This month has been an astronomical buffet — from astronomers realising we might have the tools to deter dangerous asteroids to theorising the unprecedented rapid origins of our lunar satellite. And as we come fresh off the heels of such extremely intriguing events, we are immediately greeted with an exciting and inexplicable burp from one of the heftiest kings of the cosmic universe: a black hole.
Bear with us; this isn’t as disgusting as it sounds. Black holes are known for their unquenchable hunger and can put any competitive eater to shame. But everyone reaches their limits eventually, even these cosmic behemoths. So every once in a while, black holes tend to pause mid-feast to burp out some of the cosmic stardust they have already gorged on.
But this time, there is something very weird about this black hole; it has begun spewing out material, that too completely unprompted and after three years!
In October 2018, the black hole in question, which is located about 665 million light years away from us, ripped a small star to shreds. This event was dubbed the AT2018hyz, and its story was quickly written off when the final remnants of light from the initial star faded away in 2018. This is fairly common and known as a tidal disruption event (TDE), so scientists weren’t too perturbed by it.
However, after three years of inactivity, the black hole started burping out spaghettified bits of mass from its core, and scientists have no idea why.
“This caught us completely by surprise — no one has ever seen anything like this before,” says Yvette Cendes, a research associate at the Harvard & Smithsonian Center for Astrophysics.
What’s even weirder is that this was no ordinary burp, as this whiff has been odorising the expanses of space at half the speed of light since June 2021!
“We have been studying TDEs with radio telescopes for more than a decade, and we sometimes find they shine in radio waves as they spew out material while the star is first being consumed by the black hole,” says Edo Berger from Harvard University.
“But in AT2018hyz there was radio silence for the first three years, and now it’s dramatically lit up to become one of the most radio-luminous TDEs ever observed.”
Black holes are known to be messy eaters, and they sometimes release “spaghettified” morsels of their meals into space mid-gorge. But these outflows are usually observed right after the black hole feasts, not after three years and certainly not at half the speed of light! So, why was this burp so aggressive?
“This is the first time that we have witnessed such a long delay between the feeding and the outflow,” Berger says. “The next step is to explore whether this actually happens more regularly and we have simply not been looking at TDEs late enough in their evolution.”
The findings of this study were published in The Astrophysical Journal and can be accessed here.
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