SPACE/COSMOS
New high-definition pictures of the baby universe
The ACT collaboration has rigorously tested the standard model of cosmology and shown it to be remarkably robust. The new, polarized images of the early universe reveal the formation of ancient clouds that consolidated into the first galaxies and stars
Princeton University
image:
Research by the Atacama Cosmology Telescope collaboration has led to the clearest and most precise images yet of the universe’s infancy, the cosmic microwave background radiation that was visible only 380,000 years after the Big Bang.
This new sky map has put the standard model of cosmology through a rigorous new set of tests and show it to be remarkably robust. The new images of the early universe, which show both the intensity and polarization of the earliest light with unprecedented clarity, reveal the formation of ancient, consolidating clouds of hydrogen and helium that later developed into the first galaxies and stars.
This piece of the new sky map that shows the vibration directions (or polarization) of the radiation. The zoom-in on the right is 10 degrees high. Polarized light vibrates in a particular direction; blue shows where the surrounding light’s vibration directions are angled towards it, like spokes on a bicycle; orange shows places where the vibration directions circle around it. This new information reveals the motion of the ancient gases in the universe when it was less than half a million years old, pulled by the force of gravity in the first step towards forming galaxies. The red band comes from our closer-by Milky Way.
view moreCredit: ACT Collaboration; ESA/Planck Collaboration
New research by the Atacama Cosmology Telescope (ACT) collaboration has produced the clearest images yet of the universe’s infancy – the earliest cosmic time yet accessible to humans. Measuring light that traveled for more than 13 billion years to reach a telescope high in the Chilean Andes, the new images reveal the universe when it was about 380,000 years old – the equivalent of hours-old baby pictures of a now middle-aged cosmos.
“We are seeing the first steps towards making the earliest stars and galaxies,” says Suzanne Staggs, director of ACT and Henry deWolf Smyth Professor of Physics at Princeton University. “And we’re not just seeing light and dark, we’re seeing the polarization of light in high resolution. That is a defining factor distinguishing ACT from Planck and other, earlier telescopes.”
The new pictures of this background radiation, known as the cosmic microwave background (CMB), add higher definition to those observed more than a decade ago by the Planck space-based telescope. “ACT has five times the resolution of Planck, and greater sensitivity,” says Sigurd Naess, a researcher at the University of Oslo and a lead author of one of several papers related to the project. “This means the faint polarization signal is now directly visible.”
The polarization image reveals the detailed movement of the hydrogen and helium gas in the cosmic infancy. “Before, we got to see where things were, and now we also see how they're moving,” says Staggs. “Like using tides to infer the presence of the moon, the movement tracked by the light’s polarization tells us how strong the pull of gravity was in different parts of space.”
The new results confirm a simple model of the universe and have ruled out a majority of competing alternatives, says the research team. The work has not yet gone through peer review, but the researchers will present their results at the American Physical Society annual conference on March 19.
Measuring the universe’s infancy
In the first several hundred thousand years after the Big Bang, the primordial plasma that filled the universe was so hot that light couldn’t propagate freely, making the universe effectively opaque. The CMB represents the first stage in the universe's history that we can see – effectively, the universe’s baby picture.
The new images give a remarkably clear view of very, very subtle variations in the density and velocity of the gases that filled the young universe. “There are other contemporary telescopes measuring the polarization with low noise, but none of them cover as much of the sky as ACT does,” says Naess. What look like hazy clouds in the light’s intensity are more and less dense regions in a sea of hydrogen and helium – hills and valleys that extend millions of light years across. Over the following millions to billions of years, gravity pulled the denser regions of gas inwards to build stars and galaxies.
These detailed images of the newborn universe are helping scientists to answer longstanding questions about the universe’s origins. “By looking back to that time when things were much simpler, we can piece together the story of how our universe evolved to the rich and complex place we find ourselves in today, ” says Jo Dunkley, the Joseph Henry Professor of Physics and Astrophysical Sciences at Princeton University and the ACT analysis leader.
“We’ve measured more precisely that the observable universe extends almost 50 billion light years in all directions from us, and contains as much mass as 1,900 ‘zetta-suns’, or almost 2 trillion trillion Suns,” says Erminia Calabrese, professor of astrophysics at the University of Cardiff and a lead author on one of the new papers. Of those 1,900 zetta-suns, the mass of normal matter – the kind we can see and measure – makes up only 100. Another 500 zetta-Suns of mass are mysterious dark matter, and the equivalent of 1,300 are the dominating vacuum energy (also called dark energy) of empty space.
Tiny neutrino particles make up at most four zetta-suns of mass. Of the normal matter, three-quarters of the mass is hydrogen, and a quarter helium. “Almost all of the helium in the universe was produced in the first three minutes of cosmic time,” says Thibaut Louis, CNRS researcher at IJCLab, University Paris-Saclay and one of the lead authors of the new papers. “Our new measurements of its abundance agree very well with theoretical models and with observations in galaxies.” The elements that we humans are made of – mostly carbon, with oxygen and nitrogen and iron and even traces of gold – were formed later in stars and are just a sprinkling on top of this cosmic stew.
ACT’s new measurements have also refined estimates for the age of the universe and how fast it is growing today. The infall of matter in the early universe sent out sound waves through space, like ripples spreading out in circles on a pond.
“A younger universe would have had to expand more quickly to reach its current size, and the images we measure would appear to be reaching us from closer by”, explains Mark Devlin, the Reese W. Flower Professor of Astronomy at the University of Pennsylvania, and ACT’s deputy director. “The apparent extent of ripples in the images would be larger in that case, in the same way that a ruler held closer to your face appears larger than one held at arm’s length.” The new data confirm that the age of the universe is 13.8 billion years, with an uncertainty of only 0.1%.
The Hubble tension
In recent years, cosmologists have disagreed about the Hubble constant, the rate at which space is expanding today. Measurements derived from the CMB have consistently shown an expansion rate of 67 to 68 kilometers per second per Megaparsec, while measurements derived from the movement of nearby galaxies indicate a Hubble constant as high as 73 to 74 km/s/Mpc. Using their newly released data, the ACT team has measured the Hubble constant with increased precision. Their measurement matches previous CMB-derived estimates. “We took this entirely new measurement of the sky, giving us an independent check of the cosmological model, and our results show that it holds up,” says Adriaan Duivenvoorden, a research fellow at the Max Planck Institute for Astrophysics and lead author of one of the new papers.
A major goal of the work was to investigate alternative models for the universe that would explain the disagreement. “We wanted to see if we could find a cosmological model that matched our data and also predicted a faster expansion rate,” says Colin Hill, an assistant professor at Columbia University and one of the lead authors of the new papers. Alternates include changing the way neutrinos and the invisible dark matter behave, adding a period of accelerated expansion in the early universe or changing fundamental constants of nature.
“We have used the CMB as a detector for new particles or fields in the early universe, exploring previously uncharted terrain,” says Hill. ‘The ACT data show no evidence of such new signals. With our new results, the standard model of cosmology has passed an extraordinarily precise test.”
“It was slightly surprising to us that we didn't find even partial evidence to support the higher value,” says Staggs. “There were a few areas where we thought we might see evidence for explanations of the tension, and they just weren’t there in the data.”
A 5-year exposure
The background radiation measured by ACT is extremely faint. “To make this new measurement, we needed a 5-year exposure with a sensitive telescope tuned to see millimeter-wavelength light,” says Devlin. “Our colleagues at the National Institute of Standards and Technology provided detectors with cutting-edge sensitivity, and the National Science Foundation supported ACT’s mission for more than two decades to get us here.”
In surveying the sky, ACT has also seen light emitted from other objects in space. “We can see right back through cosmic history,” says Dunkley, “from our own Milky Way, out past distant galaxies hosting vast black holes, and huge galaxy clusters, all the way to that time of infancy.”
ACT completed its observations in 2022, and attention is now turning to the new, more capable, Simons Observatory at the same location in Chile. The new ACT data are shared publicly on NASA’s LAMBDA archive.
Research by the Atacama Cosmology Telescope collaboration has led to the clearest and most precise images yet of the universe’s infancy, the cosmic microwave background radiation that was visible only 380,000 years after the Big Bang.
This new sky map has put the standard model of cosmology through a rigorous new set of tests and show it to be remarkably robust. The new images of the early universe, which show both the intensity and polarization of the earliest light with unprecedented clarity, reveal the formation of ancient, consolidating clouds of hydrogen and helium that later developed into the first galaxies and stars.
A new image of the cosmic microwave background radiation, adding high definition from the Atacama Cosmology Telescope to an earlier image from the Planck satellite. The zoom-in is 10 degrees across, or twenty times the Moon’s width seen from Earth, and shows a tiny portion of the new half-sky image. Orange and blue show more or less intense radiation, revealing features in the density of the universe when it was less than half a million years old - a time before any galaxies had formed. The image includes closer-by objects: the red band on the right is the Milky Way, and the red dots are galaxies containing vast black holes, the blue dots are huge galaxy clusters, and the spiral Sculptor Galaxy is visible towards the bottom.
Credit
ACT Collaboration; ESA/Planck Collaboration
Research by the Atacama Cosmology Telescope collaboration has led to the clearest and most precise images yet of the universe’s infancy, the cosmic microwave background radiation that was visible only 380,000 years after the Big Bang.
This new sky map has put the standard model of cosmology through a rigorous new set of tests and show it to be remarkably robust. The new images of the early universe, which show both the intensity and polarization of the earliest light with unprecedented clarity, reveal the formation of ancient, consolidating clouds of hydrogen and helium that later developed into the first galaxies and stars.
Credit
Debra Kellner
The pre-peer review articles highlighted in this release are available on https://act.princeton.edu/ and will appear on the open-access arXiv.org. They have been submitted to the Journal of Cosmology and Astroparticle Physics. In addition to the authors mentioned, lead authors include Zachary Atkins (Princeton University), Yilun Guan (University of Toronto), Hidde Jense (CardiffUniversity), Adrien La Posta (University of Oxford), Matthew Hasselfield (Flatiron Institute) & Yuhan Wang (Cornell University).
This research was supported by the U.S. National Science Foundation (AST-0408698, AST-0965625 and AST-1440226 for the ACT project, as well as awards PHY-0355328, PHY-0855887 and PHY-1214379), Princeton University, the University of Pennsylvania, and a Canada Foundation for Innovation award. The project is led by Princeton University and the University of Pennsylvania, with 160 collaborators at 65 institutions. ACT operated in Chile from 2007-2022 under an agreement with the University of Chile, in the Atacama Astronomical Park.
Meteorites: A geologic map of the asteroid belt
Knowing from what debris field in the asteroid belt our meteorites originate is important for planetary defense efforts against Near Earth Asteroids.
image:
Geologic map of the asteroid belt. Circles identify the asteroid families from which our meteorites originate and letters mark the corresponding meteorite type. The horizontal axis ranges from short orbits moving just inside the asteroid belt (left) to longer orbits just outside (right). The vertical axis shows how much the asteroid orbits are tilted relative to the plane of the planets. Blue lines are the delivery resonances.
view moreCredit: From: Jenniskens & Devillepoix (2025) Meteoritics & Planetary Science.
March 18, 2025, Mountain View, CA -- Where do meteorites of different type come from? In a review paper in the journal Meteoritics & Planetary Science, published online this week, astronomers trace the impact orbit of observed meteorite falls to several previously unidentified source regions in the asteroid belt.
“This has been a decade-long detective story, with each recorded meteorite fall providing a new clue,” said meteor astronomer and lead author Peter Jenniskens of the SETI Institute and NASA Ames Research Center. “We now have the first outlines of a geologic map of the asteroid belt.”
Ten years ago, Jenniskens teamed up with astronomer Hadrien Devillepoix of Curtin University and colleagues in Australia to build a network of all-sky cameras in California and Nevada that can capture and track the bright light of meteorites as they hit the Earth’s atmosphere. Many institutes and citizen scientists participated in this effort over the years.
“Others built similar networks spread around the globe, which together form the Global Fireball Observatory,” said Devillepoix. “Over the years, we have tracked the path of 17 recovered meteorite falls.”
Many more fireballs were tracked by doorbell and dashcam video cameras from citizen scientists around the globe and by other dedicated networks.
“Altogether, this quest has yielded 75 laboratory-classified meteorites with an impact orbit tracked by video and photographic cameras,” said Jenniskens. “That proves to be enough to start seeing some patterns in the direction from which the meteorites approach Earth.”
Most meteorites originate from the asteroid belt, a region between Mars and Jupiter where over a million asteroids larger than 1 kilometer circle the Sun. Those rocks originate from a small number of larger asteroids that broke in collisions, the debris fields of which litter the region. Even today, asteroids collide to create debris fields within these asteroid families, called clusters.
“We now see that 12 of the iron-rich ordinary chondrite meteorites (H chondrites) originated from a debris field called “Koronis,” which is located low in the pristine main belt,” said Jenniskens. “These meteorites arrived from low-inclined orbits with orbital periods consistent with this debris field.”
Astronomers can measure how long ago these rocks were dug up from below the asteroid’s surface by measuring the level of radioactive elements created by exposure to cosmic rays. This cosmic-ray exposure age of the meteorites proves to match the dynamical age of some of the asteroid debris fields. Scientists determine the dynamical age of debris fields by measuring how much asteroids of different size have spread over time.
“By measuring the cosmic ray exposure age of meteorites, we can determine that three of these twelve meteorites originated from the Karin cluster in Koronis, which has a dynamical age of 5.8 million years, and two came from the Koronis2 cluster, with a dynamical age of 10-15 million years,” said Jenniskens. “One other meteorite may well measure the age of the Koronis3 cluster: about 83 million years.”
Jenniskens and Devillepoix also found a group of H-chondrites on steep orbits that appear to originate from the Nele asteroid family in the central main belt, which has a dynamical age of about 6 million years. The nearby 3:1 mean-motion resonance with Jupiter can pump up the inclinations to those observed. A third group of H chondrites that have an exposure age of about 35 million years originated from the inner main belt.
“In our opinion, these H chondrites originated from the Massalia asteroid family low in the inner main belt because that family has a cluster of about that same dynamical age,” said Jenniskens. “The asteroid that created that cluster, asteroid (20) Massalia, is an H chondrite type parent body.”
Jenniskens and Devillepoix find that low iron (L chondrite) and very low iron (LL chondrite) meteorites come to us primarily from the inner main belt. Scientists have long linked the LL chondrites to the Flora asteroid family on the inner side of the asteroid belt, and they have confirmed that connection.
“We propose that the L chondrites originated from the Hertha asteroid family, located just above the Massalia family,” said Jenniskens. “Asteroid Hertha doesn’t look anything like its debris. Hertha is covered by dark rocks that were shock-blackened, indicative of an unusually violent collision. The L chondrites experienced a very violent origin 468 million years ago when these meteorites showered Earth in such numbers that they can be found in the geologic record.”
Knowing from what debris field in the asteroid belt our meteorites originate is important for planetary defense efforts against Near Earth Asteroids. An approaching asteroid’s orbit can provide clues to its origin in the asteroid belt in the same way as meteorite orbits.
“Near Earth Asteroids do not arrive on the same orbits as meteorites, because it takes longer for these to evolve to Earth.” said Jenniskens. “But they do come from some of the same asteroid families.”
Jenniskens and Devillepoix discuss the links of several other meteorite types to their source regions. Not all assignments are certain.
“We are proud about how far we have come, but there is a long way to go,” said Jenniskens, “Like the first cartographers who traced the outline of Australia, our map reveals a continent of discoveries still ahead when more meteorite falls are recorded.”
What’s coming next? Asteroids directly meet meteorites when observed in space before impacting Earth and then recovered. Jenniskens guided the recovery of the first such small asteroid in 2008, called asteroid 2008 TC3, and we are about to see a lot more thanks to new astronomical facilities coming online.
Link to the paper:
https://onlinelibrary.wiley.com/doi/full/10.1111/maps.14321
About the SETI Institute
Founded in 1984, the SETI Institute is a non-profit, multi-disciplinary research and education organization whose mission is to lead humanity’s quest to understand the origins and prevalence of life and intelligence in the universe and share that knowledge with the world. Our research encompasses the physical and biological sciences and leverages data analytics, machine learning, and advanced signal detection technologies. The SETI Institute is a distinguished research partner for industry, academia, and government agencies, including NASA and the National Science Foundation.
Article Title
Review of asteroid, meteor, and meteorite-type links
Article Publication Date
17-Mar-2025
Nanomaterials used to measure first nuclear reaction on radioactive nuclei produced in neutron star collisions
Physicists have measured a nuclear reaction that can occur in neutron star collisions, providing direct experimental data for a process that had previously only been theorised. The study, led by the University of Surrey, provides new insight into how the universe’s heaviest elements are forged – and could even drive advancements in nuclear reactor physics.
Working in collaboration with the University of York, the University of Seville, and TRIUMF, Canada’s national particle accelerator centre, the breakthrough marks the first-ever measurement of a weak r-process reaction cross-section using a radioactive ion beam, in this case studying the 94Sr(α,n)97Zr reaction. This is where a radioactive form of strontium (strontium-94) absorbs an alpha particle (a helium nucleus), then emits a neutron and transforms into zirconium-97.
The study has been published as an Editors Suggestion in Physical Review Letters.
Dr Matthew Williams, lead author of the study from the University of Surrey, said:
“The weak r-process plays a crucial role in the formation of heavy elements, which astronomers have observed in ancient stars – celestial fossils that carry the chemical fingerprints of perhaps only one prior cataclysmic event, like a supernovae or neutron star merger. Until now, our understanding of how these elements form has relied on theoretical predictions, but this experiment provides the first real-world data to test those models that involve radioactive nuclei.”
The experiment was enabled by the use of novel helium targets. Since helium is a noble gas, meaning it is neither reactive nor solid, researchers at the University of Seville developed an innovative nano-material target, embedding helium inside ultra-thin silicon films to form billions of microscopic helium bubbles, each only a few 10s of nanometres across.
Using TRIUMF’s advanced radioactive ion beam technology, the team accelerated short-lived strontium-94 isotopes into these targets, allowing them to measure the nuclear reaction under conditions similar to those found in extreme cosmic environments.
Dr Williams said:
"This is a major achievement for astrophysics and nuclear physics, and the first-time nanomaterials have been used in this way, opening exciting new possibilities for nuclear research.
“Beyond astrophysics, understanding how radioactive nuclei behave is crucial for improving nuclear reactor design. These types of nuclei are constantly produced in nuclear reactors, but until recently, studying their reactions has been extremely difficult. Reactor physics depends on this kind of data to predict how often components need replacing, how long they’ll last and how to design more efficient, modern systems.”
The next phase of research will apply the findings to astrophysical models, helping scientists to better understand the origins of the heaviest known elements. As researchers continue to explore these processes, their work could deepen our understanding of both the extreme physics of neutron star collisions and practical applications in nuclear technology.
[ENDS]
Notes to editors
Dr Matthew Williams is available for interview; please contact mediarelations@surrey.ac.uk
The full paper is available at https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.134.112701
Journal
Physical Review Letters
Article Title
First Measurement of a Weak 𝑟-Process Reaction on a Radioactive Nucleus
Article Publication Date
17-Mar-2025
Euclid opens data treasure trove, offers glimpse of deep fields
Germany’s role in unveiling the dark universe
Max Planck Institute for Astronomy
Covering a vast sky area in three mosaics, the data release also includes numerous galaxy clusters, active galactic nuclei and transient phenomena. This first survey data unlocks a treasure trove of information for scientists to dive into and tackle some of the most intriguing questions in modern science. Euclid enables us to explore our cosmic history and the invisible forces shaping our universe.
With its exceptionally large field of view for a space telescope, capturing an area 240 times larger in a single shot than the Hubble Telescope, Euclid delivers outstanding image quality in both the visible and infrared light spectrum.
Crucial contributions from Germany
Euclid is particularly impressive in the infrared channel, for which the Max Planck Institute for Extraterrestrial Physics (MPE) in Garching near Munich and the Max Planck Institute for Astronomy (MPIA) in Heidelberg provided critical components. After passing through four lenses, a filter, and a beam splitter, it achieves an extraordinarily high contrast. “The requirements for suppressing ghost images are exceeded by a factor of one hundred. The optical design and the precise execution of the optics at MPE and MPIA set new standards for image sharpness and contrast,” says Frank Grupp, who led the development of the near-infrared optics at MPE.
MPE is also contributing to research on galaxy evolution. “We have compiled a catalogue of over 70,000 spectroscopic redshifts from various sky surveys and combined it with the Euclid data,” explains Christoph Saulder, who led this part of the project. “This catalogue allows for precise distance measurements and the clear identification of numerous galaxies and quasars in Euclid’s high-resolution images. It serves as a foundation for a deeper understanding of these objects, their distribution, and their internal properties.”
“The new data are also being used to test the techniques for measuring cosmic shear and calibrating redshifts, which will soon be applied to the much larger Euclid data sets to achieve the primary scientific goal – the precision measurement of dark energy,” says Hendrik Hildebrandt from Ruhr University Bochum. He leads the key project for measuring cosmic shear and the redshift calibration task force.
Furthermore, scientists at Ludwig Maximilian University (LMU) in Munich have tested methods to identify and characterize galaxy overdensities, a crucial step in tracing the universe's large-scale structure. “The methodologies used to pinpoint galaxy clusters in this task will be key to fully exploiting Euclid’s vast dataset, improving cluster identification and contributing to a deeper understanding of cosmic structure formation. At the same time, they help explore previously uncharted regimes in the near-infrared with a statistically significant sample of objects,” says LMU scientist Barbara Sartoris.
Likewise, MPIA scientists play leading roles in numerous Euclid studies. They use the data to identify growing supermassive black holes, answer fundamental questions about galaxy evolution, and perform precise photometric measurements of young and old transient celestial objects.
Tracing out the cosmic web in Euclid’s deep fields
Euclid has scouted out the three areas in the sky where it will eventually provide the deepest observations of its mission. In just one week of observations and one scan of each region so far, Euclid spotted already 26 million galaxies. The most distant of those are up to 10.5 billion light-years away. The fields span a combined area equivalent to more than 300 times the full Moon.
In order to unravel the mysteries it is designed to explore, Euclid precisely measures the various shapes and the distribution of billions of galaxies with its high-resolution imaging visible instrument (VIS). In contrast, its near-infrared instrument (NISP) is essential for determining galaxy distances and masses.
MPE was responsible for designing and constructing the NISP near-infrared optics. In turn, MPIA carries out crucial tasks for NISP’s calibration. “MPIA engineers and scientists are developing and maintaining the mission’s entire calibration plan, calibrating and scientifically monitoring the near-infrared camera NISP, performing simulations, and conducting technical analyses such as instrument monitoring,” says MPIA’s Mischa Schirmer. He is the Euclid mission calibration and NISP calibration scientist.
The new images are a testimony to these efforts and showcase Euclid's capability of mapping hundreds of thousands of galaxies, and start to hint at the large-scale organization of these galaxies in the cosmic web.
Data processing and object classification
Euclid is expected to capture images of more than 1.5 billion galaxies over six years, sending back around 100 GB of data daily. Such an impressively large dataset creates incredible discovery opportunities, but also poses enormous challenges.
The Euclid consortium has established a European network of nine data centres, including the German Science Data Center (SDC-DE) at MPE. It is equipped with 7,000 processors and processes 10% of the data recorded by Euclid. A team of at least ten experts ensures smooth and consistent processing of astronomical imaging data. MPE’s Max Fabricius, who leads the SDC-DE, says: “Approximately 100 GB of raw data is processed virtually in real time every day. The demands on photometric precision are enormous and require a completely new approach to the methods used to calibrate the data.”
When it comes to searching for, analysing and cataloguing galaxies, the advancement of machine learning algorithms, in combination with thousands of human citizen science volunteers and experts, is playing a critical role. It is a fundamental and necessary tool to fully exploit Euclid’s vast dataset. A significant landmark in this effort is the first detailed catalogue of more than 380,000 galaxies, which have been characterized according to features such as spiral arms, central bars, and tidal tails that infer merging galaxies.
This first catalogue released today represents just 0.4% of the total number of galaxies of similar resolution expected to be imaged over Euclid’s lifetime. The final catalogue will present the detailed morphology of at least an order of magnitude more galaxies than ever measured before, helping scientists answer questions like how spiral arms form and how supermassive black holes grow.
Gravitational lensing discovery engine
Light travelling towards us from distant galaxies is bent and distorted by normal and dark matter in the foreground. This effect is called gravitational lensing and is one of Euclid’s tools to reveal how dark matter is distributed throughout the universe. When the distortions are very apparent, it is known as ‘strong lensing’, which can result in features such as Einstein rings, arcs, and multiple imaged lenses.
A first catalogue of 500 galaxy-galaxy strong lens candidates is released today, almost all previously unknown. MPIA scientists were involved in gravitational lensing classifications, labelling images with markers according to their probability of being lenses, as input for machine learning. “These AI systems will ultimately be essential for analysing the 200 times larger sky area at the end of the mission. The number of galaxies distorted by lensing will eventually increase to a staggering 100,000, about 100 times more than currently known. Human classification of individual objects will not be possible for this unprecedented dataset,” emphasizes Knud Jahnke from MPIA. He is the NISP instrument scientist.
Euclid will also be able to measure ‘weak’ lensing, when the distortions of background sources are much smaller. Such subtle distortions can only be detected by statistically analysing large numbers of galaxies. In the coming years, Euclid will measure the distorted shapes of billions of galaxies over 10 billion years of cosmic history, thus providing a 3D view of the distribution of dark matter in our universe.
Background information
As of 19 March 2025, Euclid has observed about 2000 square degrees, approximately 14% of the total survey area. The three deep fields together comprise 63.1 square degrees.
Euclid ‘quick’ releases, such as the one of 19 March, are of selected areas. They are intended to demonstrate the data products expected in the major data releases that follow, and to allow scientists to sharpen their data analysis tools in preparation. The mission’s first cosmology data will be released to the community in October 2026. Data accumulated over additional, multiple passes of the deep field locations will be included in the 2026 release.
The data release of 19 March 2025 is described in multiple scientific papers that have not yet been through the peer-review process but will be submitted to the journal Astronomy & Astrophysics.
The University of Bonn hosts the Euclid Publication Office, where the scientific publications of the Euclid Consortium are coordinated and reviewed.
About Euclid
Euclid was launched in July 2023 and started its routine science observations on 14 February 2024. It is a European mission, built and operated by the European Space Agency (ESA), with contributions from its member states and NASA. The Euclid Consortium – consisting of more than 2000 scientists from 300 institutes in 15 European countries, the USA, Canada, and Japan – is responsible for providing the scientific instruments and scientific data analysis. ESA selected Thales Alenia Space as prime contractor for constructing the satellite and its service module, with Airbus Defence and Space chosen to develop the payload module, including the telescope. NASA provided the detectors of the Near-Infrared Spectrometer and Photometer, NISP. Euclid is a medium-class mission in ESA’s Cosmic Vision Programme.
From Germany, the Max Planck Institute for Astronomy in Heidelberg, the Max Planck Institute for Extraterrestrial Physics in Garching, the Ludwig Maximilian University in Munich, the University of Bonn, the Ruhr University Bochum, the University of Bielefeld, and the German Space Agency at the German Aerospace Centre (DLR) in Bonn are participating in the Euclid project.
The German Space Agency at DLR coordinates the German ESA contributions and provides funding of 60 million euros from the National Space Programme for the participating German research institutes.
With around 21%, Germany is the most significant contributor to the ESA science programme.
This news item is based on an ESA press release that was published at the same time. Additional images are available via that release.
Method of Research
Survey
Euclid opens data treasure trove, offers glimpse of deep fields
On 19 March 2025, the European Space Agency’s Euclid mission releases its first batch of survey data, including a preview of its deep fields. Here, hundreds of thousands of galaxies in different shapes and sizes take centre stage and show a glimpse of their large-scale organisation in the cosmic web.
Covering a huge area of the sky in three mosaics, the data release also includes numerous galaxy clusters, active galactic nuclei and transient phenomena, as well as the first classification survey of more than 380 000 galaxies and 500 gravitational lens candidates compiled through combined artificial intelligence and citizen science efforts. All of this sets the scene for the broad range of topics that the dark Universe detective Euclid is set to address with its rich dataset.
“Euclid shows itself once again to be the ultimate discovery machine. It is surveying galaxies on the grandest scale, enabling us to explore our cosmic history and the invisible forces shaping our Universe,” says ESA’s Director of Science, Prof. Carole Mundell.
“With the release of the first data from Euclid’s survey, we are unlocking a treasure trove of information for scientists to dive into and tackle some of the most intriguing questions in modern science. With this, ESA is delivering on its commitment to enable scientific progress for generations to come.”
Tracing out the cosmic web in Euclid’s deep fields
Euclid has scouted out the three areas in the sky where it will eventually provide the deepest observations of its mission. In just one week of observations, with one scan of each region so far, Euclid already spotted 26 million galaxies. The farthest of those are up to 10.5 billion light-years away. The fields also contain a small population of bright quasars that can be seen much farther away. In the coming years, Euclid will pass over these three regions tens of times, capturing many more faraway galaxies, making these fields truly ‘deep’ by the end of the nominal mission in 2030.
But the first glimpse of 63 square degrees of the sky, the equivalent area of more than 300 times the full Moon, already gives an impressive preview of the scale of Euclid’s grand cosmic atlas when the mission is complete. This atlas will cover one-third of the entire sky – 14 000 square degrees – in this high-quality detail.
“It’s impressive how one observation of the deep field areas has already given us a wealth of data that can be used for a variety of purposes in astronomy: from galaxy shapes, to strong lenses, clusters, and star formation, among others,” says Valeria Pettorino, ESA’s Euclid project scientist. “We will observe each deep field between 30 and 52 times over Euclid’s six year mission, each time improving the resolution of how we see those areas, and the number of objects we manage to observe. Just think of the discoveries that await us.”
To answer the mysteries it is designed for, Euclid measures the huge variety of shapes and the distribution of billions of galaxies very precisely with its high-resolution imaging visible instrument (VIS), while its near-infrared instrument (NISP) is essential for unravelling galaxy distances and masses. The new images already showcase this capability for hundreds of thousands of galaxies, and start to hint at the large-scale organisation of these galaxies in the cosmic web. These filaments of ordinary matter and dark matter weave through the cosmos, and from these, galaxies formed and evolved. This is an essential piece in the puzzle towards understanding the mysterious nature of dark matter and dark energy, which together appear to make up 95% of the Universe.
“The full potential of Euclid to learn more about dark matter and dark energy from the large-scale structure of the cosmic web will be reached only when it has completed its entire survey. Yet the volume of this first data release already offers us a unique first glance at the large-scale organisation of galaxies, which we can use to learn more about galaxy formation over time," says Clotilde Laigle, Euclid Consortium scientist and data processing expert based at the Institut d'Astrophysique de Paris, France.
Humans and AI classify more than 380 000 galaxies
Euclid is expected to capture images of more than 1.5 billion galaxies over six years, sending back around 100 GB of data every day. Such an impressively large dataset creates incredible discovery opportunities, but huge challenges when it comes to searching for, analysing and cataloguing galaxies. The advancement of artificial intelligence (AI) algorithms, in combination with thousands of human citizen science volunteers and experts, is playing a critical role.
“We’re at a pivotal moment in terms of how we tackle large-scale surveys in astronomy. AI is a fundamental and necessary part of our process in order to fully exploit Euclid’s vast dataset,” says Mike Walmsley, Euclid Consortium scientist based at the University of Toronto, Canada, who has been heavily involved in astronomical deep learning algorithms for the last decade.
“We’re building the tools as well as providing the measurements. In this way we can deliver cutting-edge science in a matter of weeks, compared with the years-long process of analysing big surveys like these in the past,” he adds.
A major milestone in this effort is the first detailed catalogue of more than 380 000 galaxies, which have been classified according to features such as spiral arms, central bars, and tidal tails that infer merging galaxies. The catalogue is created by the ‘Zoobot’ AI algorithm. During an intensive one-month campaign on Galaxy Zoo last year, 9976 human volunteers worked together to teach Zoobot to recognise galaxy features by classifying Euclid images.
This first catalogue released today represents just 0.4% of the total number of galaxies of similar resolution expected to be imaged over Euclid’s lifetime. The final catalogue will present the detailed morphology of at least an order of magnitude more galaxies than ever measured before, helping scientists answer questions like how spiral arms form and how supermassive black holes grow.
“We’re looking at galaxies from inside to out, from how their internal structures govern their evolution to how the external environment shapes their transformation over time,” adds Clotilde.
“Euclid is a goldmine of data and its impact will be far-reaching, from galaxy evolution to the bigger-picture cosmology goals of the mission.”
Gravitational lensing discovery engine
Light travelling towards us from distant galaxies is bent and distorted by normal and dark matter in the foreground. This effect is called gravitational lensing and it is one of the tools that Euclid uses to reveal how dark matter is distributed through the Universe.
When the distortions are very apparent, it is known as ‘strong lensing’, which can result in features such as Einstein rings, arcs, and multiple imaged lenses.
Using an initial sweep by AI models, followed by citizen science inspection, expert vetting and modelling, a first catalogue of 500 galaxy-galaxy strong lens candidates is released today, almost all of which were previously unknown. This type of lensing happens when a foreground galaxy and its halo of dark matter act as a lens, distorting the image of a background galaxy along the line of sight towards Euclid.
With the help of these models, Euclid will capture some 7000 candidates in the major cosmology data release planned for the end of 2026, and in the order of 100 000 galaxy-galaxy strong lenses by the end of the mission, around 100 times more than currently known.
Euclid will also be able to measure ‘weak’ lensing, when the distortions of background sources are much smaller. Such subtle distortions can only be detected by analysing large numbers of galaxies in a statistical way. In the coming years, Euclid will measure the distorted shapes of billions of galaxies over 10 billion years of cosmic history, thus providing a 3D view of the distribution of dark matter in our Universe.
“Euclid is very quickly covering larger and larger areas of the sky thanks to its unprecedented surveying capabilities,” says Pierre Ferruit, ESA’s Euclid mission manager, who is based at ESA’s European Space Astronomy Centre (ESAC) in Spain, home of the Astronomy Science Archive where Euclid’s data will be made available.
“This data release highlights the incredible potential we have by combining the strengths of Euclid, AI, citizen science and experts into a single discovery engine that will be essential in tackling the vast volume of data returned by Euclid.”
Notes to editors
As of 19 March 2025, Euclid has observed about 2000 square degrees, approximately 14% of the total survey area (14 000 square degrees). The three deep fields together comprise 63.1 square degrees.
Euclid ‘quick’ releases, such as the one of 19 March, are of selected areas, intended to demonstrate the data products to be expected in the major data releases that follow, and to allow scientists to sharpen their data analysis tools in preparation. The mission’s first cosmology data will be released to the community in October 2026. Data accumulated over additional, multiple passes of the deep field locations will be included in the 2026 release.
The three deep field previews can now be explored in ESASky from 19 March 12:00 CET onwards:
- Euclid Deep Field South: https://sky.esa.int/esasky/?hide_welcome=true&hide_banner_info=true&hips=DES-DR2+ColorIRG&sci=false&layout=esasky&euclid_image=EDFS
- Euclid Deep Field Fornax: https://sky.esa.int/esasky/?hide_welcome=true&hide_banner_info=true&hips=PanSTARRS+DR1+color+(i%2C+r%2C+g)&sci=false&layout=esasky&euclid_image=EDFF
- Euclid Deep Field North: https://sky.esa.int/esasky/?hide_welcome=true&hide_banner_info=true&hips=PanSTARRS+DR1+color+(i%2C+r%2C+g)&sci=false&layout=esasky&euclid_image=EDFN
The data release of 19 March 2025 is described in multiple scientific papers which have not yet been through the peer-review process, but which will be submitted to the journal Astronomy & Astrophysics. A preprint of the papers is available here from 19 March 12:00 CET.
Find more detailed information about the data release here.
About Euclid
Euclid was launched in July 2023 and started its routine science observations on 14 February 2024. In November 2023 and May 2024, the world got its first glimpses of the quality of Euclid’s images, and in October 2024 the first piece of its great map of the Universe was released.
Euclid is a European mission, built and operated by ESA, with contributions from its Member States and NASA. The Euclid Consortium – consisting of more than 2000 scientists from 300 institutes in 15 European countries, the USA, Canada and Japan – is responsible for providing the scientific instruments and scientific data analysis. ESA selected Thales Alenia Space as prime contractor for the construction of the satellite and its service module, with Airbus Defence and Space chosen to develop the payload module, including the telescope. NASA provided the detectors of the Near-Infrared Spectrometer and Photometer, NISP. Euclid is a medium-class mission in ESA’s Cosmic Vision Programme.
Contact
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