Black holes keep ‘burping’ stars they destroyed years ago, and astronomers don’t know why

Astronomers made this discovery after years of observing black holes associated with tidal disturbance events (TDEs). TDE occurs when stars get too close to a black hole. The immense gravity of these cosmic monsters creates an amazing tidal force that stretches and compresses the stars – a process known as spaghettiization. The unfortunate stars associated with TDE are ripped apart or “debunked” within hours, signaled by a strong flash of electromagnetic radiation in visible light. Some of the destroyed star’s stellar matter is ejected from the black hole while the rest forms a thin, plastic disk-like structure around it called an accretion disk, which gradually pushes the material into the hole. black. In the early stages, the accretion disk is unstable and the material moves and hits itself, causing outflows that can be detected by radio waves. But traditionally, astronomers have only observed these star-eating black holes for a few months after TDE. Related: A ‘killer’ black hole tore apart a star and left its interior scattered across the galaxy.

In the new study, however, astronomers observed TDE-related black holes for hundreds of days and found that in up to 50% of cases, the black holes “reflect” much stellar matter. next year TDE. Lead author of the study, Yvette Cendes, said: “If you look back many years, a very large portion of black holes that did not emit radio emissions in those early days would suddenly glow as radio waves. “. research associate at,” the Harvard and Smithsonian Center for Astrophysics told Live Science. “I call it ‘burp’ because we have a kind of lag where this material doesn’t come out of the accretion disk until much later than people would expect.” The replay of this material for 10 of the 24 black holes occurs two to six years after the events that destroy the star. The observations described in a study uploaded to the arXiv preprint database on August 25 have not been peer-reviewed. Black holes are definitely mess eaters. Cendes and team don’t know what causes the black hole to “light up” after so many years, but whatever it is, it certainly doesn’t come from within the black hole. Black holes are marked by an event horizon, the point at which gravity is so strong that not even light can escape. “A black hole is a very intense gravitational environment before you cross that event horizon, and that’s what really drives it,” Cendes said. . “We really don’t understand whether the matter seen in the radio waves originates from the accretion disk or is stored somewhere closer to the black hole. However, black holes are definitely omnivores.”

Part of the mystery comes from computer simulations of TDE, which usually ends just weeks after the star is destroyed. New research suggests that models need to be updated to capture some of the more unexpected behavior of black holes. For example, in two cases, the radio waves emitted by the black hole peak, then decrease, and then peak again. “Having the second peak, the two black holes are illuminated again, that’s completely new and unexpected,” Cendes said. “People thought there was going to be a way out, and then it happened. This observation therefore means that these black holes can “burn up” and then “burn up” again. Cendes said the team will continue to monitor any black holes that cause TDEs, particularly as some of them continue to get brighter.