Astronomers have discovered a monstrous black hole with an appetite for food and a sweet tooth. The black hole unwraps an ill-fated star, spreading it out like candy and shaping the “remains” into a stellar donut the size of the solar system, before feasting on this cosmic confection.
The Automated All-Sky Survey for Supernovae (ASAS-SN or “Assassin”) first observed the violent incident, called a Tidal Disruption Event (TDE), in a flash of high-energy radiation. The celebration takes place in the heart of a galaxy 300 million light years away.
Astronomers followed up the observations of the flash by surveying the scene at the center of the galaxy ESO 583-G004 in ultraviolet light using the Hubble Space Telescope. Although Hubble is too far from this TDE, designated AT2022dsb, to observe the star’s fate as it unfolded, the team of astronomers was able to recreate the scene using light from the doomed star.
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Spectra of the star revealed how it was torn apart by the black hole before it was stretched like a jackhammer and pulled into the black hole. The TDE process left the cosmic monster surrounded by a doughnut-shaped torus of stellar material and superheated gas, and while much of this material will gradually fall into the black hole, some will escape into space.
Black holes are messy eaters
So far, telescopes including Hubble have observed about 100 of these violent interactions between black holes and stars that come too close to them, triggering destruction by the tidal forces created by the black hole’s immense gravitational influence. What makes the observation of AT2022dsb special is that it was made in ultraviolet light, whereas most TDEs are observed in X-ray light.
“There are still very few tidal events that are observed in ultraviolet light given the observing time,” Harvard-Smithsonian Center for Astrophysics (CfA) researcher Emily Engelthaler said in a statement. (opens in a new tab). “That’s really unfortunate because there’s a lot of information you can get from ultraviolet spectra.”
The team that observed TDE AT2022dsb using ultraviolet spectroscopy was able to monitor it for a longer period than usual, from its inception to the later stages of ‘feeding’ or ‘accretion’.
“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 researcher 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.”
TDEs have shown astronomers that black holes are “messy eaters,” meaning that some of the material left over from the destruction of unlucky stars in these feeding events will be thrown into space, possibly as the jets of matter it moves at incredible speeds approaching that of light. .
This TDE is no different. The team’s observations reveal a stellar wind hurtling toward Earth at about 3 percent the speed of light, or about 20 million miles per hour (about 32.2 million kilometers per hour).
Changes in what’s left of the destroyed star in TDE AT2022dsb occur on a time scale of days to months, meaning ultraviolet spectroscopy and observations of these changes can tell astronomers more about what’s going on with the black hole.
“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,” Engelthaler added. “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.”
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Spotting the edge of a cosmic doughnut
Spectroscopic data from AT2022dsb collected by Hubble was analyzed by the team which believes it comes from a very bright, hot, doughnut-shaped region of gas that was once the star’s constituent material.
They were also able to determine that this torus of gas orbiting the black hole is the size of our solar system. Observations are taken from somewhere on the edge of the donut according to Maksym.
“We are still thinking about the event,” concluded Maksym. “You crush the star and then you have this material that makes 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 team’s findings were announced at the 241st meeting of the American Astronomical Society on Wednesday, January 12.
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