For the first time ever, NASA’s TESS managed to get an unprecedented view of a black hole shredding a star.
The transiting exoplanet survey satellite has caught one of the most detailed looks yet at the phenomenon, called a tidal disruption event (or TDE).
Tidal disruptions are incredibly rare and they happen when a star gets too close to a black hole.
“TESS data let us see exactly when this destructive event, named ASASSN-19bt, started to get brighter, which we’ve never been able to do before,” said Thomas Holoien, a Carnegie Fellow at the Carnegie Observatories in Pasadena, Calif., in a statement.
However, this milestone wouldn’t be possible without the help of the ASAS-SN (All-Sky Automated Survey for Supernovae). That’s a worldwide network of robotic telescopes, with the headquarter at The Ohio State University.
“We’ve been closely monitoring the regions of the sky where TESS is observing with our ASAS-SN telescopes, but we were very lucky with this event in that the patch of the sky where TESS is continuously observing is small, and in that this happened to be one of the brightest TDEs we’ve seen,” said Patrick Vallely, a co-author of the study and National Science Foundation Graduate Research Fellow at Ohio State.
“Due to the quick ASAS-SN discovery and the incredible TESS data, we were able to see this TDE much earlier than we’ve seen others—it gives us some new insight into how TDEs form.”
The supermassive black hole that generated ASASSN-19bt lies at the center of a galaxy about 375 million light-years away. Astronomers think the black hole weighs around 6 million times the sun’s mass. Meanwhile, the destroyed star may have been similar in size to our sun.
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ASAS-SN was the first to discover the event. As it did, it sent out an alert to international astronomers, so that they could track it themselves.
Holoien received that alert and immediately trained two Las Campanas telescopes on the tidal disruption event. He then requested follow-up observations by other telescopes around the world.
Luckily, TESS was already monitoring the exact part of the sky where the ASAS-SN telescope saw the event.
Black Hole Shredding a Star
Tidal disruptions happen only once every 10,000 to 100,000 years in a galaxy the size of our Milky Way. And it’s very hard to observe these events.
To get chewed up, the star must pass by the black hole at a distance about as close as our Earth is to the sun.
“Imagine that you are standing on top of a skyscraper downtown, and you drop a marble off the top, and you are trying to get it to go down a hole in a manhole cover,” Ohio State astronomer Chris Kochanek said. “It’s harder than that.”
“We were very lucky with this event in that the patch of the sky where TESS is continuously observing is small, and in that this happened to be one of the brightest TDEs we’ve seen,” Vallely said.
Researchers published the study in the Astrophysical Journal.