Stars that wander too close to a black hole are ripped apart by the incredible tidal forces of the black hole. These are termed “tidal disruption events.”
Astronomers using NASA’s Hubble Space Telescope have recorded a star’s final moments in detail as it gets gobbled up by a black hole. The event is dubbed as AT2022dsb tidal event.
Since the devoured star is located at the galaxy’s center, ESO 583-G004, about 300 million light-years away, Hubble cannot capture the mayhem of the AT2022dsb tidal event up close. However, astronomers studied the light from the fragmented star, which includes hydrogen, carbon, and more, using Hubble’s powerful ultraviolet sensitivity. The spectroscopy provides forensic clues to the black hole homicide.
Emily Engelthaler of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Massachusetts, said, “However, there are still very few tidal events observed in ultraviolet light given the observing time. This is unfortunate because there’s a lot of information that you can get from the ultraviolet spectra. We’re excited because we can get these details about what the debris is doing. The tidal event can tell us a lot about a black hole.”
The stellar shredding is thought to occur just a few times every 100,000 years for any given galaxy with a quiescent supermassive black hole at its center.
The All-Sky Automated Survey for Supernovae (ASAS-SN or “Assassin”), a network of ground-based telescopes that scans the extragalactic sky roughly once a week for violent, variable, and transient events that are shaping our universe, first discovered this AT2022dsb stellar snacking event on March 1, 2022. Because of how close and bright this intense collision was to Earth, Hubble astronomers could conduct ultraviolet spectroscopy for longer than usual.
Peter Maksym of the CfA said, “Typically, these events are hard to observe. You get a few observations at the beginning of the disruption when it’s bright. Our program is different because it is designed to look at a few tidal events over a year to see what happens. We saw this early enough to observe these intense black hole accretion stages. We saw the accretion rate drop as it turned to a trickle over time.”
According to the Hubble spectroscopic data, the former star is now believed to have left behind a highly brilliant, hot, donut-shaped gas region. This region, called a torus, has a black hole in the center and is the size of the solar system.
Maksym said, “We’re looking somewhere on the edge of that donut. We’re seeing a stellar wind from the black hole sweeping over the surface projected towards us at 20 million miles per hour (three percent the speed of light).”
“We are still getting our heads around the event. You shred the star, and then it’s got this material making its way into the black hole. And so you’ve got models where you think you know what is going on, and then you’ve got what you see. This is an exciting place for scientists: right at the interface of the known and the unknown.”
The results were reported during a press conference on January 12 at the 241st meeting of the American Astronomical Society in Seattle, Washington.