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By NASA
This NASA/ESA Hubble Space Telescope image features the galaxy cluster Abell 209.ESA/Hubble & NASA, M. Postman, P. Kelly A massive, spacetime-warping cluster of galaxies is the setting of today’s NASA/ESA Hubble Space Telescope image. The galaxy cluster in question is Abell 209, located 2.8 billion light-years away in the constellation Cetus (the Whale).
This Hubble image of Abell 209 shows more than a hundred galaxies, but there’s more to this cluster than even Hubble’s discerning eye can see. Abell 209’s galaxies are separated by millions of light-years, and the seemingly empty space between the galaxies is filled with hot, diffuse gas that is visible only at X-ray wavelengths. An even more elusive occupant of this galaxy cluster is dark matter: a form of matter that does not interact with light. Dark matter does not absorb, reflect, or emit light, effectively making it invisible to us. Astronomers detect dark matter by its gravitational influence on normal matter. Astronomers surmise that the universe is comprised of 5% normal matter, 25% dark matter, and 70% dark energy.
Hubble observations, like the ones used to create this image, can help astronomers answer fundamental questions about our universe, including mysteries surrounding dark matter and dark energy. These investigations leverage the immense mass of a galaxy cluster, which can bend the fabric of spacetime itself and create warped and magnified images of background galaxies and stars in a process called gravitational lensing.
While this image lacks the dramatic rings that gravitational lensing can sometimes create, Abell 209 still shows subtle signs of lensing at work, in the form of streaky, slightly curved galaxies within the cluster’s golden glow. By measuring the distortion of these galaxies, astronomers can map the distribution of mass within the cluster, illuminating the underlying cloud of dark matter. This information, which Hubble’s fine resolution and sensitive instruments help to provide, is critical for testing theories of how our universe evolved.
Text Credit: ESA/Hubble
Image credit: ESA/Hubble & NASA, M. Postman, P. Kelly
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By European Space Agency
When the European Space Agency’s Jupiter Icy Moons Explorer (Juice) flew past our Moon in August 2024, its Radar for Icy Moon Exploration (RIME) instrument listened to radio wave echoes to reveal the height of the lunar surface.
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By NASA
Explore Hubble Hubble Home Overview About Hubble The History of Hubble Hubble Timeline Why Have a Telescope in Space? Hubble by the Numbers At the Museum FAQs Impact & Benefits Hubble’s Impact & Benefits Science Impacts Cultural Impact Technology Benefits Impact on Human Spaceflight Astro Community Impacts Science Hubble Science Science Themes Science Highlights Science Behind Discoveries Hubble’s Partners in Science Universe Uncovered Hubble and Artificial Intelligence Explore the Night Sky Observatory Hubble Observatory Hubble Design Mission Operations Missions to Hubble Hubble vs Webb Team Hubble Team Career Aspirations Hubble Astronauts Multimedia Images Videos Sonifications Podcasts e-Books Online Activities 3D Hubble Models Lithographs Fact Sheets Posters Hubble on the NASA App Glossary News Hubble News Social Media Media Resources More 35th Anniversary Online Activities 2 min read
Hubble Snaps Galaxy Cluster’s Portrait
This NASA/ESA Hubble Space Telescope image features the galaxy cluster Abell 209. ESA/Hubble & NASA, M. Postman, P. Kelly A massive, spacetime-warping cluster of galaxies is the setting of today’s NASA/ESA Hubble Space Telescope image. The galaxy cluster in question is Abell 209, located 2.8 billion light-years away in the constellation Cetus (the Whale).
This Hubble image of Abell 209 shows more than a hundred galaxies, but there’s more to this cluster than even Hubble’s discerning eye can see. Abell 209’s galaxies are separated by millions of light-years, and the seemingly empty space between the galaxies is filled with hot, diffuse gas that is visible only at X-ray wavelengths. An even more elusive occupant of this galaxy cluster is dark matter: a form of matter that does not interact with light. Dark matter does not absorb, reflect, or emit light, effectively making it invisible to us. Astronomers detect dark matter by its gravitational influence on normal matter. Astronomers surmise that the universe is comprised of 5% normal matter, 25% dark matter, and 70% dark energy.
Hubble observations, like the ones used to create this image, can help astronomers answer fundamental questions about our universe, including mysteries surrounding dark matter and dark energy. These investigations leverage the immense mass of a galaxy cluster, which can bend the fabric of spacetime itself and create warped and magnified images of background galaxies and stars in a process called gravitational lensing.
While this image lacks the dramatic rings that gravitational lensing can sometimes create, Abell 209 still shows subtle signs of lensing at work, in the form of streaky, slightly curved galaxies within the cluster’s golden glow. By measuring the distortion of these galaxies, astronomers can map the distribution of mass within the cluster, illuminating the underlying cloud of dark matter. This information, which Hubble’s fine resolution and sensitive instruments help to provide, is critical for testing theories of how our universe evolved.
Text Credit: ESA/Hubble
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Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
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Last Updated Jul 10, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Hubble Space Telescope Astrophysics Astrophysics Division Galaxies Galaxy clusters Goddard Space Flight Center Gravitational Lensing Keep Exploring Discover More Topics From Hubble
Hubble Space Telescope
Since its 1990 launch, the Hubble Space Telescope has changed our fundamental understanding of the universe.
Hubble Gravitational Lenses
Focusing in on Gravitational Lenses
Shining a Light on Dark Matter
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By NASA
6 Min Read NASA’s Chandra Shares a New View of Our Galactic Neighbor
The Andromeda galaxy, also known as Messier 31 (M31), is the closest spiral galaxy to the Milky Way at a distance of about 2.5 million light-years. Astronomers use Andromeda to understand the structure and evolution of our own spiral, which is much harder to do since Earth is embedded inside the Milky Way.
The galaxy M31 has played an important role in many aspects of astrophysics, but particularly in the discovery of dark matter. In the 1960s, astronomer Vera Rubin and her colleagues studied M31 and determined that there was some unseen matter in the galaxy that was affecting how the galaxy and its spiral arms rotated. This unknown material was named “dark matter.” Its nature remains one of the biggest open questions in astrophysics today, one which NASA’s upcoming Nancy Grace Roman Space Telescope is designed to help answer.
X-ray: NASA/CXO/UMass/Z. Li & Q.D. Wang, ESA/XMM-Newton; Infrared: NASA/JPL-Caltech/WISE, Spitzer, NASA/JPL-Caltech/K. Gordon (U. Az), ESA/Herschel, ESA/Planck, NASA/IRAS, NASA/COBE; Radio: NSF/GBT/WSRT/IRAM/C. Clark (STScI); Ultraviolet: NASA/JPL-Caltech/GALEX; Optical: Andromeda, Unexpected © Marcel Drechsler, Xavier Strottner, Yann Sainty & J. Sahner, T. Kottary. Composite image processing: L. Frattare, K. Arcand, J.Major This new composite image contains data of M31 taken by some of the world’s most powerful telescopes in different kinds of light. This image includes X-rays from NASA’s Chandra X-ray Observatory and ESA’s (European Space Agency’s) XMM-Newton (represented in red, green, and blue); ultraviolet data from NASA’s retired GALEX (blue); optical data from astrophotographers using ground based telescopes (Jakob Sahner and Tarun Kottary); infrared data from NASA’s retired Spitzer Space Telescope, the Infrared Astronomy Satellite, COBE, Planck, and Herschel (red, orange, and purple); and radio data from the Westerbork Synthesis Radio Telescope (red-orange).
The Andromeda Galaxy (M31) in Different Types of Light.X-ray: NASA/CXO/UMass/Z. Li & Q.D. Wang, ESA/XMM-Newton; Infrared: NASA/JPL-Caltech/WISE, Spitzer, NASA/JPL-Caltech/K. Gordon (U. Az), ESA/Herschel, ESA/Planck, NASA/IRAS, NASA/COBE; Radio: NSF/GBT/WSRT/IRAM/C. Clark (STScI); Ultraviolet: NASA/JPL-Caltech/GALEX; Optical: Andromeda, Unexpected © Marcel Drechsler, Xavier Strottner, Yann Sainty & J. Sahner, T. Kottary. Composite image processing: L. Frattare, K. Arcand, J.Major Each type of light reveals new information about this close galactic relative to the Milky Way. For example, Chandra’s X-rays reveal the high-energy radiation around the supermassive black hole at the center of M31 as well as many other smaller compact and dense objects strewn across the galaxy. A recent paper about Chandra observations of M31 discusses the amount of X-rays produced by the supermassive black hole in the center of the galaxy over the last 15 years. One flare was observed in 2013, which appears to represent an amplification of the typical X-rays seen from the black hole.
These multi-wavelength datasets are also being released as a sonification, which includes the same wavelengths of data in the new composite. In the sonification, the layer from each telescope has been separated out and rotated so that they stack on top of each other horizontally, beginning with X-rays at the top and then moving through ultraviolet, optical, infrared, and radio at the bottom. As the scan moves from left to right in the sonification, each type of light is mapped to a different range of notes, from lower-energy radio waves up through the high energy of X-rays. Meanwhile, the brightness of each source controls volume, and the vertical location dictates the pitch.
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In this sonification of M31, the layers from each telescope has been separated out and rotated so that they stack on top of each other horizontally beginning with X-rays at the top and then moving through ultraviolet, optical, infrared, and radio at the bottom. As the scan moves from left to right in the sonification, each type of light is mapped to a different range of notes ranging from lower-energy radio waves up through the high-energy of X-rays. Meanwhile, the brightness of each source controls volume and the vertical location dictates the pitch.NASA/CXC/SAO/K.Arcand, SYSTEM Sounds (M. Russo, A. Santaguida This new image of M31 is released in tribute to the groundbreaking legacy of Dr. Vera Rubin, whose observations transformed our understanding of the universe. Rubin’s meticulous measurements of Andromeda’s rotation curve provided some of the earliest and most convincing evidence that galaxies are embedded in massive halos of invisible material — what we now call dark matter. Her work challenged long-held assumptions and catalyzed a new era of research into the composition and dynamics of the cosmos. In recognition of her profound scientific contributions, the United States Mint has recently released a quarter in 2025 featuring Rubin as part of its American Women Quarters Program — making her the first astronomer honored in the series.
NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Chandra program. The Smithsonian Astrophysical Observatory’s Chandra X-ray Center controls science operations from Cambridge, Massachusetts, and flight operations from Burlington, Massachusetts.
Read more from NASA’s Chandra X-ray Observatory Learn more about the Chandra X-ray Observatory and its mission here:
https://www.nasa.gov/chandra
https://chandra.si.edu
Visual Description
This release features several images and a sonification video examining the Andromeda galaxy, our closest spiral galaxy neighbor. This collection helps astronomers understand the evolution of the Milky Way, our own spiral galaxy, and provides a fascinating insight into astronomical data gathering and presentation.
Like all spiral galaxies viewed at this distance and angle, Andromeda appears relatively flat. Its spiraling arms circle around a bright core, creating a disk shape, like a large dinner plate. In most of the images in this collection, Andromeda’s flat surface is tilted to face our upper left.
This collection features data from some of the world’s most powerful telescopes, each capturing light in a different spectrum. In each single-spectrum image, Andromeda has a similar shape and orientation, but the colors and details are dramatically different.
In radio waves, the spiraling arms appear red and orange, like a burning, loosely coiled rope. The center appears black, with no core discernible. In infrared light, the outer arms are similarly fiery. Here, a white spiraling ring encircles a blue center with a small golden core. The optical image is hazy and grey, with spiraling arms like faded smoke rings. Here, the blackness of space is dotted with specks of light, and a small bright dot glows at the core of the galaxy. In ultraviolet light the spiraling arms are icy blue and white, with a hazy white ball at the core. No spiral arms are present in the X-ray image, making the bright golden core and nearby stars clear and easy to study.
In this release, the single-spectrum images are presented side by side for easy comparison. They are also combined into a composite image. In the composite, Andromeda’s spiraling arms are the color of red wine near the outer edges, and lavender near the center. The core is large and bright, surrounded by a cluster of bright blue and green specks. Other small flecks in a variety of colors dot the galaxy, and the blackness of space surrounding it.
This release also features a thirty second video, which sonifies the collected data. In the video, the single-spectrum images are stacked vertically, one atop the other. As the video plays, an activation line sweeps across the stacked images from left to right. Musical notes ring out when the line encounters light. The lower the wavelength energy, the lower the pitches of the notes. The brighter the source, the louder the volume.
News Media Contact
Megan Watzke
Chandra X-ray Center
Cambridge, Mass.
617-496-7998
mwatzke@cfa.harvard.edu
Lane Figueroa
Marshall Space Flight Center, Huntsville, Alabama
256-544-0034
lane.e.figueroa@nasa.gov
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Last Updated Jun 25, 2025 EditorLee MohonContactLane Figueroa Related Terms
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NASA-Assisted Scientists Get Bird’s-Eye View of Population Status
Through the eBird citizen scientist program, millions of birders have recorded their observations of different species and submitted checklists to the Cornell Lab of Ornithology. Through a partnership with NASA, the lab has now used this data to model and map bird population trends for nearly 500 North American species.
Led by Alison Johnston of the University of St. Andrews in Scotland, the researchers reported that 75% of bird species in the study are declining at wide-range scales. And yet this study has some good news for birds. The results, published in Science in May, offer insights and projections that could shape the future conservation of the places where birds make their homes.
“This project demonstrates the power of merging in situ data with NASA remote sensing to model biological phenomena that were previously impossible to document,” said Keith Gaddis, NASA’s Biological Diversity and Ecological Forecasting program manager at the agency’s headquarters in Washington, who was not involved in the study. “This data provides not just insight into the Earth system but also provides actionable guidance to land managers to mitigate biodiversity loss.”
Rock wren in Joshua Tree National Park. National Park Service / Jane Gamble A team from Cornell, the University of St. Andrews, and the American Bird Conservancy used land imaging data from NASA’s Moderate Resolution Imaging Spectroradiometer (MODIS) instruments to distinguish among such specific bird habitats as open forests, dense shrublands, herbaceous croplands, and forest/cropland mosaics. They also drew on NASA weather information and water data that matched the dates and times when birders made their reports.
When combined with a 14-year set of eBird checklists — 36 million sets of species observations and counts, keyed directly to habitats — the satellite data gave researchers almost a strong foundation to produce a clear picture of the health of bird populations. But there was one missing piece.
Wrestling with Wren Data
While some eBird checklists come from expert birders who’ve hiked deep into wildlife preserves, others are sent in by novices watching bird feeders and doing the dishes. This creates what Cornell statistician Daniel Fink described as “an unstructured, very noisy data set,” complete with gaps in the landscape that birders did not reach and, ultimately, some missing birds.
To account for gaps where birds weren’t counted, the researchers trained machine learning models to fill in the maps based on the remote sensing data. “For every single species — say the rock wren — we’ve created a simulation that mimics the species and a variety of ways that it could respond to changes in the environment,” Johnston said. “Thousands of simulations underlie the results we showed.”
CornellLab eBird The researchers achieved unprecedented resolution, zeroing in on areas 12 miles by 12 miles (27 km by 27 km), the same area as Portland, Oregon. This new population counting method can also be applied to eBird data from other locations, Fink said. “Now we’re using modeling to track bird populations — not seasonally through the year, but acrossthe years — a major milestone,” he added.
“We’ve been able to take citizen science data and, through machine learning methodology, put it on the same footing as traditionally structured surveys, in terms of the type of signal we can find,” said Cornell science product manager Tom Auer. “It will increase the credibility and confidence of people who use this information for precise conservation all over the globe.”
The Up Side
Since 1970, North America has lost one-quarter of its breeding birds, following a global trend of declines across species. The causes range from increased pollution and land development to changing climate and decreased food resources. Efforts to reverse this loss depend on identifying the areas where birds live at highest risk, assessing their populations, and pinpointing locations where conservation could help most.
For 83% of the reported species in the new study, the decline was greatest in spots where populations had previously been most abundant — indicating problems with the habitat.
“Even in species where populations are declining a lot, there are still places of hope, where the populations are going up,” Johnston said. The team found population increases in the maps of 97% of the reported species. “That demonstrates that there’s opportunity for those species.”
“Birds face so many challenges,” said Cornell conservationist Amanda Rodewald. “This research will help us make strategic decisions about making changes that are precise, effective, and less costly. This is transformative. Now we can really drill in and know where specifically we’re going to be able to have the most positive impact in trying to stem bird declines.”
By Karen Romano Young
NASA Headquarters, Washington
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Last Updated Jun 25, 2025 Related Terms
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