NuSTAR Observes a Rare Supernova

An artist’s impression of a Type Ia supernova – the explosion of a white dwarf locked in a binary system with a companion star. Image credit: ESA/ATG medialab/C. Carreau.  Download Image

Over the past week, NuSTAR observed supernova SN 2026sqf, a rare type of supernova, which was discovered on July 8th by an amateur astronomer in Utah. Supernovae, or exploding stars, are empirically classified based on how their brightness and spectroscopic properties evolve over time. Some supernovae, such as Type II supernovae, occur at the end of a massive star’s life. Others, known as Type Ia supernovae, are the result of a binary star system where a white dwarf accretes from its companion and crosses over a critical mass limit that causes it to detonate completely. One very rare subclass of the latter, representing << 1% of Type Ia supernovae, have spectra that show narrow emission lines due to interactions with dense gas and dust surrounding the star. This matter is called circumstellar material (CSM) and these rare cosmic explosions are called Type Ia-CSM supernovae. Studying such events provide one of the few direct probes of mass loss from the supernova progenitor system in its late evolutionary stages. However, the high-energy view of such systems remains almost entirely unexplored. Until recently, SN 2012ca, detected by NASA's Chandra X-ray Observatory months to years after the explosion, was the only SN Ia-CSM detected in X-rays. High-energy X-rays above ~10 keV, as probed by NuSTAR, are critical to constrain the temperature of the emitting plasma and break degeneracies that are inherent to modeling X-ray spectra when only low-energy data is available. NuSTAR observations of SN 2026sqf in the nearby galaxy NGC 3310 represents, to our knowledge, the first high-energy X-ray observation of a Type Ia-CSM supernova. These data will enable unique constraints on the temperature and properties of the material surrounding this system, which, in turn, will provide clues to the properties of its progenitor.

Author: Nayana AJ, Postdoctoral Scholar (UC Berkeley)

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

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Observing in phase with binary orbits September 25th, 2026

An artist's impression of a high-mass X-ray binary, in which a compact object such as a neutron star accretes matter from a massive companion star. Image credit: ESO/L. Calçada/M.Kornmesser. Download Image

The recent NuSTAR observing schedule has been dominated by Target of Opportunity observations and coordinated observations with other high energy observatories. Among the time-constrained observations, several were scheduled to study precise moments in the orbital phases of binary systems. These include an observation of AXJ1700.2-4220, a recently rediscovered X-ray pulsator found while searching the HEASARC archive of X-ray data. Most systems discovered in this way are likely white dwarf binary systems, but the archival data for AXJ1700.2-4220 suggest the presence of an accreting neutron star in a rare binary system. With the goal of unambiguously assessing the nature of this unusual system, NuSTAR observed the source during the orbital phase when pulsations were expected to be strongest. NuSTAR has also obtained multiple observations of the gamma-ray binary system LS I +61 303 to sample key phases across its 26.5-day orbit. The NuSTAR observations were originally planned for later this year, but an independent campaign of observations with the Nordic Optical Telescope, timed to be performed around the expected peak of X-ray flaring activity, persuaded the NuSTAR Science Operations Center to bring forward those observations. The NuSTAR and multi-observatory data from these observing campaigns, which include a Director's Discretionary Time observation by ESA's XMM-Newton observatory, will be part of a collaboration between multiple teams of researchers.

Author: Karl Forster (NuSTAR Science Operations Manager, Caltech)

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

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The Heartbeat of a Windy Black Hole

An artist's impression of a black hole accreting matter from a companion star and driving powerful winds from its accretion disk. Credit: John A. Paice.  Download Image

The past few weeks of the NuSTAR program has been heavily dominated by target-of-opportunity (ToO) investigations, including observations of X-ray binaries in outburst, Galactic novae, variable stars, and magnetars. As part of this regular diet of ToOs, over the past week NuSTAR observed 4U 1630-47—a candidate black hole X-ray binary in our Galaxy—as part of a comprehensive spectroscopic campaign coordinated with the IXPE, XMM-Newton, and XRISM observatories. 4U 1630-47 is an intriguing source that exhibits variable disk wind signatures, abnormally high X-ray polarization, and multiple classes of outbursts on a quasi-annual recurrence time. NuSTAR observations are crucial for determining the temperature and distribution of the hot plasma of electrons near the black hole known as the corona, and these observations have already sampled three different states of the central engine. Meanwhile, coordinated lower-energy X-ray observations by XMM and XRISM will measure atomic transitions, allowing study of the corona's reflection off the encircling accretion disk as well as the associated wind of ionized plasma.

Of particular note, NuSTAR had its first detection of 4U 1630-47 transitioning between a high-energy-dominated “heartbeat" state and a more stable low-energy-dominated state. The NuSTAR heartbeat of 4U 1630-47 appears very different from the famed heartbeat of the Galactic black hole binary GRS 1915+105, which is generally seen at lower X-ray energies. NuSTAR's unique broadband capabilities will be essential for testing whether the two oscillation modes have the same physical origin, and the multi-facility coordinated campaign will provide insight into how matter falls into stellar mass black holes in our Galaxy, and how the energy released leads to material being ejected in a powerful wind.

Author: Maxime Parra (JSPS Postdoctoral Fellow, Ehime University, Japan)

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

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NuSTAR as a fast X-ray transient detector

This artist’s illustration shows a high-speed jet of material being launched from a gamma-ray burst source embedded in a very dusty galaxy—the sort of powerful explosion that may cause high-energy fast X-ray transients. Image credit: NOIRLab/NSF/AURA/M. Garlick. Download Image

On August 28th, NuSTAR detected a fast X-ray transient (FXT) in the field of view of an observation of a distant quasar. FXTs are flashes of X-rays that last for seconds to hours that may be related to Gamma-ray bursts and the collapse of massive stars. FXTs were first serendipitously found in Chandra observations, and the field is currently being revolutionized by the Einstein Probe. Recently, staff scientist Murray Brightman, a member of the NuSTAR Science Operations Center, implemented a program to search for these transients in NuSTAR data in near real time, soon after the data are downloaded and processed at the SOC. Since NuSTAR detects higher energy X-rays than Chandra or Einstein Probe, FXTs detected by NuSTAR may be a distinctly different type of source than FXTs detected by lower-energy instruments. Finding these sources in real time allows for follow-up with other telescopes. Murray alerted the community about the event on August 28th, named NuSTAR 260828, by submitting a GCN (https://gcn.nasa.gov/circulars/45478). Two teams followed up the event by observing with optical telescopes to search for a counterpart (https://gcn.nasa.gov/circulars/45488 and https://gcn.nasa.gov/circulars/45507). None has been found so far, but the search continues.

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

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A Supermassive Cosmic Dance

Artist's impression of a pair of supermassive black holes orbiting each other, surrounded by accreting material from a circumbinary disk. Image credit: NAOJ. Download Image

Over the past week, NuSTAR observed 4C +37.11, the only confirmed supermassive black hole binary in an active galaxy with spatially resolved orbital motion. This system was originally identified in 2004 by the Very Long Baseline Array (VLBA) as a pair of central, compact, flat-spectrum, variable radio sources with a measured separation of 7.3 pc—evidence of a pair of gravitationally bound supermassive black holes. Subsequent VLBA observations claim the detection of relative proper motion between the binary components. Numerical simulations predict that accretion in supermassive black hole binaries can generate excess hard X-ray emission above 20 keV through shocks and heated mini-disks fed by circumbinary gas streams. NuSTAR will test those predictions of a significant hard excess, or see if the X-ray spectrum follows a standard AGN power law. This test of binary accretion physics in a wide-separation supermassive black hole binary will establish whether a hard X-ray diagnostic that can be applied to unresolved binary AGN candidates identified by LSST and future time-domain surveys.

Author: Daniel Stern (NuSTAR Deputy Principal Investigator, Caltech)

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

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A Busy Month in the Galactic Center

A deep X-ray image of the Galactic center taken with the Chandra observatory, with low-, intermediate-, and high-energy X-rays colored in red, green, and blue respectively. It shows thousands of point sources, all powered by accreting white dwarfs, neutron stars, or black holes, embedded in large clouds of hot gas. Sources from this enormous population will frequently go into outburst, prompting astronomers to trigger target-of-opportunity observations to track their evolution. Image credit: NASA/CXC/UMass/D. Wang et al. Download Image

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It has been a busy month for the NuSTAR observatory. NuSTAR has in the past performed on average six Target of Opportunity (ToO) observations each month, but the numbers have been steadily increasing over the summer, in part because the Sun has moved away from the position on the sky of the Galactic center, a particularly active part of the sky. So far this month there have been 22 ToO submissions to NuSTAR, five of which were ToO proposals from the Guest Observer (GO) program, and a further five approved Director's Discretionary Time proposals—a new record for time-domain observation requests! More than half of these have been requests to observe transient sources within 5 degrees of the Galactic center, including observations for three GO programs of a bright, previously unknown transient X-ray source, MAXI J1750-327, coordinated with NASA's IXPE mission. Other ToO requests have taken advantage of the new policy allowing short NuSTAR exposures, either splitting up GO observations to increase the number of visits or performing brief monitoring visits to well-known X-ray binaries to keep track of their behavior and to alert the community when an expected outburst begins. Up until recently, the Swift mission has performed the majority of this kind of monitoring. The increase in NuSTAR time domain observations will help to cover some of this lost capability, but it will not be able to replace the key role Swift has played in the X-ray astronomy ecosystem. We salute the Swift team for their extraordinary work over the past decades and the great teamwork the Swift and NuSTAR observatories have been able to achieve together, and wish them the best in their final months of operations.

Author: Karl Forster (NuSTAR Science Operations Lead, Caltech)

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

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Hunting for the Source of Superfast Electrons with NuSTAR

A multi-wavelength image of the supernova remnant shell of PWN G0.9+0.1, combining high-energy X-ray data from NuSTAR (green), low-energy X-ray data from XMM-Newton (blue), and radio data from MeeRKAT (red). The pulsar remnant of the supernova explosion is the compact X-ray source at the center of the image, while the brighter compact X-ray source to the lower right is unrelated. The radio data shows the shape of the nebula, as well as the fainter outer shell of the supernova remnant. Image credit: Brunelli et al. (2026)/MeerKAT (Heywood et al. 2022)/H. Earnshaw. Download Image

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Earth is continuously bombarded with cosmic rays—particles such as protons and electrons flying through space incredibly fast. The faster a particle travels, the more energy it has, and a small fraction of these cosmic rays have energies greater than a petaelectronvolt, or PeV. This is about the energy of a buzzing housefly, which might not seem like a lot, but it's all contained in one single, incredibly energetic electron moving at mind-blowing, relativistic speed. Accelerating electrons to such extreme speeds takes a cosmic-scale particle accelerator, which astronomers have nicknamed a 'PeVatron'. But what kind of astronomical source could be capable of such a feat?

Pulsar wind nebulae are some of the most fascinating objects in our Galaxy. They are created in the aftermath of a supernova, the explosion of a massive star at the end of its life when it has exhausted its fuel supply. Supernovae usually leave behind a compact remnant, either a black hole or a neutron star, and a rapidly spinning neutron star can appear to pulse, almost like a light house. This inspired the term “pulsar” to describe such remnants. A rapidly spinning pulsar will illuminate the extended bubble of outflowing material from the explosion, producing highly energetic particles accelerated by the strong magnetic field of the nebula. Pulsar wind nebulae can be detected at X-ray and even gamma-ray energies, making these cosmic powerhouses ideal candidates in the hunt for PeVatrons.

Dr. Kaya Mori of Columbia University is leading a large program with NASA’s NuSTAR X-ray satellite to hunt for PeVatrons in pulsar wind nebulae in our Galaxy. NuSTAR is the first satellite to focus high-energy X-ray photons, making it the most sensitive instrument for studying the Universe at X-ray energies above 10 keV, roughly the energy of X-ray machines you'd find at a hospital. One of the nebulae studied is this program is G0.9+0.1, a young supernova remnant in the Galactic Center. In a recent paper published in the Astrophysical Journal led by PhD student Giulia Brunelli at INAF Bologna, high-energy X-ray data from NuSTAR is combined with multiwavelength data from radio and gamma-ray observatories. Modeling these observations, the team determined that this pulsar wind nebula is very young—about 2,200 years old—and capable of accelerating electrons up to 2 PeV. This makes G0.9+0.1 a compelling PeVatron candidate, meaning that it—and perhaps other pulsar wind nebulae churning away in the Galactic Center—may be one of the objects responsible for some of the highest-energy particles arriving at Earth.

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

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A Middle-Aged Supernova Remnant Stays Energetic

Combined X-ray observations of the Puppis A supernova remnant from Chandra and XMM-Newton, showing the shock waves of material expanding out into space. Low-energy X-rays are shown in red, medium-energy X-rays are in green and higher energy X-rays are colored blue. NuSTAR observations will be able to probe higher energies still. Image credit: NASA/CXC/IAFE/G.Dubner et al & ESA/XMM-Newton. Download Image

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During the past week, NuSTAR observed the supernova remnant Puppis A, the expanding debris of a stellar explosion that occurred roughly 4,000 years ago. While supernova remnants are widely believed to be the primary accelerators of Galactic cosmic rays, clear evidence for ongoing production of very high-energy particles is usually found only in much younger systems. Recent X-ray observations, however, revealed a hint of an unexpected enhancement of hard X-rays in the eastern region of Puppis A, where the blast wave is interacting with dense interstellar clouds. These observations suggest the presence of a reflected shock — a secondary shock wave generated when the expanding remnant encounters surrounding material — that may be accelerating particles even today. The primary goal of the NuSTAR observation is to determine whether the newly discovered hard X-rays are produced by freshly accelerated electrons. If confirmed, Puppis A would provide one of the clearest and most remarkable examples of active particle acceleration in middle-aged supernova remnants. Given its age of about 4,000 years, finding signs of fresh acceleration would demonstrate that supernova remnants can continue to energize particles far longer than traditionally expected, offering a rare opportunity to study how cosmic-ray factories evolve long after the original stellar explosion. By measuring the high-energy X-ray spectrum up to energies of tens of keV, NuSTAR will determine how these particles are accelerated, estimate the maximum energies they can reach, and probe the magnetic environment within the shock. These measurements will provide new insight into the long-term evolution of shock acceleration and the origin of cosmic rays in our Galaxy.

Author: Hiromasa Suzuki (Assistant Professor, University of Miyazaki, Japan)

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

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A bright X-ray flare from a tidal disruption event

An artist's i,br,brmpression of a tidal disruption event in an active galaxy, in which a star is torn up by the gravitational force from a nearby supermassive.. black hole. Image credit: NASA/CXC/M.Weiss. - Download Image

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This week's significant event is from Maya Nunez, a rising sophomore at California State University, Long Beach, who is doing a Summer Undergraduate Research Fellowship (SURF) with the NuSTAR group at Caltech. Maya is working with Murray Brightman, a NuSTAR Staff Scientist, on transient X-ray sources—that is, X-ray sources that rapidly change in brightness, such as new X-ray sources that suddenly appear in the sky. X-ray transients can be caused by a wide variety of astrophysical processes, including Tidal Disruption Events (TDEs), which occur when a star passes too close to a supermassive black hole and is torn apart. Maya identified a bright X-ray flare from a galaxy hosting an actively accreting supermassive black hole, i.e., an active galaxy. Back in 2019, this galaxy had hosted the bright optical and infrared transient AT2019fdr, whose origin has been under much debate. AT2019fdr is hypothesized to be either a superluminous supernova, a flare from a supermassive black hole, or a TDE. Maya led an approved NuSTAR Director's Discretionary Time proposal to observe this source, and the observations, obtained last week, detected the source in the 3–8 keV NuSTAR energy band. The NuSTAR data provide a late-time X-ray detection from AT2019fdr which, in combination with recent literature, solidifies AT2019fdr’s categorization as a TDE as opposed to a superluminous supernova, since late-time X-ray emission is not common for such supernovae. A flare from a supermassive black hole is also less probable, but not completely ruled out. These new data and findings will expand our understanding of TDEs, particularly TDEs in galaxies with actively accreting supermassive black holes, which have not been as well-studied as TDEs in inactive or quiescent galaxies.

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

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Could Colliding Stellar Winds Power Cosmic Rays?

This composite image shows in the RCW 38 stellar cluster in different wavelengths. In red are the X-rays from

young, hot stars and extended hot gas as imaged by Chandra, embedded in a molecular cloud (green) imaged in infrared by the ISAAC camera, and a ring of radio emission (blue) detected by ATCA from a region of gas heated by the radiation from the hot stars in the cluster. Image credit: NASA/CXC/CfA/S.Wolk et al./ISAAC/VLT/ATCA - Download Image

During the past week, NuSTAR observed RCW 38, a gigantic star-forming region full of young massive stars, each dozens of times heavier than the Sun. These stars blast out powerful winds—streams of hot, ionized gas—at speeds of up to 2000 km/s, releasing energy over their lifetimes comparable to a supernova explosion. Where many such stars are packed together, their winds collide with each other and create powerful shocks, which can accelerate atomic particles to extremely high energies—a possible source of cosmic rays. RCW 38 is especially interesting: it is compact, young (less than a million years old), and apparently free of any supernova explosions. This makes it a rare place to study the effects of stellar winds alone, without other contaminants. Past observations detected X-rays from RCW 38, but were not able to distinguish whether they came from hot gas or accelerated particles. NuSTAR's unique ability to focus high-energy X-rays will help tell the two apart, and the first NuSTAR observation of  RCW 38 may be a step toward that answer.

Author: Haruki Kuramoto (PhD Student, University of Osaka, Japan)

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

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Light-bending by extreme gravity

An artist's impression of an accretion disk of material swirling into a black hole, with a hot corona illustrated by a purple haze. The apparent warping of the disk is due to the extreme gravity of the black hole bending the light paths around it. Image credit: NASA/Caltech-IPAC/Robert Hurt - Download Image

During the past week, NuSTAR performed a 5-day long observation of the nearby active galaxy MCG-06-30-15 in coordination with JAXA/NASA/ESA’s XRISM observatory and NASA’s IXPE observatory. For nearly three decades, this source has been a premier X-ray target for studying the extreme environment around a supermassive black hole. One long-standing puzzle is the dramatic variability of direct X-ray emission from the hot corona—the compact cloud of energetic particles near the central engine—while reflected X-rays off the accretion disk vary much less. One possible explanation is relativistic light-bending by the supermassive black hole: changes in the geometry of the corona, particularly its height above the black hole, will strongly affect X-ray photon paths. MCG-06-30-15 naturally cycles through bright and faint states on timescales of only a few hours, so a 5-day observation should track this evolution in real time. NuSTAR’s unique sensitivity to high-energy X-rays allows it to track both the primary coronal emission and reflected X-rays across flux states, while XRISM's unprecedented spectral resolution simultaneously measures changes in iron emission line from the accretion disk. Together, these observations will provide one of the most direct tests yet of whether relativistic light bending drives the observed X-ray variability, while revealing how the geometry of the corona evolves as the source changes brightness. Simultaneous X-ray polarization measurements from NASA’s IXPE observatory will also provide an independent probe of the coronal geometry, offering a powerful complementary test of this picture.

Author: Indrani Pal (Postdoctoral Fellow, Clemson University)

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

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The Environment Around a Supermassive Black Hole

Artist's impression of the innermost regions around a supermassive black hole, showing an accretion disk visually distorted by gravity surrounding the event horizon, and powering an outflow of material. Image credit: CfA/M. Weiss.

Download Image

During the past week, NuSTAR observed the nearby active galactic nucleus (AGN) I Zwicky 1 in coordination with the JAXA/ESA/NASA’s XRISM and ESA’s XMM-Newton X-ray observatories. I Zwicky 1 is a unique AGN from which we can learn a lot about the fundamental physics at work as material spirals into a black hole, and the processes by which supermassive black holes grow and are able to have a profound impact on their host galaxies by AGN feedback. In this AGN, we observe X-rays reflecting off the innermost regions of the accretion disk, allowing us to probe the extreme environment just outside the event horizon of the black hole. In addition, I Zwicky 1 is seen to launch an ultrafast outflow: a wind from the inner accretion disk reaching velocities up to 30% of the speed of light. These outflows carry significant energy into their host galaxies and understanding how they are launched is an important step towards understanding AGN/host galaxy feedback. I Zwicky 1 is often seen to launch X-ray flares originating in the corona, and the outflows are seen to evolve in response to these flares. Through these observations, important new insights are expected into the structure of the accretion disk around a rapidly growing black hole, the launching mechanism of the ultrafast outflows, and the connection between these outflows and the innermost regions of the accretion disk and the corona.
Author: Dan Wilkins (Research Assistant Professor, The Ohio State University)

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

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Tracing a Neutrino Ghost to Distant “Shadow Blaster” Galaxy

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Composite of Gemini North and ALMA images of "Shadow Blaster"

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Gemini North image of the field around "Shadow Blaster"

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Gemini North and ALMA image of "Shadow Blaster"

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Gravitational lensing infographic

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ALMA image of "Shadow Blaster"

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James Clerk Maxwell Telescope

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The Submillimeter Array

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Videos


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Gravitational lensing animation


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Gravitational lensing animation (Spanish)


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Zooming into “Shadow Blaster” galaxy

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Gemini North telescope on Maunakea helps uncover strongest evidence yet that distant star-forming galaxies contribute to the production of one of the Universe’s most mysterious ghost particles

A team of astronomers has identified a remarkably bright, gravitationally-lensed, star-forming galaxy as the likely source of the high-energy neutrino event IC 210922A, detected by the IceCube Neutrino Observatory in 2021. The galaxy, nicknamed “Shadow Blaster,” is located about 11 billion light-years away, providing the most concrete observational evidence yet that populations of distant star-forming galaxies play a significant role in producing high-energy cosmic neutrinos.

Neutrinos are one of the fundamental particles of the Universe. They live a ghostly existence with no electric charge, very little mass, and extremely few interactions with matter. They are also the most abundant particles with mass in the Universe, and can be created through a variety of processes, such as the decay of heavy particles, nuclear reactions in the Sun, and the explosions of stars.

Instruments on Earth have detected high-energy neutrinos arriving from space since the 1960s, and identifying their origin has been a long-standing challenge in astronomy. While scientists have identified a small number of nearby neutrino sources [1], they cannot account for the total amount of neutrinos our instruments measure arriving from across the Universe, referred to as the cosmic neutrino background. Astronomers, therefore, suspect that other major source populations exist but remain hidden.

In a study published today in Nature Astronomy, a team led by Yuji Urata of MITOS Science Co., LTD. in Taiwan presents the analysis of a new neutrino source candidate — an extremely bright galaxy, JCMT0402−0424, nicknamed “Shadow Blaster.” This galaxy is located about 11 billion light-years away, has trillions of times the luminosity of the Sun in the infrared, and may provide the long-sought link between high-energy neutrino production and distant star-forming galaxies.

The discovery was made in part using observations from the International Gemini Observatory, partly funded by the U.S. National Science Foundation (NSF) and operated by NSF NOIRLab. The study also utilized observations from the James Clerk Maxwell Telescope (JCMT), operated by the East Asian Observatory, and the Submillimeter Array (SMA), a joint operation between the Center for Astrophysics | Harvard & Smithsonian and the Academia Sinica Institute of Astronomy and Astrophysics. All three of these telescopes are located on the summit of Maunakea in Hawai‘i.

In 2021, the NSF IceCube Neutrino Observatory in Antarctica alerted the scientific community to a high-energy neutrino event, dubbed IC 210922A, coming from a region of space in the direction of the constellation Eridanus. This alert triggered rapid follow-up observations across the electromagnetic spectrum to search for a counterpart signal that, if detected, could help identify the neutrino’s source.

Multiple teams of scientists conducted follow-up observations using a variety of telescopes and instruments. However, they all reported no convincing gamma-ray, X-ray, or optical counterpart, nor any gamma-ray burst, supernova, or tidal disruption event that could be associated with the alert [2].

Then, a couple of days after the initial alert, Urata and his team initiated observations with JCMT and SMA and discovered Shadow Blaster, whose location and brightness made it a promising candidate for the source of the signal. To investigate this galaxy further, the team organized follow-up observations with the Atacama Large Millimeter/submillimeter Array (ALMA), managed for North America by the NSF National Radio Astronomy Observatory, and they discovered that Shadow Blaster is located behind a strong gravitational lens[3].

Thanks to this lensing effect, the team would be able to study the internal structure of Shadow Blaster, which would otherwise be too distant and too faint to resolve in such detail. However, to use the lensing effect correctly and to understand how much the lens amplified the neutrino signal, they first needed to know the distance, nature, and mass distribution of the foreground galaxy. To decipher these details, they used two powerful instruments on Gemini North: the Gemini Multi-Object Spectrograph (GMOS) and the Gemini Near-InfraRed Spectrograph (GNIRS).

“The combined GMOS and GNIRS data helped us measure the distance to the lensing galaxy and determine that it is a massive elliptical galaxy. This information was crucial for estimating the lens mass distribution and constructing a model of the gravitational lens,” says Urata.

Combining the lens model with the ALMA imaging data revealed that the central region of Shadow Blaster contains an extremely compact core that is densely packed with gas and dust and forming new stars at an intense rate. Theoretical models predict that such an extreme environment can act as a natural particle accelerator, where energetic particles repeatedly collide with gas and produce neutrinos. Additionally, Shadow Blaster does not display any characteristics of possessing an active black hole. This strongly suggests that high-energy neutrinos can be produced not only by spectacular black-hole jets as scientists have observed in nearby galaxies, but also by the intense, densely packed star formation that is common in very distant galaxies.

“This breakthrough shows how particle detectors and telescopes become far more impactful when they work together, opening a powerful 'multi-messenger' window on the Universe,” says Martin Still, Program Director, NSF Office of Research Infrastructure. “By combining signals from particles and light, scientists can explore distant cosmic environments and events in unprecedented detail — revealing phenomena that were once only theoretical.”sts have observed in nearby galaxies, but also by the intense, densely packed star formation that is common in very distant galaxies.

Around 10 billion years ago, the Universe was populated with galaxies like Shadow Blaster that were actively forming stars. During this epoch, galaxies were theoretically producing large numbers of cosmic rays, which are high-energy streams of particles that can generate neutrinos. Yet obtaining observational evidence that links an individual neutrino event to such a distant galaxy has been extremely difficult since these galaxies are very far away and often deeply hidden behind thick layers of dust. Shadow Blaster's serendipitous location behind a gravitational lens makes finding this observational evidence much easier.

“Shadow Blaster possesses the kind of dense, gas-rich environment that theoretical models have long suggested could efficiently produce high-energy neutrinos,” says Urata. Combined with the absence of any more compelling counterpart despite extensive follow-up searches, Shadow Blaster is the most plausible candidate for the source of  IC 210922A. “If confirmed, Shadow Blaster would be the first-ever individual dusty star-forming galaxy directly linked to a high-energy neutrino event.”

Compact star-forming galaxies like Shadow Blaster may be numerous throughout the Universe. As a population, they may therefore contribute a significant fraction of the high-energy neutrino background that fills the cosmos. “Our analysis suggests that this population could contribute up to roughly 20% of the observed diffuse neutrino background measured by IceCube,” says Urata.

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

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Notes

[1] Astrophysical neutrino sources, or candidate source associations, that have been identified include the Sun and Supernova 1987A at lower energies, and, at high energies, the blazar TXS 0506+056, the active galaxy Messier 77, the active galaxy PKS 1424+240, and diffuse emission from the plane of the Milky Way. Candidate high-energy associations have also been reported with tidal disruption events such as AT2019dsg and AT2019fdr.

[2] Facilities used for follow-up observations: NASA's Fermi Gamma-ray Space Telescope, ANTARES neutrino telescope, NASA's Neil Gehrels Swift Observatory, Zwicky Transient Facility, High-Altitude Water Cherenkov Observatory, and the Department of Energy-funded DESI Transients Survey. In particular, DESI “spare fibers” — fibers that can’t be matched to targets from the main DESI program on a given pointing — obtained spectra for 249 galaxies within the IceCube localization region.

[3] Gravitational lensing occurs when a very massive foreground galaxy bends spacetime, acting as a cosmic magnifying glass that enlarges and distorts the image of a more distant galaxy behind it. In this case, the gravitational lens amplified the brightness of Shadow Blaster from 2.7 trillion to 33 trillion times the luminosity of the Sun in infrared light.

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More information

This research is presented in a paper titled “Compact dusty starbursts at cosmic noon linked to high-energy neutrinos,” appearing in Nature Astronomy. DOI: 10.1038/s41550-026-02884-9.

The team is composed of Y. Urata (MITOS Science Co., LTD/National Central University, Taiwan), K. Huang (Chung Yuan Christian University, Taiwan), B. Hatsukade (National Astronomical Observatory of Japan/The Graduate University for Advanced Studies/The University of Tokyo, Japan), M. Kasliwal (California Institute of Technology, USA), S. S. Kimura (Tohoku University, Japan), Y. Matsuda (National Astronomical Observatory of Japan/Ministry of Education, Culture, Sports, Science and Technology, Japan), Y. Miyamoto (Fukui University of Technology, Japan), H. Nagai (National Astronomical Observatory of Japan/The Graduate University for Advanced Studies, Japan), K. Nakanishi (National Astronomical Observatory of Japan/The Graduate University for Advanced Studies, Japan), and R. Stein (University of Maryland/NASA Goddard Space Flight Center, USA).

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 James Clerk Maxwell Telescope is operated by the East Asian Observatory, which is funded by the Academia Sinica Institute of Astronomy and Astrophysics (ASIAA, Taiwan), the National Astronomical Research Institute of Thailand (NARIT), the Science and Technology Facilities Council (STFC, United Kingdom), and other partners.

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Links

• Read the paper: Compact dusty starbursts at cosmic noon linked to high-energy neutrinos
• Press release from ALMA
• Press release from MITOS Science
• 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:

Yuji Urata
MITOS Science Co., Ltd
National Central University
Email: yjurata@gmail.com

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

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The Neutron Star That Doesn't Stop Spinning Up

A combined optical, H-alpha, and X-ray image of NGC 7793, indicating the position of the remarkably bright X-ray source P13. Image credit: NASA/CXC/ESO/VLT/NOAO/AURA/NSF/Univ of Strasbourg/M. Pakull et al. Download Image

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Last week, NuSTAR performed the first of two planned observations of the ultraluminous X-ray source NGC 7793 P13. Like its fellow ultraluminous source M82 X-2, P13 is a pulsar, meaning that its extraordinary luminosity comes from extreme levels of accretion onto a tiny neutron star, and its spin period decreases over time as the accreting material spins it up by adding angular momentum. Every now and again, P13 appears to fade dramatically in brightness but, unusually for this class of objects, when it returns to its usual luminosity again its rate of spin has increased further rather than slowing down, suggesting that it doesn't stop spinning up even when it is in a faint state. Additionally, this binary system has an orbital period a little over 60 days long, with a variation in the ultraviolet emission that is very slightly out of sync with it, which might indicate some unusual interaction between different parts of the accreting system. These NuSTAR observations will continue to track its changing period over time, helping to piece together the shape of this system and the reasons for its strange behavior.

Author: Hannah Earnshaw (NuSTAR Project Scientist, Caltech)

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

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Hunting for the Source of Superfast Electrons with NuSTAR

A multi-wavelength image of the supernova remnant shell of PWN G0.9+0.1, combining high-energy X-ray data from NuSTAR (green), low-energy X-ray data from XMM-Newton (blue), and radio data from MeeRKAT (red). The pulsar remnant of the supernova explosion is the compact X-ray source at the center of the image, while the brighter cnewsompact X-ray source to the lower right is unrelated. The radio data shows the shape of the nebula, as well as the fainter outer shell of the supernova remnant. Image credit: Brunelli et al. (2026)/MeerKAT (Heywood et al. 2022)/H. Earnshaw. Download Image

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Earth is continuously bombarded with cosmic rays—particles such as protons and electrons flying through space incredibly fast. The faster a particle travels, the more energy it has, and a small fraction of these cosmic rays have energies greater than a petaelectronvolt, or PeV. This is about the energy of a buzzing housefly, which might not seem like a lot, but it's all contained in one single, incredibly energetic electron moving at mind-blowing, relativistic speed. Accelerating electrons to such extreme speeds takes a cosmic-scale particle accelerator, which astronomers have nicknamed a 'PeVatron'. But what kind of astronomical source could be capable of such a feat?

Pulsar wind nebulae are some of the most fascinating objects in our Galaxy. They are created in the aftermath of a supernova, the explosion of a massive star at the end of its life when it has exhausted its fuel supply. Supernovae usually leave behind a compact remnant, either a black hole or a neutron star, and a rapidly spinning neutron star can appear to pulse, almost like a light house. This inspired the term “pulsar” to describe such remnants. A rapidly spinning pulsar will illuminate the extended bubble of outflowing material from the explosion, producing highly energetic particles accelerated by the strong magnetic field of the nebula. Pulsar wind nebulae can be detected at X-ray and even gamma-ray energies, making these cosmic powerhouses ideal candidates in the hunt for PeVatrons.

Dr. Kaya Mori of Columbia University is leading a large program with NASA’s NuSTAR X-ray satellite to hunt for PeVatrons in pulsar wind nebulae in our Galaxy. NuSTAR is the first satellite to focus high-energy X-ray photons, making it the most sensitive instrument for studying the Universe at X-ray energies above 10 keV, roughly the energy of X-ray machines you'd find at a hospital. One of the nebulae studied is this program is G0.9+0.1, a young supernova remnant in the Galactic Center. In a recent paper published in the Astrophysical Journal led by PhD student Giulia Brunelli at INAF Bologna, high-energy X-ray data from NuSTAR is combined with multiwavelength data from radio and gamma-ray observatories. Modeling these observations, the team determined that this pulsar wind nebula is very young—about 2,200 years old—and capable of accelerating electrons up to 2 PeV. This makes G0.9+0.1 a compelling PeVatron candidate, meaning that it—and perhaps other pulsar wind nebulae churning away in the Galactic Center—may be one of the objects responsible for some of the highest-energy particles arriving at Earth.

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

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What Powers the X-ray Emission from Distant Supermassive Black Holes?

An artist’s concept of a supermassive black hole surrounded by a swirling disk of material falling into it. The purpish ball of light above the black hole, a feature called the corona, contains highly energetic particles that generate X-ray light. Credit: NASA/JPL-Caltech/R. Hurt (IPAC). Download Image

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Supermassive black holes don't give off any light themselves, but at those times in their existence when they are actively accreting material, they are encircled by a disk of hot, glowing material. The gravity of a black hole pulls swirling gas in, heating that material and causing it to shine at energies ranging from the ultraviolet to X-rays depending on the mass of the black hole. Another major source of radiation near a black hole is the so-called “corona”. Coronae are made up of highly energetic particles that generate X-ray light, though details about their geometry, location, appearance, and how they form remain uncertain and are driving questions for X-ray astrophysicists. In the artist’s concept shown here, the corona is envisioned as a hot spot of energetic plasma above (and below) the black hole, though other models suggest the corona is a hot atmosphere to the inner accretion disk.

In a new study submitted to the Astrophysical Journal, an international team led by Dr. Xiurui Zhao of the California Institute of Technology systematically studied the X-ray coronae in some of the most distant and luminous accreting supermassive black holes ever observed. These coronae, composed of ultra-hot electrons, produce high-energy X-rays by boosting lower-energy light emitted by the accretion disk. The expansion of the universe then shifts these high-energy emitted photons to lower observed energies, similar to the Doppler shift we hear as an ambulance or police car speeds away from us and the tone of the siren shifts to lower notes. By targeting luminous accreting supermassive black holes in the distant universe, known as quasars, the team leveraged this cosmological shift to bring key spectral features into NuSTAR’s energy range. This enabled direct measurements of the coronal properties which had been out of reach of previous X-ray satellites.

By combining NuSTAR observations with observations by the European Space Agency-led XMM-Newton satellite, which is sensitive to lower energy X-rays, the team constructed the most comprehensive view to date of coronae in active galaxies across cosmic time. The results provide new constraints on how energy is dissipated and radiated near supermassive black holes, offering critical tests for state-of-the-art theoretical models and simulations.

The study reveals that coronae in these powerful, distant quasars are significantly cooler than those found in the nearby universe, where quasars are typically less luminous. This result suggests that the most luminous black holes operate in a fundamentally different physical regime. The findings also indicate that these distant coronae are denser and more efficiently cooled, likely due to intense radiation fields near rapidly accreting black holes. Together, these results challenge standard models of black hole coronae and point toward a more complex interplay between heating, cooling, and particle acceleration in these extreme environments.

In a related study to be presented at the 248^th meeting of the American Astronomical Society later this month, Dr. Zhao and collaborators report on dramatic X-ray variability detected in the corona of the galaxy Mrk 509. Mrk 509 is a relatively nearby galaxy, just shy of 500 million light years away, that hosts an actively accreting supermassive black hole. This new work, relying on observations from the NuSTAR satellite, finds very strong variations in the temperature of the corona, at a level not previously found from either Mrk 509 or similar sources. Both the distant quasar survey and this detailed study of the nearby galaxy Mrk 509 have important implications for understanding the physical processes occurring very close to supermassive black holes.

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

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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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Supermassive black hole accretion flow

An artist’s impression of a supermassive black hole, with intense radiation blasting out across the accretion disk of matter flowing into it. Image credit: NASA/JPL-Caltech. Download Image

A key question in studies of Active Galactic Nuclei (AGN) is the nature of the accretion flow around the supermassive black hole, which is still poorly understood. NGC 4051 offers a rare opportunity to observe this process around a low-mass AGN, which is also one of the brightest of its class. Its unique combination of variability, lower black hole mass, and accessibility to monitoring makes it an ideal laboratory for testing models of the innermost structure of AGN. A critical open question is the role of X-rays in irradiating the accretion disk, and how this effects the total energy observed in the system. For this purpose, NuSTAR's broad energy coverage and sensitivity are ideal for obtaining a high-quality X-ray spectrum. The NuSTAR observation performed last week completes the measurement of the broadband spectral energy distribution for NGC 4051 and is a key component to the 3-month multi-wavelength monitoring campaign of this interesting source that is currently underway.

Author: Marcin Marculewicz (Postdoctoral Fellow, Wayne State University)

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

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NuSTAR & IXPE coordinated observations of Fairall 51

An artist impression of the obscurer surrounding AGN.
Credit: R. Hurt, NASA/JPL-Caltech
Download Image

Joint observations by NuSTAR and NASA’s Imaging X-ray Polarimetry Explorer (IXPE) mission last week offer a unique window into the structure of material around the supermassive black hole at the center of the galaxy Fairall 51. The material near the black hole in this active galactic nucleus (AGN) is thought to be oriented at a peculiar angle that reveals both the black hole’s accretion disk and surrounding circum-polar dust. By combining the unique capabilities of NuSTAR and IXPE, a detailed investigation is being made of the radiation from the hot “corona” near the black hole’s accretion disk as well as X-ray photons reflected by the dust structure beyond the disk. These data will constrain how the corona is oriented relative to the putative “torus” of material around the black hole and the perpendicular polar-scattering region identified by ground-based observatories. Ultimately, this coordinated effort will reveal how the small-scale central engine is physically linked to the vast dust structures around it, providing a full picture of the environment near the accreting supermassive black hole.

Author: Chien-Ting Chen, USRA scientist & IXPE science operations at NASA/MSFC

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

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Black Hole Stars

Artists impression of a Black Hole Star. The cut-out reveals the central black hole with its surrounding accretion disk. Credit: MPIA/HdA/T. Muller/A. de Graaff. Download Image

During the past week, NuSTAR performed a 21-hour observation of J1622+3521, a newly-discovered “Green Pea” galaxy hosting a powerful accreting supermassive black hole. Green Pea galaxies were first discovered by Citizen Scientists in 2009 as bright green point-like galaxies, which we now believe are primarily compact (<5 kpc size), highly starforming (~10 solar masses per year) galaxies at a specfic distance range (average redshift ~0.25) such that the strong oxygen emission lines from the starburst are shifted into bands that produce an apparent green color. However, the oxygen emission could from processes other than star formation. Green Peas have recently gained renewed interest since the discovery of “Little Red Dots” by NASA’s James Webb Space Telescope. First identified as surprisingly bright red point-like galaxies in James Webb infrared images, scientists have been wrestling with explaining this population. One recent theory is that Little Red Dots are powered by Black Hole Stars -- enormous pristine gas stars reaching millions of solar masses powered by an accreting massive black hole at its center. One of the most powerful probes of accretion onto compact objects is X-ray observations, but so far no X-ray observatory has come close to detecting a Black Hole Star candidate. With many studies now suggesting that Green Pea galaxies could be the low-redshift analogues of Little Red Dots, the NuSTAR observations of J1622+3521 will search for conclusive evidence of a Black Hole Star from the nature of its X-ray spectrum. If J1622+3521 is powered by accretion from a spherical cloud of thick pristine gas, NuSTAR should show the strong signatures of X-ray reprocessing at energies above 10 keV, offering the most sensitive direct X-ray constraints to date on the existence of a Black Hole Star.

Author: Peter Boorman, NewAthena/WFI Project Scientist, Max Planck Institute for Extraterrestrial Physics

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

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