Astronomers have detected a supermassive black hole tearing apart a star in the outskirts of a galaxy about 750 million light-years from Earth. The flare produced by the event offers one of the strongest pieces of evidence yet that supermassive black holes can drift away from the centers of their galaxies.
The flare, cataloged as tidal disruption event TDE 2025abcr, was spotted in the constellation Cetus. It revealed a black hole estimated at roughly one million solar masses sitting in the outer reaches of its host galaxy, far from the galactic nucleus.
Tidal disruption events occur when a star passes close enough to a black hole for the difference in gravitational attraction across the star to tear it apart. Some of the stellar debris is ejected into space, while the rest forms a hot disk around the black hole and produces a bright glow at optical, ultraviolet and X-ray wavelengths. The glow is visible for a limited time, and while it lasts it makes visible black holes that would otherwise remain inactive and undetectable.
TDE 2025abcr was first detected in October 2025 by the Zwicky Transient Facility, which monitors the northern sky from Palomar Observatory in California. The detection algorithm was built to identify an extremely rare signal among a huge number of false candidates. Each night the facility records roughly half a million brightness variations, most of them caused by supernovae, variable stars and active galactic nuclei. Tidal disruption events account for only about 0.5 percent of the transients seen in this type of survey, and nearly all previous searches concentrated on galactic centers.
The new event stands out because of where it happened: about 9.3 kiloparsecs from the center of its host galaxy, a distance equivalent to more than 30,000 light-years. According to the study, no tidal disruption event had ever before been observed so far from a galaxy's core. The host galaxy, listed as WiseA J014656.04-152214.7, lies in the constellation Cetus.
To characterize the flare, the team used ground-based telescopes and NASA's Neil Gehrels Swift Observatory, which recorded a strong ultraviolet signal and soft X-ray emission, both matching expectations for a tidal disruption event. The properties of the light curve are not especially unusual compared with other optically detected events; what makes this one exceptional is its location. From the peak brightness, the researchers estimated that the black hole has a mass on the order of one million solar masses, while the supermassive black hole at the center of the host galaxy is thought to be hundreds of times more massive.
The discovery also validates a new way of finding such objects. «We were looking for tidal disruption events of this type to identify supermassive black holes that are otherwise invisible and are moving away from the galactic nuclei where they usually reside,» said Robert Stein, a researcher at the University of Maryland and NASA's Goddard Space Flight Center and lead author of the study. «With this discovery, one of the few confirmed so far, we were also able to validate a new technique that we can use to find other similar events.»
Astronomers have proposed two main explanations for how a black hole ends up in a galaxy's outer reaches. In one scenario, three or more galaxies merged and the gravitational tug-of-war between their central supermassive black holes flung the lightest one out toward the galaxy's edge. In another, a dwarf galaxy caught in a merger lost its stars to a larger galaxy, and one of those stars passed too close to the dwarf galaxy's supermassive black hole.
Stein said further discoveries could clarify how common such objects are. «Further discoveries could reveal the origin of this apparent orphan black hole,» he said. «The fundamental scientific question we want to answer is: How common are wandering black holes?»
The findings were published in The Astrophysical Journal Letters.
