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NASA\u2019s Neil Gehrels Swift Observatory captured an \u201corphan\u201d black hole lighting up as it devoured a star on the outskirts of a faraway galaxy. These phenomena are rare to begin with, and none had ever before been seen so far outside of a galaxy\u2019s core.<\/p>\n
\u201cWe were looking for these star-shredding events as a way to find otherwise invisible supermassive black holes wandering away from the galactic cores where they usually reside,\u201d said Robert Stein, a research fellow at The University of Maryland, College Park and NASA\u2019s Goddard Space Flight Center in Greenbelt, Maryland. \u201cWith this discovery, which is one of just a couple that have been confirmed so far, we\u2019ve validated a new technique and can use it to hunt for more.\u201d<\/p>\n
A paper<\/a> describing the results, led by Stein, was published Monday in The Astrophysical Journal Letters.<\/p>\n Researchers saw an ultrabright flare unleashed by a star being torn apart by extreme gravitational forces after drifting too close to a monster black hole \u2014 a phenomenon called a tidal disruption event. The black hole behind the blast weighs in at about a million times the Sun\u2019s mass. Its existence was first flagged in November 2025 as an unusual brightening in a galaxy about 750 million light-years away by ZTF (Zwicky Transient Facility), a survey conducted by the Palomar Observatory in Southern California.<\/p>\n \u201cOut of the half million flashes ZTF detects each night, our new artificial intelligence algorithm automatically recognized a flare that looked a lot like a tidal disruption event, despite its unusual location in the outskirts of a galaxy,\u201d Stein said. For a few months, the tidal disruption event outshone its entire host galaxy in ultraviolet wavelengths, temporarily radiating with the light of about 10 billion suns.<\/p>\n Other telescopes, including the SOAR (Southern Astrophysical Research) telescope in Chile, followed up on the ZTF source to look at the event\u2019s spectrum, which revealed features supporting that it was likely a tidal disruption event. Astronomers then used NASA\u2019s Swift to look at wavelengths they can\u2019t detect with ground-based telescopes to uncover new information. For example, Swift\u2019s UVOT (Ultraviolet\/Optical Telescope) took the blip\u2019s temperature and found that it had quite a fever at about 54,000 degrees Fahrenheit (30,000 degrees Celsius).<\/p>\n \u201cThe combination of all this data helped us rule out other explanations and confidently say it\u2019s a tidal disruption event, despite its strange location,\u201d said Jonathan Carney, a doctoral student at the University of North Carolina at Chapel Hill, who took the first spectra that supported the flare\u2019s interpretation as a tidal disruption event.<\/p>\n Nearly every galaxy in the universe is anchored by a supermassive black hole sitting right in the center. About once every 100,000 years, a star will drift too close to this invisible heavyweight and trigger a tidal disruption event.<\/p>\n While they\u2019re rather rare in any given galaxy, scientists scour millions of galaxies for them. Each year, astronomical surveys typically spot about 30 tidal disruption events occurring somewhere in the universe.<\/p>\n Prior to 2024, they\u2019d only been seen in galaxy cores. That\u2019s partly because astronomers mainly looked for them there; after all, it\u2019s where all the known supermassive black holes were, and you can\u2019t get a tidal disruption event without one (the gravitational pull of lighter black holes isn\u2019t strong enough).<\/p>\n Then scientists saw the telltale signs of a star being shredded<\/a> 2,600 light-years from the center of its host galaxy. That inspired more astronomers to look beyond galaxy cores for similar events, and now a team has identified one more than 30,000 light-years away from a galaxy\u2019s center.<\/p>\n So how did the newfound black hole become so off-kilter?<\/p>\n \u201cIt must have originated in a galaxy\u2019s center, but not the one it\u2019s in the outskirts of now,\u201d Stein said. \u201cWe think the host galaxy\u2019s supermassive black hole is still at its core, but the one eating the star could have started off in a small galaxy that merged with the big one we see today.\u201d<\/p>\n The researchers have outlined two possibilities. Three or more galaxies may have merged together, and the gravitational tug-of-war between their central supermassive black holes may have flung the lightest black hole out to the galaxy\u2019s edge.<\/p>\n Or a dwarf galaxy could be midway through a merger. As the dwarf\u2019s stars fell into the larger galaxy, one may have passed too close to the dwarf\u2019s supermassive black hole.<\/p>\n \u201cFurther discoveries could reveal the origin of this apparent \u2018orphan\u2019 black hole,\u201d Stein said. \u201cThe key science question we want to answer is: How common are wandering black holes?\u201d<\/p>\n The answer may soon be within reach. \u201cPointed science observations with Swift’s UVOT and XRT (X-Ray Telescope) instruments are temporarily suspended as the mission awaits an orbit boost<\/a>, which is planned for this summer<\/a>,\u201d said co-author S. Bradley Cenko, Swift\u2019s principal investigator at NASA Goddard. The spacecraft, whose primary mission ran from 2004 to 2006, is slowly sinking toward Earth due to atmospheric drag after more than 20 years of observations of the changing universe. Nudging it to a higher orbit could extend its lifetime even longer. \u201cOnce it resumes normal operations, Swift could continue searching for more examples of out-of-place black holes.\u201d<\/p>\n In the coming years, scientists will use the new technique to search for disintegrating stars in observations from the newly operational Vera C. Rubin Observatory, jointly funded by the U.S. Department of Energy and National Science Foundation, in Chile and NASA\u2019s upcoming Nancy Grace Roman Space Telescope<\/a>.<\/p>\n \u201cRubin\u2019s wide, deep surveys will reveal a much larger sample of tidal disruption events than current observatories are capable of collecting, including ones that are off-center,\u201d Carney said. \u201cAnd Roman\u2019s space-based surveys will extend the current search zone by seeing ones that are farther away, looking back through 9 billion years of cosmic history.\u201d Adding their observations to Swift\u2019s and those from ground-based observatories will bring astronomers closer than ever before to completing a census of the universe\u2019s behemoth black holes.<\/p>\n To learn more about the Swift mission, visit:<\/p>\n https:\/\/nasa.gov\/swift<\/strong><\/a><\/p>\n By Ashley Balzer<\/strong> Media contact:<\/strong><\/p>\n Claire Andreoli<\/a>
NASA\u2019s Goddard Space Flight Center<\/strong><\/a>, Greenbelt, Md.<\/strong><\/p>\n
NASA\u2019s Goddard Space Flight Center<\/a>, Greenbelt, Md.
301-286-1940<\/strong><\/strong><\/p>\n<\/div>\n