It happened years after swallowing the stars. There are 24 black holes that suddenly exploded. They emitted radio waves in unexplained episodes that resemble a ‘burp’. It is estimated that half of the black holes burp stars. Why? The discovery was made after years of observation.
It occurs with black holes involved in tidal disruption events (TDEs). TDEs occur when stars venture too close to black holes. The immense gravity of these cosmic monsters exerts incredible tidal forces. They stretch and squeeze the stars, a process called spaghettification. Stars involved in EDTs are shattered or disentangled in a matter of hours.
Some of the stellar material from the destroyed star is thrown away from the black hole. The rest forms a thin flying disk-like structure around it called an accretion disk. It gradually feeds the black hole. In its early days, the accretion disk is unstable, and matter sloshes and crashes into itself. But a long investigation found that they do so again years later.
“Years later, the black holes become will ignite suddenly on the radio waves.” Yvette Cendes of the Harvard Smithsonian Center for Astrophysics explained,
“Black holes are very extreme gravitational environments. Even before you get past that event horizon. And that’s what’s really driving this,” he said. They don’t yet know whether the material observed in the radio waves is coming from the accretion disk or from somewhere closer to the black holes.
Turned on again
Part of the mystery comes from the computer models that simulate EDTs. They usually terminate a few weeks after the star’s destruction. The models must be updated to capture some of the more unexpected behavior of black holes. In two cases, radio waves peaked twice.
“There was a second peak, the two black holes re-lit. And that’s completely new and unexpected,” Cendes detailed. He concluded that this observation means that these black holes can turn on and then do it again. Black holes burp stars after many years. Because of them, the team will continue to monitor all those that cause EDTs. Especially since some of them are getting even brighter.