• A wandering supermassive black hole, weighing one million solar masses, was discovered 600 million light-years away due to the tidal disruption event (TDE) AT2024tvd.
• This is the first time an offset TDE has been identified, suggesting the existence of a population of wandering black holes previously not well-studied.
• The discovery utilized NASA's Hubble Space Telescope, Chandra X-Ray Observatory, and NRAO's Very Large Array, revealing that the black hole is offset from the center of its host galaxy, which already contains a central supermassive black hole.

Astronomers have detected a wandering supermassive black hole located 600 million light-years away. This discovery was made possible by observing a tidal disruption event (TDE) called AT2024tvd, which occurs when a star gets too close to a black hole and is torn apart by its immense gravitational forces. Unlike most supermassive black holes that reside at the centers of galaxies, this one is found to be offset from the galactic center. The event emitted a burst of radiation detectable by telescopes, allowing scientists to pinpoint the black hole's location and study its behavior. This finding provides new insights into the dynamics and potential origins of black holes within galaxies.

• What: Discovery of a wandering supermassive black hole through the observation of a tidal disruption event (TDE) where the black hole ripped apart and swallowed a star, resulting in a burst of radiation.
• Who: Yuhan Yao (University of California at Berkeley), Ryan Chornock (UC Berkeley and ZTF team), Erica Hammerstein (UC Berkeley), NASA's Hubble Space Telescope, Chandra X-Ray Observatory, NRAO's Very Large Array, Zwicky Transient Facility (ZTF).
• When: The event occurred 600 million light-years ago, but the radiation burst was detected recently. The findings are to be published in the Astrophysical Journal Letters, with a preprint available from Feb 2025.
• Where: The event occurred in a galaxy 600 million light-years away. The wandering black hole is located within the bulge of the host galaxy but is offset from the center.

The discovery of an offset TDE and its associated wandering black hole challenges the conventional understanding of black hole locations within galaxies. The presence of a smaller, roaming black hole alongside a larger, central one raises questions about their origins and future interactions. The two main theories proposed for the offset black hole's location are ejection from the galactic center due to three-body interactions, and being the remnant of a smaller galaxy that merged with the host galaxy. This finding highlights the importance of TDEs as tools for identifying otherwise undetectable black holes and opens new avenues for research into the dynamics of galactic nuclei and the evolution of galaxies.

AT2024tvd is the first offset TDE captured by optical sky surveys, and it opens up the entire possibility of uncovering this elusive population of wandering black holes with future sky surveys.

Tidal disruption events hold great promise for illuminating the presence of massive black holes that we would otherwise not be able to detect.

If the black hole went through a triple interaction with two other black holes in the galaxy’s core, it can still remain bound to the galaxy, orbiting around the central region.

The discovery of the wandering black hole through the AT2024tvd event signifies a major leap in understanding black hole behavior and galactic dynamics, providing strong evidence for a population of black holes existing outside of galactic centers. This discovery, made possible through the combined power of telescopes like Hubble and Chandra, offers insights into several key areas. The black hole, with a mass of approximately one million Suns, is located about 2,600 light-years from the host galaxy's center, which harbors a supermassive black hole of 100 million solar masses. The origin of this wandering black hole is still uncertain, with two primary hypotheses: it could be the result of a galaxy merger, where it was once the central black hole of a smaller galaxy, or it could have been ejected from the galactic center through three-body interactions with other black holes. Continued monitoring and theoretical modeling are crucial to understanding its origin and ultimate fate. Future observations, potentially with the James Webb Space Telescope, could provide deeper constraints and help determine if the black hole retains a stellar counterpart. The AT2024tvd event, the first offset tidal disruption event (TDE) identified by optical sky surveys, highlights the importance of considering offset TDEs in theoretical models. This discovery is expected to motivate further research into the rates and characteristics of these events. Discovering more wandering TDEs will give astronomers a better idea of how frequently galaxies and their central black holes merge, which will help us understand how supermassive black holes form. Furthermore, the discovery validates plans for future space missions like LISA, which will search for gravitational waves produced by merging massive black holes. Future sky surveys are expected to uncover more of these elusive wandering black holes.