SPACE/COSMOS
Dark matter in the center of the Milky Way not ruled out
A new machine-learning method incorporates the energy of photons for the first time
University of Vienna
An international research collaboration between the University of Vienna and Lawrence Berkeley National Laboratory in the United States has used machine learning to re-examine one of the most hotly debated signals in astrophysics. The so-called Galactic Center Excess (GCE), a faint, roughly spherical glow of gamma rays at the center of the Milky Way, has fascinated physicists for more than a decade. The new results suggest that an explanation in terms of dark matter cannot currently be ruled out. The results have now been published in the journal Physical Review Letters.
The Galactic Center Excess (GCE) is a roughly spherical glow of gamma rays extending over thousands of light years around the center of the Milky Way. Several explanations have been proposed for this unusual signal: theoretical predictions are consistent with self-annihilating dark matter. Another possibility is a large population of rapidly rotating neutron stars known as millisecond pulsars. The origin of the signal at the center of our galaxy therefore remains unresolved.
“Interpreting the signal is particularly difficult because the Galactic Center is an exceptionally bright and crowded region of the gamma-ray sky,” explains Florian List, study author and researcher at the University of Vienna.
Including Photon Energies for the First Time Brings a Decisive Change
The pulsar hypothesis has been supported by previous statistical studies. However, earlier analyses did not include a crucial piece of information: the energy of each individual detected photon. In the new study, the research group developed a machine-learning method trained on more than a million simulated gamma-ray observations. The aim was to evaluate spatial and spectral information simultaneously for the first time.
Including this energy information changes the picture substantially. Whereas earlier analyses pointed to comparatively bright, unresolved light sources (point sources), the new results show that these point sources would have to be extremely faint. “Our new analysis shows that the sources would have to be so faint that they would be almost indistinguishable from the emission expected from annihilating dark matter”, says Nick Rodd, study author and scientist at the Lawrence Berkeley National Laboratory.
For the pulsar hypothesis, this would imply that there must be at least 35,000 such sources in the center of the Milky Way — significantly more than the few hundred to few thousand sources assumed in some previous studies.
Dark matter remains plausible in the debate about the center of the Milky Way
“The origin of the Galactic Center Excess is one of the longest-running debates in astrophysics,” says Florian List. “Our work does not show that dark matter is responsible for the signal. However, it suggests that it is still too early to rule out this possibility.”
The new results weaken one of the strongest arguments so far against the dark-matter hypothesis. Although the study does not provide direct evidence for dark matter, the hypothesis that the Galactic Center Excess is due to dark matter remains a plausible explanation in the debate.
Summary:
- The Galactic Center Excess (GCE) is a roughly spherical glow of gamma rays at the center of the Milky Way.
- One possible origin of this glow is a population of rapidly rotating neutron stars, known as millisecond pulsars. The new results show that dark matter also remains a plausible explanation.
- In the new study, the research group developed a machine-learning method that incorporated photon energies for the first time.
- The study does not show that dark matter is responsible for the signal. However, it suggests that it is still too early to rule out this possibility.
About the University of Vienna:
At the University of Vienna, curiosity has been the core principle of academic life for more than 650 years. For over 650 years the University of Vienna has stood for education, research and innovation. Today, it is ranked among the top 100 and thus the top four per cent of all universities worldwide and is globally connected. With degree programmes covering over 180 disciplines, and more than 10,000 employees we are one of the largest academic institutions in Europe. Here, people from a broad spectrum of disciplines come together to carry out research at the highest level and develop solutions for current and future challenges. Its students and graduates develop reflected and sustainable solutions to complex challenges using innovative spirit and curiosity.
Journal
Physical Review Letters
Article Title
Energy Distribution of the Galactic Center Excess’s Sources
Article Publication Date
17-Jun-2026
Third time’s the charm for a row of faint galaxies without dark matter
Astronomers have followed a faint, cosmic trail of gas to a third galaxy that has no dark matter.
In a new study in The Astrophysical Journal, a team of Yale astronomers reports on a dwarf galaxy located45 million light-years from Earth — called NGC 1052-DF9 — that appears to have formed in a straight line with nine other galaxies.
Two of those other galaxies, DF2 and DF4, were previously shown to lack dark matter — an invisible, theorized material that gives shape to the universe and is thought by most astronomers to be essential to galaxy formation.
Now, DF9 has joined the no-dark-matter club.
“A line of galaxies lacking dark matter has never been seen before,” said Michael Keim, a Ph.D. student in astrophysics in Yale’s Graduate School of Arts and Sciences and first author of the new study. “The discoveryprovides some of the strongest evidence yet that these galaxies formed through an extreme and previously unseen process and offers a rare new window into the nature of dark matter itself.”
Keim’s advisor, Yale astronomer Pieter van Dokkum, led the original studies that analyzed DF2 and DF4, using data from the Hubble Space Telescope. Van Dokkum, the Sol Goldman Family Professor of Astronomy and professor of physics in Yale’s Faculty of Arts and Sciences, is co-author of the new study.
During his doctoral work with van Dokkum, Keim found DF9 — which had been misidentified as a supermassive black hole — and proposed a thorough analysis with W.M. Keck Observatory’s Cosmic Web Imager, in Hawaii, which is designed specifically to study faint starlight such as the light emitted by DF9.
The researchers measured the motions of stars within DF9 to determine its mass. They found that DF9 has the mass of 100 million suns — which is consistent with the expected amount of visible matter in a galaxy of its size — and nothing else. If DF9 also had the expected amount of dark matter, its mass would be equal tomore than 10 billion suns.
DF9’s lack of dark matter strongly suggests that DF2, DF4, and DF9 formed together in the same violent event, such as a high-speed collision between galaxies, Keim said. In this scenario, the collision would have separated out gas from the galaxies’ dark matter — and that gas went on to form new galaxies in a linear trail.
“Up until now it was assumed galaxies formed within pools of dark matter called ‘halos,’” Keim said. “This system shows that stars and galaxies can form outside of dark matter ‘halos’ in extreme events and indicates that dark matter is a physical substance that can act independently of normal matter or gas, challenging alternative theories that dark matter is gravity.”
In this regard, the new study reaffirms van Dokkum’s original work on DF2 and DF4, which also suggested that dark matter is a separate material.
The researchers are now conducting follow-up observations with other telescopes — including the new Mothra telescope co-founded by van Dokkum and University of Toronto astronomer Roberto Abraham — to search for any gas that was left behind after the initial galaxy collision.
Co-authors of the study are former Yale Ph.D. student Zili Shen, Yale postdoctoral researcher Imad Pasha, and Princeton astronomer Shany Danieli.
Article Title
A Third Galaxy Missing Dark Matter along a Trail of Galaxies in the NGC 1052 Field
Article Publication Date
16-Jun-2026
Analysis of supernova data questions evidence for cosmic acceleration
Research led by the Tata Institute of Fundamental Research, Mumbai along with Professor Subir Sarkar from the University of Oxford questions the widely accepted argument that the expansion rate of the universe is accelerating and that this is driven by ‘dark energy’ arising from the quantum vacuum. Their letter has been published in Monthly Notices of the Royal Astronomical Society. The findings divide opinion; in the same journal issue, a paper co-authored by Professor Maria Vincenzi also from the University of Oxford maintains that evidence does indeed point to the universe still accelerating.
In his work, Professor Subir Sarkar of Oxford's Rudolf Peierls Centre for Theoretical Physics, together with Animesh Sah and Mohamed Rameez of the Tata Institute of Fundamental Research in India, revisited one of cosmology's most important observational datasets: the Pantheon+ compilation of more than 1,700 Type Ia supernovae. For more than 25 years, astronomers have used observations of these supernovae – exploding stars – to measure the expansion of the universe. Analysis of such observations led to the groundbreaking discovery that cosmic expansion appears to be accelerating – a finding that won the 2011 Nobel Prize in Physics.
The team analysed the supernovae from the Pantheon+ dataset, one of the most comprehensive catalogues of its kind, and incorporated a recently proposed correction that takes into account the age of the stars that eventually produce these supernova explosions. They also checked whether the inferred acceleration of the expansion rate is indeed the same in every direction, as is assumed in the standard cosmological model.
‘There is increasing evidence that the brightness of Type Ia supernovae depends on the age of the stars they come from,’ said Professor Subir Sarkar of Oxford's Rudolf Peierls Centre for Theoretical Physics, a co-author of the study. ‘If this effect is not accounted for, it can lead to the erroneous conclusion that the expansion rate is accelerating.’
After applying the correction, the researchers found that the data no longer support a picture of a uniformly accelerating Universe. Instead, their analysis suggests that cosmic expansion is overall slowing down rather than speeding up.
Professor Sarkar and his colleagues came to their conclusion by considering whether the inferred acceleration may in fact be anisotropic, meaning it exhibits different properties when measured in different directions and therefore deviates from the standard cosmological model. If that were true, they argue that dark energy couldn’t be responsible for driving the acceleration because an effect of the quantum vacuum cannot be anisotropic.
‘We found that the inferred acceleration is directed mainly along the direction that we are moving locally, as indicated by the hotspot in the cosmic microwave background, and dies away with distance,’ explains Professor Sarkar. ‘This is unaffected by the correction to the supernova brightness – so rejects dark energy independently of whether the correction is applied or not. The correction turns the isotropic component into a deceleration – which again rules out dark energy.’
This paper’s findings go against the widely accepted viewpoint that the universe is still accelerating – a discovery that was awarded the Nobel Prize in 2011. In the same journal issue, a paper co-authored by Professor Maria Vincenzi also from the University of Oxford maintains that evidence does indeed point to the universe still accelerating and she comments: ‘The lead authors of our study are world experts in understanding how the environments of Type Ia supernovae affect cosmological measurements with more than a decade of experience in both supernova astrophysics and galaxy evolution. Our recent findings provide further confidence in the cosmological framework that has emerged over the past three decades and allow the research community to focus on one of the biggest unanswered questions in physics: the nature of dark energy itself.’
Looking ahead, both schools of thought will be able to test their findings and explore further using data from the Rubin Observatory’s Legacy Survey of Space and Time (LSST), which will soon measure hundreds of thousands of supernovae.
Paper references:
Pantheon+ supernovae corrected for progenitor age indicate the universe is decelerating, A Sah, M. Rameez & S. Sarkar, Monthly Notices of the Royal Astronomical Society, 11 June 2026 https://doi.org/10.1093/mnras/stag844
Still accelerating: type Ia supernova cosmology is robust to host galaxy age evolution, P Wiseman et al, Monthly Notices of the Royal Astronomical Society, 10 June 2026 https://doi.org/10.1093/mnras/stag797
For media enquiries, contact Professor Subir Sarkar: subir.sarkar@physics.ox.ac.uk
About the University of Oxford
Oxford University has been placed number 1 in the Times Higher Education World University Rankings for the tenth year running, and number 3 in the QS World Rankings 2024. At the heart of this success are the twin-pillars of our ground-breaking research and innovation and our distinctive educational offer.
Oxford is world-famous for research and teaching excellence and home to some of the most talented people from across the globe. Our work helps the lives of millions, solving real-world problems through a huge network of partnerships and collaborations. The breadth and interdisciplinary nature of our research alongside our personalised approach to teaching sparks imaginative and inventive insights and solutions.
Through its research commercialisation arm, Oxford University Innovation, Oxford is the highest university patent filer in the UK and is ranked first in the UK for university spinouts, having created more than 300 new companies since 1988. Over a third of these companies have been created in the past five years. The university is a catalyst for prosperity in Oxfordshire and the United Kingdom, contributing around £16.9 billion to the UK economy in 2021/22, and supports more than 90,400 full time jobs.
Journal
Monthly Notices of the Royal Astronomical Society
Article Title
Pantheon + supernovae corrected for progenitor age indicate the universe is decelerating
Solar wind forecasting will help define heliosphere’s boundaries
New study predicts when the SwRI-led New Horizons mission will exit the solar system
image:
To understand and define the boundaries of our heliosphere, SwRI researchers collaborated with other scientists to use existing numerical simulations to reveal the structure of the heliosphere and its interaction with the interstellar medium. Solar wind data and solar wind pressure forecasts provide important information for heliospheric models to help predict when the New Horizons spacecraft will encounter the heliospheric termination shock, on its way to joining the Voyager 1 and 2 spacecraft in interstellar space.
view moreCredit: NASA/IBEX/Adler Planetarium/SwRI
SAN ANTONIO — June 22, 2026 —Southwest Research Institute (SwRI) scientists are using a solar wind forecasting method combined with analytic and numerical heliosphere models to find out where the first plasma boundary of the outer heliosphere lies as NASA’s New Horizons spacecraft hurtles toward this mysterious region of space.
The heliosphere, a vast bubble of plasma created by the solar wind flowing outward from the Sun, surrounds the entire solar system and shields it from much of the high-energy galactic radiation found in interstellar space. Scientists believe the heliosphere resembles a comet because the Sun moves through the interstellar medium, creating a rounded “nose” region and a trailing “tail.” Other models predict a croissant-shaped heliosphere.
SwRI researchers are studying the heliosphere’s dynamic outer boundaries, including the termination shock and the heliopause, where the solar wind slows and then abruptly stops when interacting with interstellar material. These boundaries constantly expand and contract in response to changing solar conditions. During solar maximum, the “turbocharged” solar wind expands the heliosphere. During solar minimum, the ebbing solar wind allows the heliosphere to contract.
Two recent scientific papers are exploring how to accurately predict the location of the termination shock, particularly in the direction New Horizons is traveling.
After completing historic flybys of Pluto and Kuiper Belt object Arrokoth, New Horizons continues deeper into the outer solar system on a trajectory toward the heliosphere’s forward region. It will reach the termination shock and later leave the solar system, only the third spacecraft to do so after Voyager 1 and 2. Scientists hope to determine when the spacecraft will encounter this plasma boundary surrounding the solar system.
“We want to understand when the spacecraft will reach the termination shock to prepare to take measurements and download data about this region,” said Dr. Jonathan Gasser, lead author of the two papers. “Based on our research, we predict that New Horizons will encounter the termination shock as early as 2029 or as late as 2040. And it is possible that it could cross the boundary more than once as the heliosphere continues to expand and contract.”
The research could improve our understanding of how the heliosphere interacts with interstellar space and help future missions explore the boundaries between the solar system and the interstellar space beyond.
To read the Astrophysical Journal paper titled “Solar Wind Forecasting for Long-term Variations of the Global Heliosphere,” go to https://doi.org/10.3847/1538-4357/ae3152.
To read the Advances in Space Research paper titled “Predictions of New Horizons’ Termination Shock Crossing,” go to https://doi.org/10.1016/j.asr.2026.04.074.
For more information, visit https://www.swri.org/markets/earth-space/space-research-technology/space-science/heliophysics.
Journal
Advances in Space Research
Method of Research
Data/statistical analysis
Subject of Research
Not applicable
Article Title
Predictions of New Horizons’ Termination Shock Crossing
Article Publication Date
15-Jun-2026
New positioning framework cuts satellite navigation convergence time from minutes to seconds
image:
Schematic of the A-GBPS-augmented GNSS positioning system: GNSS satellites (black) and A-GBPS base stations (gold) broadcast positioning signals; the CBM station (gray) receives these signals and forwards carrier-phase observations to the user (blue). The base stations operate without time synchronization.
view moreCredit: Satellite Navigation
As demand grows for high-precision navigation in autonomous vehicles, mobile mapping, robotics, and other real-time applications, one challenge continues to limit performance: the long time required for satellite positioning systems to reach full accuracy. A new study proposes a solution by combining satellite navigation with signals from asynchronous ground-based transmitters that do not require costly time synchronization. The researchers developed a tightly coupled positioning framework that fuses information from both sources, enabling faster convergence and improved positioning accuracy. The findings suggest that existing terrestrial communication infrastructure could be repurposed to enhance next-generation navigation services with low deployment complexity and cost.
Precise Point Positioning (PPP), a high-accuracy Global Navigation Satellite System (GNSS) technique, offers the advantage of centimeter-level positioning without relying on local reference stations. However, PPP often requires many minutes—and sometimes longer—to achieve full precision, making it less suitable for dynamic environments. Previous efforts have shown that Ground-Based Positioning Systems (GBPS) can accelerate convergence by providing additional geometric constraints. Yet most GBPS solutions depend on highly accurate time synchronization among base stations, which increases infrastructure costs and limits deployment flexibility. Asynchronous Ground-Based Positioning Systems (A-GBPS) remove this synchronization burden, but their potential for augmenting PPP has remained largely unexplored. Deeper investigation into practical PPP augmentation with A-GBPS is needed.
Researchers from the Department of Electronic Engineering at Tsinghua University report a new GNSS augmentation framework in a study published (DOI: 10.1186/s43020-026-00200-4) in 2026 in the journal Satellite Navigation. The researchers developed a tightly coupled positioning architecture that integrates GNSS with A-GBPS. By combining satellite and A-GBPS observations, the framework significantly accelerates positioning convergence and improves solution stability, offering a practical pathway toward more efficient high-precision navigation services.
Rather than requiring all base stations to share the same clock, the new framework embraces their asynchronous nature. The researchers developed a method that uses a dedicated monitoring station to correct transmitter clock biases before integrating the measurements with GNSS observations. This allows the system to exploit the strong signal power and favorable geometry of ground-based transmitters without the operational burden of network-wide synchronization.
The team first established a theoretical model showing that adding A-GBPS observations should reduce positioning uncertainty. Numerical simulations then demonstrated that adding A-GBPS can significantly strengthen geometric constraints, particularly in the directions where satellite-only positioning is weak. The benefits became even more pronounced after the positioning solution stabilized, suggesting that A-GBPS can complement GNSS throughout the positioning process.
To test the approach under real-world conditions, the researchers deployed six A-GBPS base stations and conducted field experiments using a mobile receiver platform. Compared with GNSS-only positioning, the augmented system reached higheraccuracy with faster convergence and delivered more stable positioning performance. The experiments also revealed an important engineering insight: adding more base stations generally improved performance, but the gains began to level off beyond about five or six stations. This finding may help future network designers balance positioning performance against deployment costs.
The authors said the work demonstrates that high-precision PPP augmentation does not necessarily require tightly synchronized GBPS. Instead, asynchronous GBPS can provide valuable geometric information that improves both convergence speed and positioning reliability. They said the results indicate that existing terrestrial communication facilities, like 5G, could potentially support future positioning services. Such an approach may offer a practical pathway toward more accessible high-precision navigation without high deployment expense and complexity, which usually associated with synchronized GBPS.
The implications extend beyond navigation research. Faster and more reliable positioning could benefit autonomous driving systems, unmanned aerial vehicles, intelligent transportation networks, surveying operations, and mobile mapping platforms that depend on rapid access to precise location information. Because the framework is compatible with existing radio infrastructure, it may lower barriers to deployment and expand positioning coverage in challenging environments. The researchers note that future work will focus on eliminating the need for a dedicated monitoring station and evaluating performance under more complex urban conditions, where signal blockage and multipath interference are more prominent.
###
References
DOI
Original Source URL
https://doi.org/10.1186/s43020-026-00200-4
About Satellite Navigation
Satellite Navigation (ISSN: 2662-1363; ISSN: 2662-9291) Satellite Navigation is the official journal of the Aerospace Information Research Institute. The aims to report innovative ideas, new results or progress on the theoretical techniques and applications of satellite navigation. The journal welcomes original articles, reviews and commentaries.
Journal
Satellite Navigation
Subject of Research
Not applicable
Article Title
A GNSS PPP framework augmented using asynchronous ground-based positioning systems
Article Publication Date
12-Jun-2026
Tracing a neutrino ghost to distant “shadow blaster” galaxy
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
Association of Universities for Research in Astronomy (AURA)
image:
Left: the field around the gravitationally lensed galaxy nicknamed “Shadow Blaster.” This galaxy lies 11 billion light-years away and sits just behind the bright red galaxy at the center of this image.
Center: a close-up of the gravitational lens in which the red foreground galaxy is causing the light from the more distant Shadow Blaster galaxy to bend around it, creating multiple distorted images of the galaxy that appear as yellow arcs.
Right: a close-up of the gravitationally lensed Shadow Blaster galaxy.
These images were captured with the Atacama Large Millimeter/submillimeter Array (ALMA) and the Gemini North telescope, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation and operated by NSF NOIRLab.
view moreCredit: International Gemini Observatory/NOIRLab/NSF/AURA/ALMA (ESO/NAOJ/NRAO) Image Processing: T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), D. de Martin & M. Zamani (NSF NOIRLab) Acknowledgment: PI: Yuji Urata (MITOS Science Co., LTD.)
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 Gemini North telescope, one half of 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.”
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.
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.
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.
Links
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Journal
Nature Astronomy
Article Title
Compact dusty starbursts at cosmic noon linked to high-energy neutrinos
Article Publication Date
17-Jun-2026
This image shows the field around the gravitationally lensed galaxy nicknamed "Shadow Blaster." This galaxy lies 11 billion light-years away and sits just behind the bright red galaxy at the center of this image. The red foreground galaxy acts like a cosmic magnifying glass, enlarging and distorting the image of the more distant Shadow Blaster galaxy behind it.
This image was captured by the Gemini North telescope, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation and operated by NSF NOIRLab.
Credit
International Gemini Observatory/NOIRLab/NSF/AURA/ Image Processing: T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), D. de Martin & M. Zamani (NSF NOIRLab) Acknowledgment: PI: Yuji Urata (MITOS Science Co., LTD.)
This image shows the gravitationally lensed galaxy nicknamed "Shadow Blaster," which astronomers have identified as the likely source of the high-energy neutrino event IC 210922A, detected by the IceCube Neutrino Observatory in 2021.Gravitational lensing occurs when a very massive foreground galaxy bends space-time,
acting as a cosmic magnifying glass that enlarges and distorts the image of a more distant galaxy behind it. In this case, the red foreground galaxy is bending the light of the more distant Shadow Blaster galaxy, creating multiple distorted images of it that appear here as yellow arcs.
This composite image was created using data from the Atacama Large Millimeter/submillimeter Array (ALMA) and the Gemini North telescope, one half of the International Gemini Observatory, partly funded by the U.S. National Science Foundation and operated by NSF NOIRLab.
Credit
International Gemini Observatory/NOIRLab/NSF/AURA/ALMA (ESO/NAOJ/NRAO) Image Processing: T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), D. de Martin & M. Zamani (NSF NOIRLab) Acknowledgment: PI: Yuji Urata (MITOS Science Co., LTD.)
This image shows a close-up of the gravitationally lensed galaxy nicknamed "Shadow Blaster," which astronomers have identified as the likely source of the high-energy neutrino event IC 210922A, detected by the IceCube Neutrino Observatory in 2021.
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, a foreground galaxy, which is not visible in this image, is bending the light of the more distant Shadow Blaster galaxy, creating multiple distorted images of it that appear here as yellow arcs.
Credit
NOIRLab/NSF/AURA/ALMA (ESO/NAOJ/NRAO) Image Processing: T.A. Rector (University of Alaska Anchorage/NSF NOIRLab), D. de Martin & M. Zamani (NSF NOIRLab)
The James Clerk Maxwell Telescope located near the summit of Maunakea in Hawai‘i.
Credit
William Montgomerie, EAO/JCMT
The Submillimeter Array at the summit of Maunakea in Hawaiʻi.
Credit
NOIRLab/NSF/AURA/L.L. Christensen
