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Ready, set, go! Euclid begins its dark Universe survey
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By NASA
A funky effect Einstein predicted, known as gravitational lensing — when a foreground galaxy magnifies more distant galaxies behind it — will soon become common when NASA’s Nancy Grace Roman Space Telescope begins science operations in 2027 and produces vast surveys of the cosmos.
This image shows a simulated observation from NASA’s Nancy Grace Roman Space Telescope with an overlay of its Wide Field Instrument’s field of view. More than 20 gravitational lenses, with examples shown at left and right, are expected to pop out in every one of Roman’s vast observations. A journal paper led by Bryce Wedig, a graduate student at Washington University in St. Louis, Missouri, estimates that of those Roman detects, about 500 from the telescope’s High-Latitude Wide-Area Survey will be suitable for dark matter studies. By examining such a large population of gravitational lenses, the researchers hope to learn a lot more about the mysterious nature of dark matter.Credit: NASA, Bryce Wedig (Washington University), Tansu Daylan (Washington University), Joseph DePasquale (STScI) A particular subset of gravitational lenses, known as strong lenses, is the focus of a new paper published in the Astrophysical Journal led by Bryce Wedig, a graduate student at Washington University in St. Louis. The research team has calculated that over 160,000 gravitational lenses, including hundreds suitable for this study, are expected to pop up in Roman’s vast images. Each Roman image will be 200 times larger than infrared snapshots from NASA’s Hubble Space Telescope, and its upcoming “wealth” of lenses will vastly outpace the hundreds studied by Hubble to date.
Roman will conduct three core surveys, providing expansive views of the universe. This science team’s work is based on a previous version of Roman’s now fully defined High-Latitude Wide-Area Survey. The researchers are working on a follow-up paper that will align with the final survey’s specifications to fully support the research community.
“The current sample size of these objects from other telescopes is fairly small because we’re relying on two galaxies to be lined up nearly perfectly along our line of sight,” Wedig said. “Other telescopes are either limited to a smaller field of view or less precise observations, making gravitational lenses harder to detect.”
Gravitational lenses are made up of at least two cosmic objects. In some cases, a single foreground galaxy has enough mass to act like a lens, magnifying a galaxy that is almost perfectly behind it. Light from the background galaxy curves around the foreground galaxy along more than one path, appearing in observations as warped arcs and crescents. Of the 160,000 lensed galaxies Roman may identify, the team expects to narrow that down to about 500 that are suitable for studying the structure of dark matter at scales smaller than those galaxies.
“Roman will not only significantly increase our sample size — its sharp, high-resolution images will also allow us to discover gravitational lenses that appear smaller on the sky,” said Tansu Daylan, the principal investigator of the science team conducting this research program. Daylan is an assistant professor and a faculty fellow at the McDonnell Center for the Space Sciences at Washington University in St. Louis. “Ultimately, both the alignment and the brightness of the background galaxies need to meet a certain threshold so we can characterize the dark matter within the foreground galaxies.”
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This video shows how a background galaxy’s light is lensed or magnified by a massive foreground galaxy, seen at center, before reaching NASA’s Roman Space Telescope. Light from the background galaxy is distorted, curving around the foreground galaxy and appearing more than once as warped arcs and crescents. Researchers studying these objects, known as gravitational lenses, can better characterize the mass of the foreground galaxy, which offers clues about the particle nature of dark matter.Credit: NASA, Joseph Olmsted (STScI) What Is Dark Matter?
Not all mass in galaxies is made up of objects we can see, like star clusters. A significant fraction of a galaxy’s mass is made up of dark matter, so called because it doesn’t emit, reflect, or absorb light. Dark matter does, however, possess mass, and like anything else with mass, it can cause gravitational lensing.
When the gravity of a foreground galaxy bends the path of a background galaxy’s light, its light is routed onto multiple paths. “This effect produces multiple images of the background galaxy that are magnified and distorted differently,” Daylan said. These “duplicates” are a huge advantage for researchers — they allow multiple measurements of the lensing galaxy’s mass distribution, ensuring that the resulting measurement is far more precise.
Roman’s 300-megapixel camera, known as its Wide Field Instrument, will allow researchers to accurately determine the bending of the background galaxies’ light by as little as 50 milliarcseconds, which is like measuring the diameter of a human hair from the distance of more than two and a half American football fields or soccer pitches.
The amount of gravitational lensing that the background light experiences depends on the intervening mass. Less massive clumps of dark matter cause smaller distortions. As a result, if researchers are able to measure tinier amounts of bending, they can detect and characterize smaller, less massive dark matter structures — the types of structures that gradually merged over time to build up the galaxies we see today.
With Roman, the team will accumulate overwhelming statistics about the size and structures of early galaxies. “Finding gravitational lenses and being able to detect clumps of dark matter in them is a game of tiny odds. With Roman, we can cast a wide net and expect to get lucky often,” Wedig said. “We won’t see dark matter in the images — it’s invisible — but we can measure its effects.”
“Ultimately, the question we’re trying to address is: What particle or particles constitute dark matter?” Daylan added. “While some properties of dark matter are known, we essentially have no idea what makes up dark matter. Roman will help us to distinguish how dark matter is distributed on small scales and, hence, its particle nature.”
Preparations Continue
Before Roman launches, the team will also search for more candidates in observations from ESA’s (the European Space Agency’s) Euclid mission and the upcoming ground-based Vera C. Rubin Observatory in Chile, which will begin its full-scale operations in a few weeks. Once Roman’s infrared images are in hand, the researchers will combine them with complementary visible light images from Euclid, Rubin, and Hubble to maximize what’s known about these galaxies.
“We will push the limits of what we can observe, and use every gravitational lens we detect with Roman to pin down the particle nature of dark matter,” Daylan said.
The Nancy Grace Roman Space Telescope is managed at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, with participation by NASA’s Jet Propulsion Laboratory in Southern California; Caltech/IPAC in Pasadena, California; the Space Telescope Science Institute in Baltimore; and a science team comprising scientists from various research institutions. The primary industrial partners are BAE Systems, Inc. in Boulder, Colorado; L3Harris Technologies in Melbourne, Florida; and Teledyne Scientific & Imaging in Thousand Oaks, California.
By Claire Blome
Space Telescope Science Institute, Baltimore, Md.
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Last Updated Jun 12, 2025 EditorAshley BalzerContactAshley Balzerashley.m.balzer@nasa.govLocationNASA Goddard Space Flight Center Related Terms
Nancy Grace Roman Space Telescope Astrophysics Dark Matter Galaxies Galaxies, Stars, & Black Holes Galaxies, Stars, & Black Holes Research The Universe Explore More
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By European Space Agency
Video: 00:02:00 ESA project astronaut Sławosz Uznański-Wiśniewski is heading to the International Space Station on his first mission as part of Axiom Mission 4 (Ax-4). He is the second ESA project astronaut from a new generation of Europeans to fly on a commercial human spaceflight mission with Axiom Space.
Sponsored by the Polish government and supported by ESA, the Polish Ministry of Economic Development and Technology (MRiT), and the Polish Space Agency (POLSA), the mission—called Ignis—features an ambitious technological and scientific programme. It includes several experiments proposed by the Polish space industry and developed in cooperation with ESA, along with additional ESA-led experiments.
Follow Sławosz's journey on the Ignis mission website and discover more about the next mission patch to be hung on the walls of the Columbus Control Centre.
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By NASA
A new online portal by NASA and the Alaska Satellite Facility maps satellite radar meas-urements across North America, enabling users to track land movement since 2016 caused by earthquakes, landslides, volcanoes, and other phenomena.USGS An online tool maps measurements and enables non-experts to understand earthquakes, subsidence, landslides, and other types of land motion.
NASA is collaborating with the Alaska Satellite Facility in Fairbanks to create a powerful web-based tool that will show the movement of land across North America down to less than an inch. The online portal and its underlying dataset unlock a trove of satellite radar measurements that can help anyone identify where and by how much the land beneath their feet may be moving — whether from earthquakes, volcanoes, landslides, or the extraction of underground natural resources such as groundwater.
Spearheaded by NASA’s Observational Products for End-Users from Remote Sensing Analysis (OPERA) project at the agency’s Jet Propulsion Laboratory in Southern California, the effort equips users with information that would otherwise take years of training to produce. The project builds on measurements from spaceborne synthetic aperture radars, or SARs, to generate high-resolution data on how Earth’s surface is moving.
The OPERA portal shows how land is sinking in Freshkills Park, which is being built on the site of a former landfill on Staten Island, New York. Landfills tend to sink over time as waste decomposes and settles. The blue dot marks the spot where the portal is showing movement in the graph.Alaska Satellite Facility Formally called the North America Surface Displacement Product Suite, the new dataset comes ready to use with measurements dating to 2016, and the portal allows users to view those measurements at a local, state, and regional scales in a few seconds. For someone not using the dataset or website, it could take days or longer to do a similar analysis.
“You can zoom in to your country, your state, your city block, and look at how the land there is moving over time,” said David Bekaert, the OPERA project manager and a JPL radar scientist. “You can see that by a simple mouse click.”
The portal currently includes measurements for millions of pixels across the U.S. Southwest, northern Mexico, and the New York metropolitan region, each representing a 200-foot-by-200-foot (60-meter-by-60-meter) area on the ground. By the end of 2025, OPERA will add data to cover the rest of the United States, Central America, and Canada within 120 miles (200 kilometers) of the U.S. border. When a user clicks on a pixel, the system pulls measurements from hundreds of files to create a graph visualizing the land surface’s cumulative movement over time.
Land is rising at the Colorado River’s outlet to the Gulf of California, as indicated in this screenshot from the OPERA portal. The uplift is due to the sediment from the river building up over time. The graph shows that the land at the blue dot has risen about 8 inches (20 centimeters) since 2016.Alaska Satellite Facility “The OPERA project automated the end-to-end SAR data processing system such that users and decision-makers can focus on discovering where the land surface may be moving in their areas of interest,” said Gerald Bawden, program scientist responsible for OPERA at NASA Headquarters in Washington. “This will provide a significant advancement in identifying and understanding potential threats to the end users, while providing cost and time savings for agencies.”
For example, water-management bureaus and state geological surveys will be able to directly use the OPERA products without needing to make big investments in data storage, software engineering expertise, and computing muscle.
How It Works
To create the displacement product, the OPERA team continuously draws data from the ESA (European Space Agency) Sentinel-1 radar satellites, the first of which launched in 2014. Data from NISAR, the NASA-ISRO (Indian Space Research Organisation) Synthetic Aperture Radar mission, will be added to the mix after that spacecraft launches later this year.
The OPERA portal shows that land near Willcox, Arizona, subsided about 8 inches (20 centimeters) since between 2016 and 2021, in large part due to groundwater pumping. The region is part of an area being managed by state water officials.Alaska Satellite Facility Satellite-borne radars work by emitting microwave pulses at Earth’s surface. The signals scatter when they hit land and water surfaces, buildings, and other objects. Raw data consists of the strength and time delay of the signals that echo back to the sensor.
To understand how land in a given area is moving, OPERA algorithms automate steps in an otherwise painstaking process. Without OPERA, a researcher would first download hundreds or thousands of data files, each representing a pass of the radar over the point of interest, then make sure the data aligned geographically over time and had precise coordinates.
Then they would use a computationally intensive technique called radar interferometry to gauge how much the land moved, if at all, and in which direction — towards the satellite, which would indicate the land rose, or away from the satellite, which would mean it sank.
“The OPERA project has helped bring that capability to the masses, making it more accessible to state and federal agencies, and also users wondering, ‘What’s going on around my house?’” said Franz Meyer, chief scientist of the Alaska Satellite Facility, a part of the University of Alaska Fairbanks Geophysical Institute.
Monitoring Groundwater
Sinking land is a top priority to the Arizona Department of Water Resources. From the 1950s through the 1980s, it was the main form of ground movement officials saw, as groundwater pumping increased alongside growth in the state’s population and agricultural industry. In 1980, the state enacted the Groundwater Management Act, which reduced its reliance on groundwater in highly populated areas and included requirements to monitor its use.
The department began to measure this sinking, called subsidence, with radar data from various satellites in the early 2000s, using a combination of SAR, GPS-based monitoring, and traditional surveying to inform groundwater-management decisions.
Now, the OPERA dataset and portal will help the agency share subsidence information with officials and community members, said Brian Conway, the department’s principal hydrogeologist and supervisor of its geophysics unit. They won’t replace the SAR analysis he performs, but they will offer points of comparison for his calculations. Because the dataset and portal will cover the entire state, they also could identify areas not yet known to be subsiding.
“It’s a great tool to say, ‘Let’s look at those areas more intensely with our own SAR processing,’” Conway said.
The displacement product is part of a series of data products OPERA has released since 2023. The project began in 2020 with a multidisciplinary team of scientists at JPL working to address satellite data needs across different federal agencies. Through the Satellite Needs Working Group, those agencies submitted their requests, and the OPERA team worked to improve access to information to aid a range of efforts such as disaster response, deforestation tracking, and wildfire monitoring.
NASA-Led Project Tracking Changes to Water, Ecosystems, Land Surface News Media Contacts
Andrew Wang / Jane J. Lee
Jet Propulsion Laboratory, Pasadena, Calif.
626-379-6874 / 818-354-0307
andrew.wang@jpl.nasa.gov / jane.j.lee@jpl.nasa.gov
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Last Updated Jun 06, 2025 Related Terms
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By European Space Agency
The European Space Agency’s (ESA) newest planetary defender has opened its ‘eye’ to the cosmos for the first time. The Flyeye telescope’s ‘first light’ marks the beginning of a new chapter in how we scan the skies for new near-Earth asteroids and comets.
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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 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 Spies Paired Pinwheel on Its Own
This NASA Hubble Space Telescope image features the beautiful barred spiral galaxy NGC 3507 ESA/Hubble & NASA, D. Thilker A single member of a galaxy pair takes centerstage in this NASA/ESA Hubble Space Telescope image. This beautiful spiral galaxy is NGC 3507, which is situated about 46 million light-years away in the constellation Leo (the Lion). NGC 3507’s classification is a barred spiral because the galaxy’s sweeping spiral arms emerge from the ends of a central bar of stars rather than the central core of the galaxy.
Though pictured solo here, NGC 3507 actually travels the universe with a galactic partner named NGC 3501 that is located outside the frame. While NGC 3507 is a quintessential galactic pinwheel, its partner resembles a streak of quicksilver across the sky. Despite looking completely different, both are spiral galaxies, simply seen from different angles.
For galaxies that are just a few tens of millions of light-years away, like NGC 3507 and NGC 3501, features like spiral arms, dusty gas clouds, and brilliant star clusters are on full display. More distant galaxies appear less detailed. See if you can spot any faraway galaxies in this image: they tend to be orange or yellow and can be anywhere from circular and starlike to narrow and elongated, with hints of spiral arms. Astronomers use instruments called spectrometers to split the light from these distant galaxies to study the nature of these objects in the early universe.
In addition to these far-flung companions, a much nearer object joins NGC 3507. The object is marked by four spikes of light: a star within the Milky Way, a mere 436 light-years away from Earth.
Text Credit: ESA/Hubble
Facebook logo @NASAHubble @NASAHubble Instagram logo @NASAHubble Media Contact:
Claire Andreoli (claire.andreoli@nasa.gov)
NASA’s Goddard Space Flight Center, Greenbelt, MD
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Last Updated May 30, 2025 Editor Andrea Gianopoulos Location NASA Goddard Space Flight Center Related Terms
Hubble Space Telescope Astrophysics Astrophysics Division Galaxies Goddard Space Flight Center Spiral Galaxies The Universe Keep Exploring Discover More Topics From Hubble
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