Stars that come too close to a black hole are ripped apart by the black hole’s incredible tidal forces. These are called “tidal disturbances”.
Astronomers using NASA’s Hubble Space Telescope have captured in detail a star’s last moments as it is swallowed by a black hole. The event is called AT2022dsb tidal event.
Since the devoured star is at the center of the galaxy, ESO 583-G004, about 300 million light-years away, Hubble is unable to capture the chaos of the AT2022dsb tidal event up close. However, astronomers studied the fragmented star’s light, including hydrogen, carbon and more, using Hubble’s powerful ultraviolet sensitivity. The spectroscopy provides forensic clues to the black hole murder.
Emily Engelthaler of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Massachusetts, said: “However, very few tidal events have still been observed in ultraviolet light, given the observation time. This is a shame because there is a lot of information you can get from the ultraviolet spectra. We are excited because we can get these details about what the debris is about doing it. The tidal event can tell us a lot about a black hole.”
The stellar fragmentation is believed to occur only a few times every 100,000 years for a given galaxy with a silent supermassive black hole at its center.
The All-Sky Automated Survey for Supernovae (ASAS-SN or “Assassin”), a network of ground-based telescopes that scan the extragalactic sky about once a week for violent, variable, and transient events shaping our universe, was launched for the first time. first discovered this AT2022dsb stellar snacking event on March 1, 2022. Because of how close and bright this intense collision to Earth was, Hubble astronomers were able to conduct ultraviolet spectroscopy for longer than usual.
Peter Maksym of the CfA said: “Usually these events are difficult to observe. You get a few observations at the start of the disturbance when it is clear. Our program is different because it’s 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 into a trickle over time.
According to the Hubble spectroscopic data, the former star is now believed to have left a very brilliant, hot, doughnut-shaped region of gas. This region, called a torus, has a black hole at its center and is the size of the solar system.
Maksim said, “We’re looking somewhere on the edge of that donut. We see a stellar wind rushing out of the black hole across the projected surface at 20 million miles per hour (three percent of the speed of light).”
“We are still working on the event. You shred the star and then this material finds its way into the black hole. And so you have models that you think you know what’s going on, and then you have what you see. This is an exciting place for scientists: right at the intersection of the known and the unknown.”
The results were reported at a press conference Jan. 12 at the 241st meeting of the American Astronomical Society in Seattle, Washington.