Astronomers find star recently ripped apart by black hole

An illustration shows the the tidal disruption of an unlucky star when it meets a supermassive black hole. Photo by Robin Dienel/Carnegie Institution for Science
An illustration shows the the tidal disruption of an unlucky star when it meets a supermassive black hole. Photo by Robin Dienel/Carnegie Institution for Science

Sept. 26 (UPI) -- NASA's Transiting Exoplanet Survey Satellite has spotted the remnants of a star that was recently shredded by a supermassive black hole -- a first.

Astrophysicists and cosmologists estimate supermassive black holes are located at the center of most galaxies. When stars wander too close, a black hole's tremendous gravitational pull can rip it apart. The violent interaction is known as a tidal disruption event, or TDE.


Scientists can come to better understand the dynamics of black holes by studying the spectral signatures of TDEs.

The tidal disruption event ASASSN-19bt was first spotted by an international network of telescopes called the All-Sky Automated Survey for Supernovae. TESS was able to observe the TDE, as well, providing complementary images of the event.

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When a star is ripped apart by a supermassive black hole, it peaks in brightness before tapering off. The NASA space telescope utilizes a wide field-of-view and continuous viewing, allowing it to capture the sudden spike in brightness in fine detail.

The newest images of ASASSN-19bt revealed the evolution of the shredded star in unprecedented detail.

"Only a handful of TDEs have been discovered before they reached peak brightness and this one was found just a few days after it started to brighten; plus, thanks to it being in what's called TESS' 'Continuous Viewing Zone,' we have observations of it every 30 minutes going back months -- more than ever before possible for one of these events," Thomas Holoien, astronomer at the Carnegie Institution for Science, said in a news release. "This makes ASASSN-19bt the new poster child for TDE research."

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Scientists were able to get a comprehensive picture of the tidal disruption event by coupling ground-based and space-based observations.

"I was actually observing at Carnegie's Las Campanas Observatory on the night of the discovery," Holoien added. "So, I was able to take spectra with our du Pont and Magellan telescopes less than a day after the event was first seen in South Africa by part of ASAS-SN's network."

By analyzing the spectral patterns -- the changes in different frequencies of light produced by the event -- scientists can identify the chemical composition and speed of materials being shredded by the black hole.

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The latest findings, published this week in the Astrophysical Journal, suggest TDEs are more variable than astronomers previously thought.

Scientists found ASASSN-19bt in a galaxy that is younger and more dust-filled than the types of galaxies that typically host TDEs. The spectral patterns also revealed a brief period of cooling and fading prior to the buildup to the shredded star's peak brightness. Despite the blip, the data showed ASASSN-19bt approached peak brightness surprisingly smoothly.

"Having so much data about ASASSN-19bt will allow us to improve our understanding of the physics at work when a star is unlucky enough to meet a black hole," said Carnegie's Decker French.

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