Supermassive black hole ‘spaghettifies’ doomed star in tidal disruption event

An artist’s impression of a star in the process of being sucked in toward a supermassive black hole, undergoing “spaghettification” as its atmosphere is pulled away in thin streams of material. Image: ESO/M. Kornmesser

Astronomers have managed to study in detail a rare blast of light from a star being devoured as it was sucked in toward a supermassive black hole. Undergoing a process known as “spaghettification,” the doomed star’s atmosphere was pulled away, stretched and compressed into thin streams by the black hole’s titanic gravity.

Astronomers at the European Southern Observatory and other institutions carried out a detailed set of observations focused on AT2019qiz, a tidal disruption event that was discovered in a spiral galaxy in the constellation Eridanus shortly after the shredding began. At 215 million light years away, it is the nearest such flare detected to date.

“The idea of a black hole ‘sucking in’ a nearby star sounds like science fiction,” said Matt Nicholl, a Royal Astronomical Society research fellow at the University of Birmingham and lead author of a study in Monthly Notices of the Royal Astronomical Society. “But this is exactly what happens in a tidal disruption event.”

Material from a shredded star is heated to enormous temperatures as it is pulled into the black hole, generating detectable flares. But up to now, astronomers have had trouble studying such events in detail because they are obscured by intervening clouds of gas and dust.

The observations of AT2019qiz show the flare-shrouding material in this case was a result of the tidal disruption event itself.

“We found that, when a black hole devours a star, it can launch a powerful blast of material outwards that obstructs our view,” said Samantha Oates, a researcher at the University of Birmingham.

Because astronomers were able to catch AT2019qiz early in the process, “we could actually see the curtain of dust and debris being drawn up as the black hole launched a powerful outflow of material with velocities up to 10,000 (kilometres per second),” said Kate Alexander, a NASA Einstein Fellow at Northwestern University in the United States.

“This unique peek behind the curtain provided the first opportunity to pinpoint the origin of the obscuring material and follow in real time how it engulfs the black hole.”

The team studied AT2019qiz over a six-month period as the flare brightened and then faded away, making observations across the electromagnetic spectrum, from ultraviolet, X-ray and optical emissions to radio waves, finding a direct connection between the material flowing outward from the star and the flare generated as the black hole feasted on the star’s debris.

“The observations showed that the star had roughly the same mass as our own Sun, and that it lost about half of that to the monster black hole, which is over a million times more massive,” said Nicholl.

The research promises to shed more light on how matter behaves in the extreme-gravity environment of a supermassive black hole and may help astronomers interpret future observations of tidal disruption events.