Black hole erupts previously engulfed star with scientists observing it first time ever

Anything that enters a black hole stays there forever – even light cannot leave it. That, at least, was the conventional wisdom. Now, however, scientists have for the first time seen a black hole spew out the remains of a star it swallowed years ago.

According to The Harward Gazette, in October 2018, a small star flew too close to a black star in a galaxy 665 million light-years away from Earth and was torn apart and consumed by it.

“This caught us completely by surprise – no one has ever seen anything like this before,” says Yvette Cendes, a research associate at the Center for Astrophysics | Harvard & Smithsonian (CfA) and lead author of a new study analyzing the phenomenon.

For astronomers, there was nothing unusual about this event: it happens all the time in space. But more than unexpected was the fact that the star recently spewed out some of the swallowed matter. Today, about three years after that star's absorption, a black hole again lights up the sky – and it hasn't absorbed anything new since then.

The team of scientists concluded that the black hole now ejects some of the absorbed matter at half the speed of light. However, scientists do not understand why this began to happen several years after the absorption of the star.

The scientists described their observations in the Astrophysical Journal. Perhaps the study of this phenomenon will help scientists better understand the behavior of black holes. For now, Sendes compares what happened with a "burping" after a meal.

Scientists noticed the unusual outburst when they revisited a tidal disruption event (TDE) that occurred several years ago, which is when a star approaches close enough to the event horizon of a supermassive black hole, and the tidal forces of the black hole tear it apart, "spaghettifying" it.

Radio data from the Very Large Array (VLA) in New Mexico showed that in June 2021, the black hole was mysteriously "reanimated. At that time, scientists began collecting data from several observatories around the world.

“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, professor of astronomy at Harvard University and the CfA, and co-author on the new study. “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.”

Scientists plan to study this phenomenon further. Something like this may happen quite often, it is just that no one has followed engulfing of start by black holes long enough to see it.