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A new look at the heart of our Milky Way galaxy by Euclid, an ESA (European Space Agency) mission with NASA contributions, overlaps with a region scientists will observe with NASA\u2019s Nancy Grace Roman Space Telescope, launching later this summer. This sneak peek gives astronomers a major jumpstart on a core Roman survey, helping scientists learn more than they could from either telescope alone.\u00a0<\/p>\n
\u201cThis is the only time Euclid has paused its normal sky survey, which is mainly geared toward cosmology,\u201d said Jason Rhodes, a senior research scientist at NASA\u2019s Jet Propulsion Laboratory in Southern California. Rhodes serves as both the U.S. Euclid science lead and the NASA JPL Roman project scientist. \u201cThis takes a lot of work and planning, so it really has to be something with a high impact for science. Adding Euclid\u2019s snapshot to Roman\u2019s future survey will help us map our galaxy better and identify hard-to-find cosmic treasures like isolated black holes and rogue planets more easily.\u201d<\/p>\n
Euclid took one day out from its six-year prime mission to preview the area of sky that will be targeted by Roman\u2019s Galactic Bulge Time-Domain Survey<\/a>, which will provide one of the deepest views ever into the center of our galaxy. Though Euclid\u2019s one-time observation is shallower and lacks some of the color detail Roman will see, it has similar resolution and covers a larger region \u2014 about 5 square degrees, or the sky area covered by about 25 full moons \u2014 since Roman\u2019s survey area hadn\u2019t yet been determined when the observation took place in March 2025.<\/p>\n Over the course of its five-year primary mission, Roman will repeatedly image a smaller region (1.7 square degrees, or roughly the sky area covered by 8.5 full moons) to watch how hundreds of millions of stars and other objects change over short time periods<\/a>. Monitoring these changes will reveal hordes of new planets, along with many other cosmic objects and phenomena. Stitching Euclid\u2019s observation onto the front end of Roman\u2019s collection will essentially extend the survey by two years (since Roman\u2019s galactic bulge observations are set to begin in spring 2027), making even more science possible.<\/p>\n Mining hidden gems<\/strong><\/p>\n Roman will watch for tiny surges in starlight that herald a microlensing event. This light-bending phenomenon occurs when a massive object like a star, planet, or black hole \u2014 any object with sufficient gravity \u2014 closely aligns with a background star from our vantage point. Light from the distant star curves as it travels through the warped space-time caused by the nearer object\u2019s mass.<\/p>\n If the alignment is especially close, the nearer object acts like a cosmic lens, focusing and magnifying light from the background star.<\/p>\n \u201cMost often, the lensing object is another star,\u201d said Matthew Penny, an assistant professor at Louisiana State University, and co-lead of Euclid\u2019s exoplanet science working group who has spent more than a decade simulating both Euclid and Roman data. \u201cBut Roman will also be able to detect planets orbiting them, and all kinds of weird objects that are nearly impossible to find any other way.\u201d<\/p>\n Among those strange objects are black holes left behind after the most massive stars die. Astronomers think there should be about 100 million of these stellar-mass black holes in the Milky Way, but so far they\u2019ve almost exclusively detected the invisible objects when they interact with a companion star. Yet most are thought to wander the galaxy alone. Roman will find them<\/a> even when there\u2019s nothing nearby to reveal their presence.<\/p>\n While microlensing events created by planets are typically hours or days long, black holes pack in so much mass that they can bend light over a larger region of space, creating much longer signals. That means astronomers may need to observe them for years to see the objects move out of alignment.<\/p>\n \u201cThe extra two years provided by Euclid give astronomers more time to watch the lens and source star drift apart, making it easier to identify the lens and measure its mass,\u201d said Himanshu Verma, a postdoctoral researcher at Louisiana State University who has been analyzing Euclid images to help scientists predict and better understand the microlensing events Roman is expected to observe.<\/p>\n While most planet-hunting methods are best at finding scorching worlds tightly hugging their host star, microlensing is better at detecting worlds in orbits larger than Earth\u2019s. That includes planets that whirl around their stars farther away than Neptune orbits the Sun and ones that have been kicked out of their original star systems altogether, now destined to roam the galaxy all alone<\/a>.<\/p>\n \u201cWhen Roman finds them, astronomers will be able to cross-reference Euclid\u2019s earlier observations to look for stars near the lensing object, so we can confirm whether a planet is truly rogue or just orbiting very far from its host star,\u201d said David Bennett, a senior research scientist and microlensing expert at the University of Maryland, College Park and NASA\u2019s Goddard Space Flight Center.<\/p>\n Milky Way mapping<\/strong><\/p>\n Scientists will also pair Euclid data with Roman\u2019s Galactic Plane Survey<\/a>. This observation program will reveal our home galaxy in unprecedented detail over an area about 400 times larger than the galactic bulge survey. In one month of observations spread across two years, the Roman survey will unveil tens of billions of stars and explore previously uncharted structures.<\/p>\n It\u2019s tricky to study our own galaxy because it\u2019s like trying to map the human body from inside a cell; there\u2019s a lot of stuff in the way. Combining Euclid\u2019s observations with Roman\u2019s will let astronomers watch stars slowly move across the sky. Since stars in different parts of the Milky Way tend to follow different paths, this will help astronomers figure out which part of the galaxy those stars are in.<\/p>\n \u201cOne of the most exciting aspects of the Euclid observations is that they give us the chance to test and improve Milky Way models,\u201d Penny said.<\/p>\n Euclid\u2019s one-day detour offers a scientific payout that will last for years and shows how much more can emerge when telescopes team up.<\/p>\n \u201cWe\u2019ve shown that these two telescopes can work together to do science that surpasses what either was originally designed for,\u201d Rhodes said. \u201cIn doing so, we\u2019ve established a model for future coordinated observations that can unlock far more discoveries than either mission could make alone.\u201d<\/p>\n To learn more about the Roman mission, visit:<\/p>\n https:\/\/www.nasa.gov\/roman<\/strong><\/a><\/p>\n Media contact:<\/strong><\/p>\n Claire Andreoli<\/a>
NASA\u2019s Goddard Space Flight Center<\/a>, Greenbelt, Md.
301-286-1940<\/strong><\/p>\n<\/div>\n