In early 2022, the Zwicky Transient Facility (ZTF) observatory detected an extraordinary flash from the Mount Palomar in California. The scientists who studied the flash determined that it was a jet produced by a black hole devouring a star. Most galaxies contain supermassive black holes in their central regions, which contain up to billions of times the mass of the Sun. Despite their intense gravitational field, these black holes show a structure formed by a gas and dust disk, which absorbs material from their surrounding. However, for much of the time, these supermassive black holes do not devour anything, making an event like this an opportunity to study the neighborhood of the gravitationally most powerful objects in the universe.
Usually, when a star gets too close to a black hole, it is violently torn apart by the tidal forces of the black hole. The black hole then captures pieces of the star in a disk that revolves rapidly around it before finally consuming it. This is what astronomers call a tidal disruption event (TDE). However, in extremely rare cases, the black hole ejects relativistic jets of matter that travel at nearly the speed of light. The scientists who studied the flash from the ZTF observe that such jets are produced only 1% of the time.
The TDE that occurred from the black hole that produced the flash observed by the ZTF, known as AT2022cmc is among the most luminous ever observed and the most distant TDE ever detected. It seems to be at the center of a galaxy that is not (yet) visible because its light was eclipsed by AT2022cmc. However, when this episode is over, the galaxy could be photographed by the Hubble or James Webb space telescopes.
Astronomers suggest that the black hole’s rotation velocity is associated with the production of jets. The continuous monitoring of the skies is essential to discovering these types of extreme events like TDEs. In the coming years, the appearance of more powerful telescopes, like the LSST, could lead to the detection of more TDEs that could help clarify how supermassive black holes grow and shape the galaxies around them.
The scientists involved in the study suggest that AT2022cmc aimed almost directly at Earth, which made it appear brighter than if it had been pointing in any other direction. This phenomenon is referred to as relativistic Doppler boosting. The scientists conclude that the relativistic jet in the AT2022cmc event was moving at a speed of 99.9% the speed of light.
The community of astronomers is constantly searching for such extreme events to understand how plasma jets and radiation are created and why a small fraction of the TDEs produce them. While the rarity of these events makes them difficult to observe, they offer a unique opportunity to study the universe’s most powerful objects.