DESY, Scientific Communication Laboratory
Astronomers have published a major discovery: A black hole ‘ejected’ energy from a small star it was observed shredding in 2018, after two years of not ejecting any material from it. this guy.
How unusual is that?
“Super unusual”, Yvette Cendes, astronomer at the Center for Astrophysics, Harvard and Smithsonian and lead author paper, tells NPR. “We’ve never really seen this before to this degree.”
The researchers made the discovery when they used a powerful radio telescope facility – the Very Large Array in New Mexico – to check some two dozen black holes where stars had been shredded after getting too close to them. That is, the star material has been separated or “spaghettified”. Such events are called tidal disturbance events, or TDEs.
What they discovered was that one of the TDEs (the one named AT2018hyz, if you’re curious) was emitting energy at an unusual rate and at a very surprising time: more than two years after the event. .
This behavior is different from what has been observed in black holes before, in two ways. First, timing: It’s most common to see radio emissions from black holes in the first few months after swallowing a star. And second, the energy emitted in this case doesn’t quite match what astronomers have seen before.
In most cases of black holes swallowing stars, perhaps 99%, the outflow is lower in energy. And in 1% of cases, this flow is much larger – “an extremely violent event”, says Cendes, a very rare event.
But in this case? It’s in between – about half the speed of light.
This marks “the first instance where we’ve seen this kind of speed associated with this event or this type of output,” Cendes says. “But also that it happened – the best guess we have is about two years after the star was eaten by this black hole, that’s when this outing started – and that’s really exciting. . This has never been seen before.”
And scientists don’t know why this happens.
Cendes says that although the research team did a good job of ruling out this is not cause they don’t have an answer yet for what is.
You might be wondering: Hey, I thought nothing could escape from a black hole?
“There’s a point when you get too close to a black hole that you can’t escape the black hole anymore – that’s called the event horizon. But this material never crossed that border, according to our best estimates”, explains Cendes.
In other words, the star has come close enough to the black hole to be shredded — but not to fall into that point of no return.
The team’s discovery means exciting new avenues of research.
“For the theorists, it’s really exciting because suddenly it really opens up a whole new dimension in our understanding of physics and what’s possible. … They absolutely have to get to work and tell me what’s going on. happens because I’m also very curious,” laughs Cendes.
And, she says, there are other star-eating black holes to study in more depth. It could be that events like this are more common than astronomers previously thought.
For Cendes, the discovery is what she and her fellow astronomers hope to find – something big.
“I wanted to be an astronomer since I was 13,” she says. “Making this discovery was really the thrill of a lifetime for me. … It was really a lot of work and I certainly had a lot of great collaborators to help me get this out, but it was very , very rewarding and that’s what I wanted, so it’s been pretty awesome.