In our Universe, collisions between black holes are not uncommon. But the one that astronomers have just observed is unlike any other. Because it takes place at the dawn of time. At a time when it is even hard to imagine that supermassive black holes could exist!
Our Universe is vast. However, cosmic objects occasionally collide. It is quite common, even for black holes. In the past decade, interferometers like Ligo and Virgo have detected around a hundred such collisions. Today, thanks to the data sent back by the James Webb Space Telescope, an international team of astronomers has been able to observe an ongoing collision between two supermassive black holes. This collision is somewhat special because it occurs when the Universe was no more than 740 million years old. Making it the farthest ever detected.
Black Holes of Tens of Millions Times the Mass of Our Sun
“We have found evidence of the presence of very dense gas with rapid movements near the black hole, as well as hot and highly ionized gas illuminated by the energetic radiation typically produced by black holes during their accretion episodes,” explains Hannah Übler, an astronomer at the University of Cambridge (UK), in a statement from the European Space Agency (ESA). “Thanks to the unprecedented sharpness of the images captured by the James Webb Space Telescope, we were able to spatially separate the two black holes.”
The system is known as ZS7. Its stellar mass is similar to that of our neighboring galaxy, the Large Magellanic Cloud.The Magellanic Cloud. Astronomers now tell us that it actually consists of two black holes with a mass probably around 50 million times that of the SunSun each.
Collisions of supermassive black holes and galaxy evolution
Researchers now know that such supermassive black holes are hidden in most massive galaxies in the local Universe, including our own Milky Way. They believe that these black holes have had a major impact on the evolution of these galaxies. However, they still do not fully understand how these objects became so massive, especially since finding such black holes already in place within the first billion years after the Big BangBig Bang indicates that their growth must have occurred very rapidly.
The results obtained here thanks to the James Webb Space Telescope confirm the role of massive black holes in galaxy evolution. They also suggest that the collision and mergermerger of black holes are an important pathway through which these massive objects can grow rapidly, even at the dawn of the Universe.
Gravitational waves after black hole merger
After the collision, once the two massive black holes have merged, they will generate gravitational wavesgravitational waves that could be detected by the next generation of interferometers like the Laser Interferometer Space Antenna (LisaLisa) mission. This mission has just been approved by ESA and will be the first space observatory dedicated to the study of gravitational waves. Given this recent discovery, researchers believe it could detect many more mergers of relatively light black holes than previously thought.
Meanwhile, astronomers will continue to use the James Webb Space Telescope to study in detail the relationship between supermassive black holes and their host galaxies during the first billion years of the Universe. They will systematically try to characterize black hole mergers to determine the speedspeed at which they occurred in the early cosmic epochs and evaluate their role in the early growth of black holes.