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 grip violently tears it apart and carelessly devours its gases while spitting out intense radiation.
Now astronomers using NASA’s Hubble Space Telescope have recorded in detail the final moments of a star as it is engulfed by a black hole.
Although encounters with black holes are violent, they’re known as ‘tidal disturbance events’ – and astronomers use Hubble to uncover the details of what happens when a wayward star plunges into the gravitational abyss.
“The AT2022dsb tidal event” cannot be photographed up close with Hubble because the chewed-up star is nearly 300 million light-years away. But astronomers have used Hubble’s ultraviolet sensitivity to study light from the shredded star, which includes hydrogen, carbon and more, all forensic clues to the black hole’s homicide.
About 100 tidal disturbance events around black holes have been detected by astronomers using various telescopes. NASA recently reported spotting another black hole tidal disturbance event March 1, 2021, from another galaxy.
The data was collected in X-ray light from an extremely hot corona around the black hole, after the star had already been torn apart.
“There’s a lot of information you can get from ultraviolet spectra,” said Emily Engelthaler of the Center for Astrophysics | Harvard & Smithsonian (CFA).
“We’re excited because we can get those details of what the debris is doing. The tidal event can tell us a lot about a black hole.
Changes in the doomed star’s state occur on the order of days or months, but for any given galaxy with a quiescent supermassive black hole at the center, NASA believes the loss only occurs a few times. every 100,000 years.
This AT2022dsb stellar nibbling event 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 surveys the extragalactic sky about once a week to detect violent, variable, and transient events that shape our universe. This energetic collision was close enough to Earth and bright enough for Hubble astronomers to perform ultraviolet spectroscopy over a longer than normal time period.
“Generally, these events are difficult to observe. You might get a few sightings early in the disturbance when it’s really bright. Our program is different in that it’s designed to look at a few tidal events over a year to see what’s going on,” said Pierre Maksym of the CFA. “We saw this early enough to be able to observe it in these very intense black hole accretion stages. We’ve seen the accretion rate drop as it drips over time.
Spectroscopic data from Hubble is interpreted as coming from a very bright, hot, doughnut-shaped area of gas that was once the star. This area, known as the torus, is the size of the solar system and swirls around a black hole in the middle.
“We’re looking somewhere on the edge of this donut. We see a stellar wind from the black hole sweeping across the surface that is hurled towards us at speeds of 20 million miles per hour (three percent of the speed of light),” Maksym said.
“We’re really still getting our heads around the event. You shred the star and then there’s this material that works 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. It’s an exciting place for scientists: right at the interface of the known and the unknown.
The the results have been reported at the 241st meeting of the American Astronomical Society in Seattle, Washington.
WATCH the NASA video…
FORWARD this Steller story to the Star-Gazers on social media…