São Paulo, SP (UOL/FOLHAPRESS) – A supermassive black hole “vomited” after swallowing a star that was very close three years ago. The “indigestion” occurred in long space 665 million light-years from Earth, and aroused the interest of astronomers around the world.
It is not uncommon for black holes to eject stellar matter into space. But three years is a long time for that. Usually, the process occurs immediately after the star is swallowed.
Details of the unprecedented observation were presented this week in a survey in The Astrophysical Journal.
The story began in June 2021, when a radio telescope in New Mexico detected signs that a black hole at the center of a galaxy had begun spewing material into space — and had not “eat” anything since 2018.
“We were totally surprised, no one had seen anything like this before,” Yvette Sendez, a research assistant at the Harvard-Smithsonian Center for Astrophysics and lead author of the study, said in an official statement.
The event was followed by a team of astronomers from six telescopes: four spread across North America, South America, Africa and Australia and two in space. The radio data collected was named AT2018hyz.
The black hole held stellar material for years, before ejecting it at an unusual speed – about 150 thousand kilometers per second (50% of the speed of light). The outflow for most tidal turbulence events is about 10% of the speed of light.
“It’s as if this black hole has suddenly started expelling a lot of material from the star that ate it up years ago,” Seendez explained.
This astronomical phenomenon is called a “tidal disturbance event” (or TDE): when a star passes very close to a black hole, it splits, or “cracks.” Stellar matter, like this, begins to spin around the black hole’s disk, instead of being immediately sucked up.
When the ejected material is heated during the process, it creates signals that can be detected from the ground. Tidal turbulence events are sometimes rapid, but stars can collapse slowly.
The team believes what happened to AT2018hyz may be more common than previously thought. To better understand, astronomers will need to look at more TDE — even the old, which seemed to be done, in case the material is ejected again.
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