Black holes are gatherers, not hunters. They lie in wait until an unlucky star passes by. When the star gets close enough, the black hole’s gravitational pull violently tears it apart and carelessly devours its gas while belching intense radiation.
Astronomers using NASA’s Hubble Space Telescope have recorded a star’s final moments in detail as it is swallowed by a black hole.
These are called “tidal disruption events”. But the wording belies the complex and raw violence of a black hole encounter. There is a balance between the black hole’s gravity pulling star stuff and the radiation removing the material. In other words, black holes are messy eaters. Astronomers are using Hubble to learn the details of what happens when a wayward star plunges into the gravitational abyss.
Hubble can’t photograph the chaos of the AT2022dsb tidal event up close because the injured star is nearly 300 million light-years away in the core of the galaxy ESO 583-G004. But astronomers used Hubble’s powerful ultraviolet sensitivity to study the light from the shredded star, which includes hydrogen, carbon and more. Spectroscopy offers forensic clues to black hole homicide.
About 100 tidal disruption events around black holes have been detected by astronomers using various telescopes. NASA recently reported that several of its high-energy space observatories observed another black hole tidal disruption event on March 1, 2021, and it happened in a different galaxy. Unlike the Hubble observations, the data were collected in X-ray light from an extremely hot corona around the black hole that formed after the star had already broken apart.
“However, there are still very few tidal events that are observed in ultraviolet light given the observation time. This is really unfortunate because there is a lot of information you can get from ultraviolet spectra,” he said. said Emily Engelthaler of the Center for Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Massachusetts. “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.” Changes in the state of the doomed star occur on the order of days or months.
For any given galaxy with a quiescent supermassive black hole at its center, stellar destruction is estimated to occur only a few times every 100,000 years.
This stellar snack event AT2022dsb was first captured on March 1, 2022 by the All-Sky Automated Survey for Supernovae (ASAS-SN or “Assassin”), a network of ground-based telescopes that survey the extragalactic sky about once a week for violent . , variable and transient events that shape our universe. This energetic collision was close enough to Earth and bright enough for Hubble astronomers to take ultraviolet spectroscopy over a longer-than-normal time period.
“These events are usually hard to spot. You can get some observations at the start of the disturbance when it’s really bright. Our program is different in that it is designed to look at a few tidal events over the course of a year to see what happens,” said CfA’s Peter Maksym. “We saw this early enough that we could see it in these very intense stages of black hole accretion. We saw that the accumulation rate decreased as it turned into a filter over time.”
The Hubble spectroscopic data are interpreted as coming from a very bright, hot, doughnut-shaped region of gas that was once the star. This area, known as the torus, is the size of the solar system and revolves around a black hole in the middle.
“We’re looking somewhere around the edge of that doughnut. We see a surface-sweeping stellar wind from the black hole that is projected toward us at speeds of 20 million miles per hour (three percent of the speed of light). ” Maksym said. “We’re still thinking about the event. You’ve shattered the star, and then you have this material that’s making its way into the black hole. And so you have patterns where you think you know what’s going on, and then you have what you actually see. This is an exciting place for scientists: right at the interface between the known and the unknown.”
The results were reported at the 241st meeting of the American Astronomical Society in Seattle, Washington.
Provided by NASA’s Goddard Space Flight Center
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