An international team of astronomers has detected a rare burst of light coming from a star torn apart by a supermassive black hole, a phenomenon known as “tidal disruption” and which is the closest observed so far. The observation was made possible with the telescopes of the European Southern Observatory (ESO) and other organizations around the world and the event happened just over 215 million light years from Earth.

Roger Penrose, Reinhard Genzel and Andrea Ghez win the Nobel Prize in Physics for their discoveries about black holes

“The idea of ​​a black hole sucking to a nearby star sounds like science fiction. But that’s exactly what happens in a tidal disruption event, “said Matt Nicholl, professor and researcher at the Royal Astronomical Society at the University of Birmingham, UK, and lead author of the new study. ESO said in a statement that these tidal disruption events, where a star experiences what is known as spaghetti when being sucked into a black hole, “are rare and not always easy to study.”

In order to investigate in detail what happens when a star is eaten by such a monster, the research team pointed ESO’s VLT (Very Large Telescope) and NTT (New Technology Telescope) at a new flash of light that took place last year near a supermassive black hole.

In theory astronomers know what should happen in such a situation. According to Thomas Wevers, another of the researchers who participated in the observation, “when an unfortunate star wanders too close to a supermassive black hole in the center of a galaxy, the extreme gravitational pull of the black hole rips the star apart, ripping out fine streams of material. “. As some of those fine strands of stellar matter fall into the black hole during this process a bright blaze of energy is released that astronomers can detect.

Although powerful and bright, experts have so far had trouble investigating these bursts of light that often are obscured by a curtain of dust and debris. Now however they have been able to advance the knowledge about the origin of this curtain.

The idea of ​​a black hole sucking in a nearby star sounds like science fiction

“We discovered that when a black hole devours a star, it can launch a powerful blast of matter outward that obstructs our view,” explains Samantha Oates of the University of Birmingham. He adds that this happens because the energy released when the black hole feeds on stellar material pushes the debris from the star outward. The discovery was made possible because the tidal disruption event the team studied, AT2019qiz, was detected shortly after the star was shattered.

“Actually, thanks to our early detection, we could see the curtain of dust and debris forming as the black hole launched a powerful jet of material with speeds of up to 10,000 kilometers per second“, explains Kate Alexander, postdoctoral researcher (NASA Einstein Fellow) at Northwestern University (United States).” This look behind the curtain it was our first opportunity to identify the origin of the obscuring material and to follow in real time how it envelops the black hole, “he adds.

Six months

Over a period of six months, during which the flare grew in luminosity and then faded, the team conducted observations of AT2019qiz, located in a spiral galaxy, in the constellation Eridanus. “Several soundings detected the emission of the new tidal disruption event very shortly after the star was shattered,” says Wevers, indicating that they immediately pointed to the array of ground and space telescopes in that direction to see how the star was produced. light.

Artist's rendering of the merger of two black holes like the ones that gave rise to GW190521.
They discover the “chirps” that black holes emit when they collide

In the following months, multiple observations of the event were carried out with other facilities. Celerity and extensive observations in ultraviolet light, optical range, X-rays and radio waves revealed, for the first time, a direct connection between the material flowing from the star and the bright flash emitted as it is devoured by the black hole. .

“Observations showed that the star was approximately the same mass as our own Sun and that the monstrous black hole, which is more than a million times more massive, had caused it to lose about half that mass, “according to Nicholl. The team of astronomers believe AT2019qiz could even act as a” Rosetta stone “to interpret future observations of tidal disruption events.

On the other hand, ESO’s ELT (Extremely Large Telescope), which is expected to start operations this decade, will allow researchers to detect increasingly weak and rapidly evolving tidal disruption events in order to solve more mysteries of the physics of black holes.