Illustration of the star brightening when it enters the black hole. Credit: Courtesy of Carnegie Institution for Science
When you wish upon a star, you might get to watch a black hole shred it.
Astronomers from Ohio State and Carnegie Observatories in Pasadena, California, were able to get a comprehensive look at a black hole shredding a star by using a network of robotic telescopes called All-Sky Automated Survey for Supernovae that are located around the world, along with NASA’s Transiting Exoplanet Survey Satellite, Patrick Vallely, a co-author of the study and National Science Foundation graduate research fellow at Ohio State, said.
“When a star gets too close to a black hole while moving at the right speeds, it can get torn apart,” Vallely said. “When the star is in the black hole, it’s interacting, heating up, and as a result it gets really bright, which is what we saw with this.”
Gravity from the black hole is so strong that it pulls much harder on the front end of the star compared with the back, which forms a long stream of light as it tears apart — creating a tidal disruption event, Tom Holoien, a Carnegie Observatories fellow and Ohio State alumnus, said.
“It was about 375 million light-years away from Earth,” Holoien said. “That means this happened 375 million years ago, and the light just reached us in January.”
Holoien said the black hole was 6 million times the mass of the sun.
He said he received an alert when the shredding was first detected through data in South Africa, allowing him to turn the telescopes and gather information within a day of the discovery. He witnessed the event Jan. 29 at a Carnegie observatory located in Chile.
“We didn’t really get any advanced warning it was happening,” Vallely said. “We got an email about it brightening and knew to immediately get on it.”
Vallely said that after telling the telescopes where to point, they will start obtaining the data.
Holoien said this has happened before, but what was unique this time was that this part of the sky was being monitored already.
“The beginning of it getting brighter has never been seen before,” Holoien said. “We also found this early in our data as well, so we were able to trigger a lot of follow-up data with other telescopes earlier than we have before.”
Holoien said these events depend on different properties, and the brighter the star, the larger the black hole probably is. Measuring how long the star takes to get brighter can tell researchers what size the black hole is and how it’s evolving.
This occurs once every 10,000 to 100,000 years, making it rare to other things we see in the universe, Holoien said.
“All the puzzle pieces fall together to make it one of the best observed tidal disruptions yet,” Vallely said.
