Sophia Dagnello, NRAO/AUI/NSF
In October 2018, a black hole in a galaxy 665 million light-years from Earth devoured a star that had fallen into its gravitational grasp. An object with a mass of 1/10 the mass of the Sun ruptured in front of scientists who watched the entire phenomenon. The thing is that almost 3 years after the event, astronomers discovered something that had not yet been seen: the same black hole – not devouring other stars in the meantime – released a huge stream of matter, moving at almost half the speed of light. . While we are already used to similar events, it is not too late yet.
Violent encounters between black holes and stars are known as tidal disturbance events (TDEs); During it, the interaction of intense tidal forces leads to the start of the “spaghetti” process, in which the star torn apart by the black hole is gradually stretched, compressed horizontally, eventually taking the shape resembling a spaghetti noodle. In 1 in 5 TDEs, stellar material falling onto the black hole’s accretion disk is heated to the point where it is ejected into space at tremendous speed – such phenomena occur during the first weeks or months of devouring a star. However, it was never observed years after the event, not to mention the fact that as a result of the above-described confluence between the black hole and the star, ejected matter moves about 5 times faster than in the case of other TDEs.
Yvette Sindis of the Harvard and Smithsonian Center for Astrophysics comments on the situation:
This totally surprised us – no one had ever seen anything like this.
The issue was also taken up by Harvard University astronomy professor Edo Berger, co-author of the new study:
We have used radio telescopes to study the phenomenon of TDE for more than a decade. Sometimes we find that they glow in the radio wave band when material is ejected during the first consumption of a star by a black hole. But in the case of this event, there was radio silence for the first three years – now there was a violent thunderbolt. This is one of the most incandescent radio TDEs we’ve ever seen.
Both worlds offer several explanations for the trajectory of the phenomenon:
- The flow of matter formed after falling on the accretion disk of a black hole may be very weak in the first period after the destruction of the star and its activity “started” with changes in the disk itself;
- The magnetic field of a predatory star may be too weak to begin the process of formation of a plasma flow (jet) – its composition was determined by the influence of the magnetic field of the accretion disk;
- This kind of material ejection may be—years after the star’s absorption—more frequent than previously thought; So far, astronomers stop observing TDE a few months after the event, and rarely look at the phenomenon’s long-term consequences.
“Infuriatingly humble musicaholic. Problem solver. Reader. Hardcore writer. Alcohol evangelist.”