic Tornado

Herbig-Haro 49/50 (NIRCam and MIRI Image)
Credits/Image: NASA, ESA, CSA, STScI

Herbig-Haro 49/50 (Spitzer and Webb Images)
Credits/Image: NASA, ESA, CSA, STScI, NASA-JPL, SSC

Herbig-Haro 49/50 (NIRCam and MIRI Compass Image)
Credits/Image: NASA, ESA, CSA, STScI

Herbig-Haro 49/50 Stellar Jets (Video)

Credits/Video: NASA, ESA, CSA, Joseph DePasquale (STScI), Leah Hustak (STScI), Greg Bacon (STScI), Ralf Crawford (STScI), Danielle Kirshenblat (STScI), Christian Nieves (STScI), Alyssa Pagan (STScI), Frank Summers (STScI)

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Craving an ice cream sundae with a cherry on top? This random alignment of Herbig-Haro 49/50 — a frothy-looking outflow from a nearby protostar — with a multi-hued spiral galaxy may do the trick. This new composite image combining observations from NASA’s James Webb Space Telescope’s NIRCam (Near-Infrared Camera) and MIRI (Mid-Infrared Instrument) provides a high-resolution view to explore the exquisite details of this bubbling activity.

Herbig-Haro objects are outflows produced by jets launched from a nearby, forming star. The outflows, which can extend for light-years, plow into a denser region of material. This creates shock waves, heating the material to higher temperatures. The material then cools by emitting light at visible and infrared wavelengths.

When NASA's retired Spitzer Space Telescope observed it in 2006, scientists nicknamed Herbig-Haro 49/50 (HH 49/50) the “Cosmic Tornado” for its helical appearance, but they were uncertain about the nature of the fuzzy object at the tip of the “tornado.”  With its higher imaging resolution, Webb provides a different visual impression of HH 49/50 by revealing fine features of the shocked regions in the outflow, uncovering the fuzzy object to be a distant spiral galaxy, and displaying a sea of distant background galaxies.

HH 49/50 is located in the Chamaeleon I Cloud complex, one of the nearest active star formation regions in our Milky Way, which is creating numerous low-mass stars similar to our Sun. This cloud complex is likely similar to the environment that our Sun formed in. Past observations of this region show that the HH 49/50 outflow is moving away from us at speeds of 60-190 miles per second (100-300 kilometers per second) and is just one feature of a larger outflow.

Webb’s NIRCam and MIRI observations of HH 49/50 trace the location of glowing hydrogen molecules, carbon monoxide molecules, and energized grains of dust, represented in orange and red, as the protostellar jet slams into the region. Webb’s observations probe details on small spatial scales that will help astronomers to model the properties of the jet and understand how it is affecting the surrounding material.

The arc-shaped features in HH 49/50, similar to a water wake created by a speeding boat, point back to the source of this outflow. Based on past observations, scientists suspect that a protostar known as Cederblad 110 IRS4 is a plausible driver of the jet activity. Located roughly 1.5 light-years away from HH 49/50 (off the lower right corner of the Webb image), CED 110 IRS4 is a Class I protostar. Class I protostars are young objects (tens of thousands to a million years old) in the prime time of gaining mass. They usually have a discernable disk of material surrounding it that is still falling onto the protostar. Scientists recently used Webb’s NIRCam and MIRI observations to study this protostar and obtain an inventory of the icy composition of its environment.

These detailed Webb images of the arcs in HH 49/50 can more precisely pinpoint the direction to the jet source, but not every arc points back in the same direction. For example, there is an unusual outcrop feature (at the top right of the main outflow) which could be another chance superposition of a different outflow, related to the slow precession of the intermittent jet source. Alternatively, this feature could be a result of the main outflow breaking apart.

The galaxy that appears by happenstance at the tip of HH 49/50 is a much more distant, face-on spiral galaxy. It has a prominent central bulge represented in blue that shows the location of older stars. The bulge also shows hints of “side lobes” suggesting that this could be a barred-spiral galaxy. Reddish clumps within the spiral arms show the locations of warm dust and groups of forming stars. The galaxy even displays evacuated bubbles in these dusty regions, similar to nearby galaxies observed by Webb as part of the PHANGS program.

Webb has captured these two unassociated objects in a lucky alignment. Over thousands of years, the edge of HH 49/50 will move outwards and eventually appear to cover up the distant galaxy.

Want more? Take a closer look at the image, “fly through” it in a visualization, and compare Webb’s image to the Spitzer Space Telescope’s.

Herbig-Haro 49/50 is located about 625 light-years from Earth in the constellation Chamaeleon.

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 the Canadian Space Agency.

Source: NASA's James Webb Space Telescope/News

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Cosmic anomaly hints at frightening future for Milky Way

The giant radio jets stretching six million light-years across and an enormous supermassive black hole at the heart of spiral galaxy J23453268−0449256, as imaged by the Giant Metrewave Radio Telescope. Credit: Bagchi and Ray et al/Giant Metrewave Radio Telescope

Licence type: Attribution (CC BY 4.0)

A terrifying glimpse at one potential fate of our Milky Way galaxy has come to light thanks to the discovery of a cosmic anomaly that challenges our understanding of the universe.

An international team of astronomers led by CHRIST University, Bangalore, found that a massive spiral galaxy almost one billion light-years away from Earth harbours a supermassive black hole billions of times the Sun’s mass which is powering colossal radio jets stretching six million light-years across.

That is one of the largest known for any spiral galaxy and upends conventional wisdom of galaxy evolution, because such powerful jets are almost exclusively found in elliptical galaxies, not spirals.

It also means the Milky Way could potentially create similar energetic jets in the future – with the cosmic rays, gamma rays and X-rays they produce wreaking havoc in our solar system because of increased radiation and the potential to cause a mass extinction on Earth.

A re-think of galaxy evolution

"This discovery is more than just an oddity – it forces us to rethink how galaxies evolve, and how supermassive black holes grow in them and shape their environments," said lead author Professor Joydeep Bagchi, of CHRIST University, Bangalore.

"If a spiral galaxy can not only survive but thrive under such extreme conditions, what does this mean for the future of galaxies like our own Milky Way?

"Could our galaxy one day experience similar high-energy phenomena that will have serious consequences for the survival of precious life in it?"

In the new study, which has been published in Monthly Notices of the Royal Astronomical Society, researchers unravelled the structure and evolution of the spiral galaxy 2MASX J23453268−0449256, which is three times the size of the Milky Way.

Using observations from the Hubble Space Telescope, the Giant Metrewave Radio Telescope, the Atacama Large Millimeter Wave Array and multi-wavelength analyses, they detected an enormous supermassive black hole at its heart and radio jets that are among the largest known for any spiral galaxy, making it a rare phenomenon.

Traditionally, scientists believed that the violent activity of such colossal jets of supermassive black holes would disrupt the delicate structure of a spiral galaxy.

Yet, against all odds, 2MASX J23453268−0449256 has retained its tranquil nature with well-defined spiral arms, a luminous nuclear bar, and an undisturbed stellar ring – all while hosting one of the most extreme black holes ever observed in such a setting.

Adding to the enigma, the galaxy is surrounded by a vast halo of hot, X-ray-emitting gas, providing key insights into its history. While this halo slowly cools over time, the black hole's jets act like a cosmic furnace, preventing new star formation despite the presence of abundant star-making material.

Colour image of J23453268-0449256, which is 300,000 light-years across, as captured by the Hubble Space Telescope. It is shown alongside a depiction of our own Milky Way galaxy, which is three times smaller. Credit: Bagchi and Ray et al/Hubble Space Telescope

Licence type: Attribution (CC BY 4.0)

How this compares to Milky Way

Our own Milky Way has a 4 million solar mass black hole – Sagittarius A (Sgr A*) – at its centre, but this is currently in an extremely quiet and dormant state.

That could change if a gas cloud, star, or even a small dwarf galaxy were to be accreted (effectively eaten), the researchers said, potentially triggering significant jet activity. Such events are known as Tidal Disruption Events (TDE) and several have been observed in other galaxies, but not in the Milky Way

. If large jets like this were to emerge from Sgr A*, their impact would depend on their strength, direction, and energy output, the researchers said.

One pointed near our solar system could strip away planetary atmospheres, damage DNA and increase mutation rates because of radiation exposure, while if Earth were exposed to a direct or nearby jet, it could degrade our ozone layer and lead to a mass extinction.

A third possibility is that a powerful jet could alter the interstellar medium and affect star formation in certain regions, which is what has happened in the galaxy the new paper focused on.

Astronomers believe the Milky Way likely had large-scale radio jets in the past and although it could potentially generate them again in the future, experts aren't able to say exactly when because it depends on many factors.

Dark matter clues

The team of researchers also discovered that J23453268−0449256 contains 10 times more dark matter than the Milky Way, which is crucial for stability of its fast spinning disc.

By revealing an unprecedented balance between dark matter, black hole activity, and galactic structure, the experts said their study opens new frontiers in astrophysics and cosmology.

"Understanding these rare galaxies could provide vital clues about the unseen forces governing the universe – including the nature of dark matter, the long-term fate of galaxies, and the origin of life," said co-author Shankar Ray, a PhD student at CHRIST University, Bangalore.

"Ultimately, this study brings us one step closer to unravelling the mysteries of the cosmos, reminding us that the universe still holds surprises beyond our imagination."

Submitted by Sam Tonkin

Source: Royal Astronomical Society (RAS)/News

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Media contacts

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

Dr Robert Massey
Royal Astronomical Society
Mob: +44 (0)7802 877 699
press@ras.ac.uk

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Scientific contacts

Professor Joydeep Bagchi
CHRIST University, Bangalore
joydeep.bagchi@christuniversity.in

Suraj Dhiwar
Inter-University Centre for Astronomy and Astrophysics
suraj@iucaa.in

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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 and review 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 peer review, in which fellow experts on the editorial boards accept the paper as worth considering. 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 X,Facebook,LinkedIn YouTube.

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Gravitationally Lensed Gravitational Waves from Black Holes Around Black Holes

I

llustration of stellar-mass black holes embedded within the accretion disk of a supermassive black hole.
Credit: Caltech/R. Hurt (IPAC)

Diagram of a binary black hole system orbiting within the disk of a supermassive black hole
The observer is located at N in this diagram.
Credit:Leong et al. 2025

Gravitational-wave detectors have captured the chirps of dozens of merging black holes. Could any of these mergers have happened in the disk around a supermassive black hole?

Black Holes Around Black Holes

At the centers of galaxies across the universe, the disks surrounding accreting supermassive black holes — known as active galactic nuclei — provide an extreme ecosystem for stars and stellar-mass black holes. When a pair of black holes within an active galactic nucleus disk merges, the collision produces gravitational waves that can be picked up by detectors on Earth. If, from our perspective, that merger takes place behind the supermassive black hole, the gravitational-wave signal will be gravitationally lensed: split into two “images” of the same wave with slightly different properties.

Detecting a gravitationally lensed gravitational-wave signal from merging black holes would provide valuable information about the population of black holes that reside in active galactic nucleus disks, as well as the properties of the disks themselves.

Constraints able to be placed on the fraction of binary black hole mergers happening in active galactic nucleus disks as a function of the number of observations, Nobs, and the distance between the binary system and the central supermassive black hole, indicated by the fill pattern. The filled area shows the values that are ruled out. This plot assumes that no gravitationally lensed gravitational waves are observed. Adapted from Leong et al. 2025

Lensing Likelihood

So far, no gravitationally lensed gravitational waves have been detected — but luckily, even this non-detection contains valuable information. To explore the implications of this non-detection, Samson Leong (The Chinese University of Hong Kong) and collaborators developed an analytical model that describes a binary black hole pair orbiting and merging within the disk of an active galactic nucleus. The team calculated the probability that gravitational waves from the merger of these black holes would be gravitationally lensed from the perspective of a distant observer. This probability is dependent upon the orientation of the disk relative to the viewer, as well as the distance from the binary system to the central supermassive black hole.

Then, given the fact that none of the dozens of mergers detected so far have had gravitationally lensed signals, Leong’s team constrained the fraction of observed mergers happening in active galactic nucleus disks. With only about 100 binary black hole merger observed to date, the constraining power of the non-detection is limited. For now, all that can be said is that no more than 47% of the observed mergers took place in the disks around active galactic nuclei. As the number of detected black hole mergers grows, the constraint will grow more stringent; if no lensed events have been observed after roughly 1,000 mergers have been detected, that would mean that no more than 5% of the mergers took place within an active galactic nucleus disk.

Similar to the previous figure, but this time emphasizing the impact of the orbital distance of the merging black holes. The vertical dotted lines indicate the locations of potential migration traps. Adapted from Leong et al. 2025

To Be Constrained

This estimate is based on the assumption that all black holes in active galactic nucleus disks merge within the migration trap nearest the central supermassive black hole. Several migration traps — particular orbital radii within the disk where black holes are expected to collect — are predicted to exist. If the black holes instead merge within a migration trap at a much larger radius, many more observations will be needed to narrowly constrain the number of mergers happening within accretion disks.

Future observations may yield new information about active galactic nucleus accretion disks. In particular, it may be possible to discern the minimum size of an accretion disk, as well as where within the disk binary black holes are most likely to merge.

By Kerry Hensley

Citation

“Constraining Binary Mergers in Active Galactic Nuclei Disks Using the Nonobservation of Lensed Gravitational Waves,” Samson H. W. Leong et al 2025 ApJL 979 L27. doi:10.3847/2041-8213/ad9ead

 

Source: American Astronomical Society/AAS-Nova

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