A black hole ‘burps’ digested material for three years

Oct. 13 () –

In October 2018, a star shattered when it got too close to a black hole in a galaxy located 665 million light years from Earth.

But almost three years after the massacre, the same black hole lights up the skies again and nothing new has been swallowedsay the scientists. “This took us completely by surprise: no one had ever seen anything like this before,” he says. it’s a statement Yvette Cendes, associate researcher at the Center for Astrophysics | Harvard & Smithsonian (CfA) and lead author of a new study looking at the phenomenon.

The team concludes that the black hole is now ejecting material traveling at half the speed of light, but they are not sure why the exit was delayed by several years. The results, described in The Astrophysical Journalmay help scientists better understand the feeding behavior of black holes, which Cendes compare to “burping” after a meal.

The team detected the unusual outburst while reviewing tidal disruption events (TDEs), when invading stars are spaghetti-slapped by black holes, that have occurred in recent years.

Radio data from the Very Large Array (VLA) in New Mexico showed that the black hole had mysteriously reanimated in June 2021. Cendes and the team rushed to examine the event more closely.

The team collected observations of the TDE, dubbed AT2018hyz, in multiple wavelengths of light using the VLA, the ALMA Observatory in Chile, MeerKAT in South Africa, the Australian Telescope Compact Array in Australia, the Chandra X-ray Observatory, and the Swift Observatory in Australia. space. The TDE radio observations turned out to be the most striking.

“We’ve been studying TDEs with radio telescopes for more than a decade, and sometimes we find that they glow in radio waves as they shed material as the black hole first consumes the star,” says Edo Berger, professor of astronomy at Harvard. and CfA, and co-author of the new study. “But on AT2018hyz there was radio silence for the first three years, and has now brightened dramatically to become one of the most luminous radio TDEs ever observed.”

TDEs are well known for emitting light when they occur. As a star approaches a black hole, gravitational forces begin to stretch or stretch the star. Eventually, the elongated material spirals around the black hole and heats up, creating a flash that astronomers can detect from millions of light-years away.

Occasionally some spaghetti material is blasted back into space. Astronomers compare it to mess-eating black holes: not everything they try to consume makes it to their mouths.

But the emission, known as the outflow, typically develops quickly after a TDE occurs, not years later. “It’s as if this black hole has abruptly started belching out a bunch of material from the star that it ate years ago,” Cendes explains.

In this case, the burps are resounding. The flow of material travels at a speed of 50% of the speed of light. For comparison, most TDEs have an outflow that travels at 10% the speed of light, Cendes says.

“This is the first time we’ve witnessed such a long delay between feeding and output,” says Berger. “The next step is to explore whether this really it happens more often and we just haven’t been looking at TDEs late enough in their evolution.”