Supermassive black holes that shred stars produce delayed radio emissions years after the initial tidal disruption event, astronomers discovered using the Very Large Array radio observatory.
When a star wanders too close to a black hole, gravitational forces tear it apart in what researchers call a tidal disruption event (TDE). The initial explosion releases enormous energy as material falls toward the black hole. But the action doesn't end there.
Observations with the NSF-funded Very Large Array revealed that many of these black holes eject powerful streams of material long after the initial outburst. These jets collide with surrounding gas clouds and produce radio emissions years later, creating what researchers describe as "burps" of radiation.
The discovery matters for understanding how supermassive black holes grow and influence their host galaxies. When black holes accrete material and launch jets, they inject energy back into galaxies in a process called feedback. This feedback regulates star formation and shapes galaxy evolution.
The Very Large Array's sensitivity allowed astronomers to detect these delayed radio emissions that would escape less powerful instruments. The radio bursts occur as the ejected material expands outward and strikes the gas surrounding the black hole, heating it and causing it to glow at radio frequencies.
The timing of these "burps" varies significantly among different events. Some black holes emit detectable radio signals within months, while others wait years before launching their jets. This delay suggests variable accretion processes around black holes following tidal disruption.
The findings provide astronomers with a more complete picture of tidal disruption events. Rather than discrete violent episodes, these events produce ongoing effects that persist long after the initial star destruction. Future observations with the Very Large Array and other radio facilities will help map out the timescales and energetics of post-TDE jet activity, potentially revealing new details about how black holes consume material and redistribute energy throughout their galax