{"id":234472,"date":"2025-06-13T01:48:00","date_gmt":"2025-06-12T15:48:00","guid":{"rendered":"https:\/\/www.nasa.gov\/?p=875944"},"modified":"2025-06-13T01:48:00","modified_gmt":"2025-06-12T15:48:00","slug":"nasas-roman-to-peer-into-cosmic-lenses-to-better-define-dark-matter","status":"publish","type":"post","link":"https:\/\/www.vibewire.com.au\/?p=234472","title":{"rendered":"NASA\u2019s Roman to Peer Into Cosmic \u2018Lenses\u2019 to Better Define Dark Matter"},"content":{"rendered":"

A funky effect Einstein predicted, known as gravitational lensing<\/a> \u2014 when a foreground galaxy magnifies more distant galaxies behind it \u2014 will soon become common when NASA\u2019s Nancy Grace Roman Space Telescope begins science operations in 2027 and produces vast surveys of the cosmos.<\/p>\n

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This image shows a simulated observation from NASA\u2019s Nancy Grace Roman Space Telescope with an overlay of its Wide Field Instrument\u2019s 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\u2019s 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\u2019s 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.<\/div>\n
Credit: NASA, Bryce Wedig (Washington University), Tansu Daylan (Washington University), Joseph DePasquale (STScI)<\/div>\n<\/figcaption><\/div>\n<\/div>\n<\/div>\n

A particular subset of gravitational lenses, known as strong lenses, is the focus of a new paper <\/a>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\u2019s vast images. Each Roman image will be 200 times larger than infrared snapshots from NASA\u2019s Hubble Space Telescope, and its upcoming \u201cwealth\u201d of lenses will vastly outpace the hundreds studied by Hubble to date.<\/p>\n

Roman will conduct three core surveys<\/a>, providing expansive views of the universe. This science team\u2019s work is based on a previous version of Roman\u2019s now fully defined High-Latitude Wide-Area Survey<\/a>. The researchers are working on a follow-up paper that will align with the final survey\u2019s specifications to fully support the research community.<\/p>\n

\u201cThe current sample size of these objects from other telescopes is fairly small because we\u2019re relying on two galaxies to be lined up nearly perfectly along our line of sight,\u201d Wedig said. \u201cOther telescopes are either limited to a smaller field of view or less precise observations, making gravitational lenses harder to detect.\u201d<\/p>\n

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.<\/p>\n

\u201cRoman will not only significantly increase our sample size \u2014 its sharp, high-resolution images will also allow us to discover gravitational lenses that appear smaller on the sky,\u201d 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<\/a> at Washington University in St. Louis. \u201cUltimately, 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.\u201d<\/p>\n

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This video shows how a background galaxy\u2019s light is lensed or magnified by a massive foreground galaxy, seen at center, before reaching NASA\u2019s 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.<\/div>\n<\/div>\n
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Credit: NASA, Joseph Olmsted (STScI)<\/div>\n<\/div>\n<\/div>\n<\/div>\n

What Is Dark Matter?<\/strong><\/h3>\n

Not all mass in galaxies is made up of objects we can see, like star clusters. A significant fraction of a galaxy\u2019s mass is made up of dark matter<\/a>, so called because it doesn\u2019t emit, reflect, or absorb light. Dark matter does, however, possess mass, and like anything else with mass, it can cause gravitational lensing.<\/p>\n

When the gravity of a foreground galaxy bends the path of a background galaxy\u2019s light, its light is routed onto multiple paths. \u201cThis effect produces multiple images of the background galaxy that are magnified and distorted differently,\u201d Daylan said. These \u201cduplicates\u201d are a huge advantage for researchers \u2014 they allow multiple measurements of the lensing galaxy\u2019s mass distribution, ensuring that the resulting measurement is far more precise.<\/p>\n

Roman\u2019s 300-megapixel camera, known as its Wide Field Instrument<\/a>, will allow researchers to accurately determine the bending of the background galaxies\u2019 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.<\/p>\n

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 \u2014 the types of structures that gradually merged over time to build up the galaxies we see today.<\/p>\n

With Roman, the team will accumulate overwhelming statistics about the size and structures of early galaxies. \u201cFinding 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,\u201d Wedig said. \u201cWe won\u2019t see dark matter in the images \u2014 it\u2019s invisible \u2014 but we can measure its effects.\u201d<\/p>\n

\u201cUltimately, the question we\u2019re trying to address is: What particle or particles constitute dark matter?\u201d Daylan added. \u201cWhile 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.\u201d<\/p>\n

Preparations Continue<\/strong><\/h3>\n

Before Roman launches, the team will also search for more candidates in observations from ESA\u2019s (the European Space Agency\u2019s) 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\u2019s infrared images are in hand, the researchers will combine them with complementary visible light images from Euclid, Rubin, and Hubble to maximize what\u2019s known about these galaxies.<\/p>\n

\u201cWe 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,\u201d Daylan said.<\/p>\n

The Nancy Grace Roman Space Telescope is managed at NASA\u2019s 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.<\/p>\n

By Claire Blome
Space Telescope Science Institute, Baltimore, Md.<\/strong><\/p>\n

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