Scientists say a black hole has begun ejecting material years after it consumed a small star, a phenomenon described as similar to “burping” after a meal and a first for researchers.
A study published on Oct. 11 in The Astrophysical Journal suggests the black hole, in a galaxy 665 million lights years away from Earth, is shooting material at half the speed of light after ripping apart a star that wandered too close to it in October 2018.
The research team behind the study says it is unsure why this outflow was delayed by several years.
“This caught us completely by surprise — no one has ever seen anything like this before,” lead author Yvette Cendes, a research associate at the Center for Astrophysics, a collaboration between Harvard University and the Smithsonian, said in a news release.
Researchers observed the event while revisiting tidal disruption events (TDE), when encroaching stars are “spaghettified” by black holes.
Radio data from the Very Large Array of radio telescopes in New Mexico showed the black hole had reanimated in June 2021, they say.
As a star nears a black hole, gravitational forces stretch it out, the researchers say. The material then spirals around the black hole and heats up, creating a flash that astronomers can observe millions of light years away. Some material is occasionally flung into space.
But the scientists say this outflow normally happens quickly after a TDE, not years later.
“It’s as if this black hole has started abruptly burping out a bunch of material from the star it ate years ago,” Cendes said.
Even though the material is travelling at 50 per cent the speed of light, most TDEs have outflow that travels at 10 per cent of the speed of light, Cendes said.
The team says the results may help scientists better understand the feeding behaviour of black holes.
One question researchers hope to explore is whether this phenomenon happens more often than previously thought.