Three years after a black hole shredded and devoured a small star, it's lighting up the night sky with violent emissions as it burps out material from its messy meal.
A star was torn up by a black hole in October of last year. Astronomers observe violent encounters between stars and black holes a lot. When objects such as stars approach black holes, they generate tidal forces that stretch the star in one direction while squashing it in the other, which is called a tidal disruption event.
Astronomers can see a flash of light from millions of light years away when spaghettified material falls onto a black hole. The black hole can sometimes spit out some of the stellar material. Black hole are messy eaters.
Black holes turn stars into spaghetti.
Despite not having eaten anything since this small star, the black hole is still releasing material from its last meal.
"No one has ever seen anything like this before, and this caught us completely by surprise," said the astronomer who led the research. It's as if the black hole is burping out material from the star it ate a long time ago.
The material is being ejected from the black hole at a slower rate than light. TDEs spit out about 10% of the light's speed of light.
It's a mystery why it took so long for this black hole to burp out its final meal.
Edo Berger, an astronomy professor at Harvard University, said in the statement that this was the first time they had seen such a long delay between the feeding and the outflow.
As they were looking for signs of TDEs, the astronomer spotted this event. The black hole burst back to life in June of 2021. They were encouraged by this finding to look further.
Director's Discretionary Time is when you find something so unexpected that you can't wait for the normal cycle of telescope proposals to see it. The applications were accepted.
The team studied the event in multiple wavelength of light and found that the most striking observations were made in radio.
"We have been studying TDEs with radio telescopes for more than a decade, and we sometimes find they shine in radio waves as they emit material while the star is first being eaten by the black hole," Berger said. There was no radio for the first three years, but now it is one of the most radio-luminous TDEs ever observed.
Sebastian Gomez, a fellow at the Space Telescope Science Institute in Baltimore, is a co-author of the study. He thought this TDE was unremarkable.
In the statement, Gomez said that they set it out of their minds after watching it in visible light for a while.
If the delay between feeding and emitting is unique to AT18hyz, the team will look into it.
We have not been looking at TDEs late enough in their evolution and the next step is to explore if this actually happens more frequently.
The work was published in a journal.
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