A supermassive black hole far from the center of its galaxy has been spotted after shredding a star. This observation provides direct evidence for a population of objects long hypothesized but difficult to detect. The phenomenon appeared as a sudden burst of light and X-rays.
The event, named AT2024tvd, corresponds to a tidal disruption event. A star wandered too close to the black hole, and gravitational forces stretched and tore it apart. Some of its matter formed a very hot disk, visible from Earth.
This illustration depicts a tidal disruption event, a phenomenon that occurs when a star passes dangerously close to a supermassive black hole. The shreds of the infalling star heat up as they swirl around the black hole, creating a glow visible from the far reaches of the cosmos, while the black hole ejects a relativistic jet into space.
Image NRAO/AUI/NSF/NASA
The unusual feature of the signal is its location. The black hole sits far from the bright core of its host galaxy, whereas known supermassive black holes generally occupy the central regions. This unusual location was confirmed by several observatories, including NASA's Swift satellite.
Researchers estimate the object has about one million solar masses. It may not be the supermassive black hole of the observed galaxy, but rather that of a small galaxy that was absorbed. During this merger, the stars of the satellite galaxy would have been scattered, leaving its black hole drifting in the galactic halo.
Wandering black holes are difficult to catalog because they emit almost nothing when they are not absorbing matter. The occasional destruction of a star then acts as a temporary signal. These flares make it possible to identify otherwise invisible objects and estimate their mass.
The galaxy WISEA J014656.04-152214.7, located about 750 million light-years away in the constellation Cetus, before and after a tidal disruption event was spotted on its outer edge in November 2025.
The left image was taken by the DESI (Dark Energy Spectroscopic Instrument) Legacy Survey and the right image comes from the Lowell Discovery Telescope.
Image Lowell Discovery Telescope / Legacy Survey / Robert Stein
This discovery could improve models describing galaxy growth. Simulations predict that a large number of off-center black holes remain after successive mergers. Their real abundance, however, remains poorly known, especially in distant or faint galaxies.
The future Vera C. Rubin Observatory should detect more similar events through its regular sky surveys. The Nancy Grace Roman Space Telescope will then be able to search for more distant cases. These instruments could turn these isolated detections into a true cosmic census.