SPACE/COSMOS
Intergalactic experiment: Researchers hunt for mysterious dark matter particle with clever new trick
Physicists from the University of Copenhagen have begun using the gigantic magnetic fields of galaxy clusters to observe distant black holes in their search for an elusive particle that has stumped scientists for decades
University of Copenhagen
image:
Black hole galaxies emit energy and light, including gamma rays (γ) (left panel). If axions exist, some of the γ-rays would, hypothetically, turn into axions (a) as they travel through the magnetic fields surrounding clusters of galaxies. But since these magnetic fields are very intricate, it is impossible to predict such a conversion to axions in a single observation, resulting in messy data (center panel). But by combining knowledge from many of these galactic pairs, the step-like signature appears (right panel). Illustration: Lidiia Zadorozhna
view moreCredit: Illustration: Lidiia Zadorozhna
It is a story of extremes that are hard to fathom.
The heaviest structures in the universe, clusters of galaxies, are a quadrillion times more massive than the Sun. And axions, mysterious theoretical particles, are much, much lighter than even the lightest atom.
The axion is a hypothetical elementary particle that could hold the key to understanding dark matter, an unknown material that is believed to take up about 80 percent of the mass in our universe.
No one has yet proven the existence of axions, which has eluded researchers for decades. But with a clever trick involving faraway galaxies, physicists from the University of Copenhagen possibly came closer than ever before.
Instead of using a particle accelerator on Earth, like the one at CERN, the researchers turned to the cosmos and used it as a kind of gigantic particle accelerator. Specifically, they searched for electromagnetic radiation emitting from the cores of distant and very bright galaxies, each with a supermassive black hole at its center.
They then observed this radiation as it passed through the vast magnetic fields found in galaxy clusters, where some of it could hypothetically transform into axions. This transformation would leave behind tiny, random fluctuations in the data. But each signal is so faint that, on its own, it gets lost in the background noise of the universe.
So, the researchers introduced a novel concept. Instead, they observed a total of 32 supermassive black holes positioned behind galaxy clusters and then combined the data from their observations.
When the researchers examined the data, they were surprised to discover a pattern that resembled the signature of the elusive axion particle.
“Normally, the signal from such particles is unpredictable and appears as random noise. But we realized that by combining data from many different sources, we had transformed all that noise into a clear, recognizable pattern,” explains Oleg Ruchayskiy, Associate Professor at the Niels Bohr Institute of the University of Copenhagen and senior author of a new paper in Nature Astronomy that tries to study the axion. He adds:
“It shows up like a unique step-like pattern that shows what this conversion could look like. We only see it as a hint of a signal in our data, but it is still very tantalizing and exciting. You could call it a cosmic whisper, now loud enough to hear.”
Closer to discovering dark matter
While the pattern revealed by the scientists is not definite proof of the existence of axions, the research by Oleg Ruchayskiy and colleagues brings us closer to understanding what dark matter is.
“This method has greatly increased what we know about axions. It essentially enabled us to map a large area that we know does not contain the axion, which narrows down the space where it can be found,” says Postdoc Lidiia Zadorozhna, a Marie Curie fellow at the Niels Bohr Institute, who is one of the leading authors of the new paper.
While this experiment focused on a specific type of electromagnetic radiation known as gamma rays, the method can also be used on other types of radiation, like X-rays.
“We are so excited, because it is not a one-time advancement. This method allows us to go beyond previous experimental limits and has opened a new path to studying these elusive particles. The technique can be repeated by us, by other groups, across a broad range of masses and energies. That way we can add more pieces to the puzzle of explaining dark matter,” says Lidiia Zadorozhna.
Read the article “Constraints on axion-like particles from active galactic nuclei seen through galaxy clusters”.
Facts: Matter and energy in outer space
About 80 percent of the mass of the cosmos is thought to consist of dark matter. Scientists are not sure what it is, but believe that it could consist of unidentified, theoretical particles such as axions. The axion was originally proposed as a solution to an unexplained problem in the realm of particle physics known as the strong CP problem.
Galaxies are collections of stars, cosmic dust, planets, gas and dark matter often circling a supermassive black hole at the center. Galaxy clusters are groups of hundreds or thousands of galaxies bound together by gravity.
Sources: Nasa, Associate Professor Oleg Ruchayskiy
Facts: Finding the step-like pattern
Distant galaxies with a supermassive black hole at their center radiate magnitudes of energy and light. These galaxies are also powerful sources of a type of electromagnetic radiation known as gamma rays, which the researchers were interested in.
“We looked at these black holes through clusters of galaxies. Galaxy clusters are among the largest structures in the universe and reservoirs of enormous, widespread magnetic fields. They act as a sort of prism through which some of the gamma rays in theory would turn into axions,” explains Associate Professor Oleg Ruchayskiy.
By observing 32 different black holes positioned behind galaxy clusters and averaging the data from their observations, the researchers revealed the step-like signature.
Journal
Nature Astronomy
Article Title
Constraints on axion-like particles from active galactic nuclei seen through galaxy clusters
Article Publication Date
15-Aug-2025
Are they star clusters or extreme dwarf galaxies?
Astrophysicists from the Universities of Bonn and Zanjan have found evidence of an alternative formation process for this cosmic mystery
University of Bonn
Ursa Major III, the faintest object in our galaxy, orbits the Milky Way at a distance of more than 30,000 light years. Until now, it was considered a dwarf galaxy, thought to consist mainly of dark matter due to its large mass. However, an international team of astrophysicists from the University of Bonn and the Institute for Advanced Studies in Basic Sciences in Iran has found evidence suggesting that it is actually a compact star cluster containing a black hole core. The study has been published in the Astrophysical Journal Letters.
The study focuses on celestial bodies that cannot yet be clearly categorised as either star clusters or dwarf galaxies. These objects orbit the Milky Way at distances exceeding 30,000 light years. While they resemble classic star clusters outwardly, they have unusually high mass-to-light ratios; some are hundreds to thousands of times higher than those of typical dwarf galaxies. This peculiarity has led to the assumption that they contain large amounts of dark matter. “Neither established dark matter models nor alternative theories have been able to satisfactorily explain the exact causes. Such intermediate objects are therefore considered a “hot topic” in astrophysics and are the subject of intensive research,” says doctoral student and first author Ali Rostami-Shirazi from the Iranian Institute for Advanced Studies in Basic Sciences.
Focus on Ursa Major III: New evidence of a dark star cluster
Ursa Major III is the faintest known satellite of the Milky Way. These small companion galaxies orbit the Milky Way and provide important clues about its formation and composition. Previously considered a dark dwarf galaxy – a small galaxy whose mass is thought to consist mainly of dark matter – Ursa Major III has now been found to be a dark star cluster: Simulations by the research team now suggest that Ursa Major III could be a compact star cluster whose gravity is held together by a core of black holes and neutron stars rather than dark matter. “Dark star clusters form when gravitational interactions with the Milky Way over billions of years remove the outer stars from a star cluster,” explains Prof. Dr. Hosein Haghi, who is conducting research at the University of Bonn and is affiliated with the Iranian Institute for Advanced Studies in Basic Sciences in Zanjan. What remains is a dark, massive core that does not emit any light. According to the study, this effect has previously been mistakenly interpreted as evidence of dark matter.
Testing the simulations
To test the hypothesis, the research team simulated the evolution of Ursa Major III over cosmic timescales. Using specialised N-body simulations, which calculate the gravitational interactions of thousands of stars with great precision, the team reconstructed the development of Ursa Major III's current structure over time. These simulations are based on the latest observational data, including Ursa Major III's orbital motion and chemical composition.
The research team's calculations show that the observed state of Ursa Major III can be explained by a dense core of black holes holding the remaining stars together gravitationally, without the need for dark matter. “Our work shows for the first time that these objects are most likely normal star clusters,” says Prof. Dr. Pavel Kroupa, who is a member of the Transdisciplinary Research Areas (TRA) “Modelling” and “Matter” at the University of Bonn. He continues: “These results solve a major mystery in astrophysics.” Such problems can be solved effectively with the right approach to computer simulations, causing seemingly 'exotic components' in astrophysics to disappear.
The Bonn team considers itself a leader in this field. Over many years, they have developed specialised numerical methods to map the highly complex dynamics of such star systems in detail. Kroupa says, ‘Our current results provide a new basis for understanding mysterious celestial objects, while also opening up new perspectives for galaxy research.’
Funding and participating institutions
In addition to the University of Bonn, the study involved the Institute for Advanced Studies in Basic Sciences (IASBS) in Zanjan, Iran, and Charles University in Prague, Czech Republic. The Iran National Science Foundation funded the study.
Journal
The Astrophysical Journal Letters
Article Title
Dark Star Clusters or Ultra-Faint Dwarf galaxies? Revisiting UMa3/U1
Article Publication Date
7-Aug-2025
Space mice babies
Stem cells cryopreserved in space have produced healthy offspring
image:
Stem cells from mice cryopreserved on the International Space Station for six months have produced healthy offspring
view moreCredit: KyotoU / Shinohara lab
Kyoto, Japan -- As space programs evolve and we continue to mistreat our own planet, human dreams of space tourism and planetary colonization seem increasingly common. However, features of spaceflight such as gravitational changes and circadian rhythm disruption -- not to mention radiation -- take a toll on the body, including muscle wasting and decreased bone density. These may even affect our ability to produce healthy offspring.
Studying the impact of spaceflight on germ cells -- egg and sperm precursor cells -- is particularly important because they directly influence the next generation, and any irreversible damage done to these will likely be transmitted to offspring. Previous examinations of embryonic stem cells that have undergone spaceflight have revealed abnormalities, but the exact cause of the damage has remained unknown.
This inspired a team of researchers at Kyoto University to test the potential damage to spermatogonial stem cells during spaceflight and the resulting offspring. The team utilized stem cells from mice, which have a much shorter reproductive life span than humans.
The research team first cryopreserved the stem cells and then sent them to the International Space Station, where they were stored in a deep freezer for six months. The cells were then returned to Kyoto, where the team observed no apparent abnormalities. After thawing and in vitro expansion, the research team transplanted the cells into mouse testes.
Within three to four months, offspring from these frozen cells were born through natural mating. When examining the newborn mice, the research team observed that they were healthy and exhibited normal gene expression. These results suggest that cryopreserved germ cells maintain fertility for at least six months.
"It is important to examine how long we can store germ cells in the ISS to better understand the limits of storage for future human spaceflight," says first author Mito Kanatsu-Shinohara.
Stem cells from many species can be cryopreserved and still produce sperm, so these findings contribute to the laying of a foundation for the development of germ cell preservation during future long-haul space missions.
The research team originally predicted that spaceflight would be more harmful to spermatogonial stem cells than cryopreservation, due to their sensitivity to radiation. However, the results actually revealed the opposite: while the concentration of hydrogen peroxide used in cryopreservation was sufficient to kill off some of the cells, the research team observed minimal differences between the pre- and post-spaceflight germ cells.
Additional assessments are nonetheless required. The mice offspring appear normal and do not exhibit abnormal DNA patterns, but long-term health issues cannot be ruled out until the lifespan and fertility of these mice and subsequent generations of mice are properly analyzed.
"We still have some spermatogonial stem cells frozen on the ISS, so we will continue to conduct further analysis," says Kanatsu-Shinohara.
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The paper "Germline transmission of cryopreserved mouse spermatogonial stem cells maintained on the International Space Station" appeared on 15 August 2025 in Stem Cell Reports, with doi: ___
About Kyoto University
Kyoto University is one of Japan and Asia's premier research institutions, founded in 1897 and responsible for producing numerous Nobel laureates and winners of other prestigious international prizes. A broad curriculum across the arts and sciences at undergraduate and graduate levels complements several research centers, facilities, and offices around Japan and the world. For more information, please see: http://www.kyoto-u.ac.jp/en
Journal
Stem Cell Reports
Method of Research
Experimental study
Subject of Research
Animals
Article Title
Germline transmission of cryopreserved mouse spermatogonial stem cells maintained on the International Space Station
Article Publication Date
15-Aug-2025
Students’ image tool offers sharper signs, earlier detection in the lab or from space
UBC Okanagan research tech gets the most from medical and environmental imaging
University of British Columbia Okanagan campus
A group of UBC Okanagan students has helped create technology that could improve how doctors and scientists detect everything from tumours to wildfires.
Working under the guidance of Associate Professor Xiaoping Shi from UBCO’s Department of Computer Science, Mathematics, Physics and Statistics, the students designed and tested a system called an adaptive multiple change point energy-based model segmentation (MEBS).
This method uses advanced mathematics to pick out important details in complex or noisy images, the kind that often confuse existing detection methods.
“This project gave us a chance to work on something that can make a real difference,” says Jiatao Zhong, a UBCO master’s student and lead author of the study. “It’s exciting to know that what we built could help doctors spot illnesses sooner and help scientists track wildfires more effectively.”
The work, recently published in Scientific Reports, shows that MEBS can help health professionals find signs of disease in medical scans, assist plant scientists in tracking cell growth and give wildfire monitors a faster way to identify hotspots from space.
“Our students played a big role in building and refining this model, and they had a chance to apply it to real-world problems,” says Dr. Shi. “The skills they gained in programming, data analysis and applied mathematics will give them an edge in their future careers.”
The team’s research showed success across several key areas:
- In medical scans by detecting tumours and fluid buildup in X-rays and mammograms with greater clarity than standard tools.
- In wildfire monitoring by picking out small but critical sparks in satellite images, which can lead to faster response times.
- In biological research by helping scientists count and track cells in plant studies, important for agriculture and growth research.
Dr. Yuejiao Fu collaborated with Dr. Shi on the paper while the student team—Zhong, Shiyin Du, Canruo Shen, Yiting Chen, Medha Naidu and Min Gao—worked on tasks ranging from coding and testing to running experiments on medical and satellite images.
Together, they demonstrated that MEBS can do what many existing tools cannot: automatically adapt when an image does not follow typical patterns, improving accuracy without extra manual work.
Most image tools use fixed rules that don’t always work in the real world. Medical scans and satellite images are often noisy or inconsistent.
MEBS stands out because it adapts to the image itself—detecting subtle shifts and dividing complex visuals into useful sections. This leads to more accurate results for doctors, scientists and wildfire monitors alike.
The project was supported by the Natural Sciences and Engineering Research Council of Canada and UBC Okanagan’s Office of the Vice-Principal, Research and Innovation.
Method of Research
Meta-analysis
Subject of Research
Not applicable
Article Title
Energy-based segmentation methods for images with non-Gaussian noise
As the atmosphere changes, so will its response to geomagnetic storms
Satellite operators can expect less density during space weather events
Rising concentrations of carbon dioxide in the upper atmosphere will change the way geomagnetic storms impact Earth, with potential implications for thousands of orbiting satellites, according to new research led by scientists at the US. National Science Foundation National Center for Atmospheric Research (NSF NCAR).
Geomagnetic storms, caused by massive eruptions of charged particles from the surface of the Sun that buffet Earth’s atmosphere, are a growing challenge for our technologically dependent society. The storms temporarily increase the density of the upper atmosphere and therefore the drag on satellites, which impacts their speed, altitude, and how long they remain operational.
The new study used an advanced computer model to determine that the upper atmosphere’s density will be lower during a future geomagnetic storm compared with a present-day storm of the same intensity. That’s because the baseline density will be lower, and future storms won’t increase it to levels as high as what occurs with storms currently.
However, the relative magnitude of the density increase — the rise from baseline to peak during a multiday storm — will be greater with future storms.
“The way that energy from the Sun affects the atmosphere will change in the future because the background density of the atmosphere is different and that creates a different response,” said NSF NCAR scientist Nicolas Pedatella, the lead author. “For the satellite industry, this is an especially important question because of the need to design satellites for specific atmospheric conditions.”
The study, a collaboration with Japan’s Kyushu University, was published in Geophysical Research Letters.
Colder and thinner air
Earth’s upper atmosphere has become increasingly important in recent decades because of society’s dependence on advanced navigation systems, online data transmission, national security applications, and other technologies that rely on satellite operations.
Unlike the lower atmosphere, which warms with emissions of carbon dioxide, the upper atmosphere becomes colder. This has to do with the varying impacts of carbon dioxide: instead of absorbing and reemitting heat to nearby molecules in the relatively dense air near Earth’s surface, carbon dioxide reemits the heat out into space at high altitudes where the air is much thinner.
Previous studies have estimated the extent to which increasing levels of carbon dioxide and other greenhouse gases will lead to a decrease in the upper atmosphere’s neutral density, or its concentration of non-ionized particles such as oxygen and nitrogen. But Pedatella and his colleagues posed a somewhat different question: how will future atmospheric density change during powerful geomagnetic storms?
The researchers homed in on the geomagnetic superstorm of May 10-11, 2024, when a series of powerful solar disturbances known as coronal mass ejections buffeted Earth’s atmosphere. They analyzed how the atmosphere would have responded to the same storm in 2016 and in three future years that will each occur around the minimum of the 11-year solar cycle (2040, 2061, and 2084).
To perform the analysis, they turned to an NSF NCAR-based modeling system, the Community Earth System Model Whole Atmosphere Community Climate Model with thermosphere-ionosphere eXtension, that simulates the entire atmosphere from Earth’s surface to the upper thermosphere, 500-700 kilometers (about 310-435 miles) above the surface. This enables scientists to determine how changes in the lower atmosphere, such as higher concentrations of greenhouse gases, can affect remote regions of the atmosphere far aloft.
They ran the simulations on the Derecho supercomputer at the NSF NCAR-Wyoming Supercomputing Center.
The researchers found that, later this century, various regions of the upper atmosphere will be 20-50% less dense at the peak of a storm comparable to the one that occurred last year, assuming significantly higher carbon dioxide levels. However, compared with the atmosphere’s density just before and after the storm, the relative change in density will be greater. Whereas such a storm now more than doubles the density at its peak, it may nearly triple it in the future. This is because the same storm will have a proportionately larger impact on a less dense atmosphere.
Pedatella said more research is needed to better understand how space weather will change, including studying different types of geomagnetic storms and whether their impacts will vary at various times in the 11-year solar cycle, when the atmosphere’s density changes.
“We now have the capability with our models to explore the very complex interconnections between the lower and upper atmosphere,” he said. “It’s critical to know how these changes will occur because they have profound ramifications for our atmosphere.”
About the article
Title: Impact of Increasing Greenhouse Gases on the Ionosphere and Thermosphere Response to a May 2024-Like Geomagnetic Superstorm
Authors: Nicholas M. Pedatella, Huixin Liu, Han-Li Liu, Adam Herrington, Joseph McInerney
Journal: Geophysical Research Letters
This material is based upon work supported by the NSF National Center for Atmospheric Research, a major facility sponsored by the U.S. National Science Foundation and managed by the University Corporation for Atmospheric Research. Any opinions, findings and conclusions or recommendations expressed in this material do not necessarily reflect the views of NSF.
Journal
Geophysical Research Letters
Article Title
Impact of Increasing Greenhouse Gases on the Ionosphere and Thermosphere Response to a May 2024-Like Geomagnetic Superstorm
Rotation-corrected satellite precise orbit determination method boosts navigation precision for future mega-constellations
Aerospace Information Research Institute, Chinese Academy of Sciences
Precise orbit determination (POD) is vital for satellite navigation, positioning, and timing services, especially as large Low Earth Orbit (LEO) constellations grow in scale. A new method integrates inter-satellite link (ISL) data with onboard BeiDou-3 (BDS-3) observations to simultaneously determine the orbits of both LEO and BDS-3 Medium Earth Orbit (MEO) satellites. The technique addresses the problem of systematic constellation rotation by referencing the coordinate system implied in BDS-3 broadcast ephemerides and applying a rotation correction. Simulations show that this approach reduces LEO orbit errors from over 20 cm to about 1 cm, offering low-latency, high-accuracy solutions without heavy reliance on ground tracking stations.
Modern satellite constellations such as OneWeb, Starlink, and CENTISPACETM promise global communications and navigation capabilities using LEO constellations. However, their POD requires dense ground station networks—costly and often limited by geopolitical or geographical constraints. Inter-satellite links (ISLs) help reduce ground dependence but suffer from "rotational unobservability", where the entire constellation drifts in orientation due to the lack of an absolute spatial reference. Existing fixes often require additional infrastructure or high-quality Global Navigation Satellite System (GNSS) products, which increase latency and operational complexity. Due to these challenges, a more autonomous, low-latency approach that leverages existing onboard capabilities is needed to ensure reliable, high-accuracy orbits for mega-constellations.
Wuhan University researchers have developed and validated a rotation-corrected integrated POD method that fuses ISL measurements with onboard BeiDou-3 (BDS-3) GNSS observations. Published (DOI: 10.1186/s43020-025-00175-8) in Satellite Navigation on August 4, 2025, the study demonstrates how the technique simultaneously estimates the orbits of Low Earth Orbit (LEO) and BDS-3 Medium Earth Orbit (MEO) satellites, corrects systematic rotation using BDS-3 broadcast ephemerides, and achieves centimeter-level precision. The approach significantly reduces reliance on ground stations, making it well-suited for real-time applications in large-scale LEO constellations.
The team simulated a 66-satellite LEO constellation equipped with ISLs and onboard BDS-3 receivers, alongside 24 real BDS-3 MEO satellites. Two processing strategies were tested: one using BDS-3 data from all LEOs, and another from only a subset. In both cases, ISL and GNSS data were jointly processed to form a unified high–low constellation. Due to internal-only measurements, the initial solutions exhibited significant systematic rotation—up to 40 cm cross-track error for LEOs and over 1 m for MEOs. The researchers derived rotation angles between the integrated POD coordinate frame and the BeiDou Coordinate System implied in broadcast ephemerides, then applied a Helmert transformation to correct the orbits. After correction, LEO along-track and cross-track errors dropped from 22.7 cm and 39.3 cm to 1.3 cm and 4.2 cm, respectively. MEO errors fell from over 1.2 m to about 13 cm. Even when only 36 of 66 LEOs carried GNSS receivers, ISL connectivity propagated the correction across the constellation with minimal accuracy loss. Tests also examined the influence of predicted Earth Rotation Parameters and residual errors in broadcast ephemerides.
"This method tackles one of the most stubborn issues in autonomous constellation orbit determination—systematic rotation caused by the lack of absolute spatial reference," said Dr. Kecai Jiang, corresponding author of the study. "By harnessing readily available BDS-3 broadcast ephemerides and inter-satellite measurements, we can deliver centimeter-level precision without waiting for post-processed GNSS products or building extensive ground networks. This approach is not only efficient but also scalable, paving the way for real-time, high-accuracy navigation services in future mega-constellations."
The rotation-corrected integrated POD method holds significant promise for global navigation augmentation, autonomous LEO-based navigation systems, and real-time positioning services. By dramatically reducing reliance on ground infrastructure, it enables resilient operations in remote or geopolitically constrained regions. Its scalability makes it ideal for next-generation satellite constellations supporting broadband internet, disaster response, and precision agriculture. Moreover, the ability to achieve near-uniform accuracy across all satellites—even when only part of the constellation carries GNSS receivers—lowers hardware requirements and operational costs. This innovation could become a cornerstone technology for integrating LEO constellations with existing GNSS systems to enhance global navigation and timing performance.
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References
DOI
Original Source URL
https://doi.org/10.1186/s43020-025-00175-8
Funding information
This study is financially supported by the National Natural Science Foundation of China (Grant Nos. 42204020, 42030109), and the China Postdoctoral Science Foundation (Grant Nos. 2021M702507).
About Satellite Navigation
Satellite Navigation (E-ISSN: 2662-1363; ISSN: 2662-9291) is the official journal of Aerospace Information Research Institute, Chinese Academy of Sciences. The journal 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
Integrated precise orbit determination for LEO constellation and BDS-3 MEO satellites using inter-satellite links and onboard BDS-3 observations
Article Publication Date
14-Aug-2025
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