One of the greatest mysteries of the cosmos concerns supermassive black holes, extreme objects that become huge thanks to the fact that they “devour” everything around them, from the stars to the planets. According to what astronomers have observed, however, these black holes have existed since the universe was very young.
So how did black holes get so big? A new study could be a step towards solving the puzzle. The researchers, led by Violette Impellizzeri of the National Radio Astronomy Observatory (NRAO), observed the supermassive black hole within the galaxy NGC 1068, also known as Messier 77, a spiral galaxy distant from us about 47 million light-years. At the center of this class, in fact, there is a so-called “active galactic nucleus,” essentially a supermassive black hole that continually swallows matter and which boasts all-around a growth disc composed of the same material that swallows matter.
Previous research had already shown that this black hole is not limited to swallowing the material but also emits strong gusts of gas at a speed of up to 300 miles per second. Using the target of the ALMA telescope in Chile, the researchers carefully observed the gas around the black hole and identified two counter-rotating gas discs. One, the inner one, is 2-4 light-years and rotates in the same direction as the rotation of the galaxy. The other one, the outer one, is up to 22 light-years and rotates in the opposite direction.
It was something unexpected for the astronomers themselves as the gas and materials that are attracted to the black hole or that otherwise revolve around it in the accretion disk usually turn in only one direction. When they do not turn this way and there is a “counter-rotating” element it means that the same counter-rotation is caused by the interaction with another galaxy but it does not seem to be the case with NGC 1068, where the phenomenon develops on a very large scale smaller, a few tens of light-years.
According to the astronomers, therefore, this counter-rotating gas may have been caused by gas clouds or a small galaxy that passed close and was captured by the disk. In any case the external disk will begin to touch the internal one, which could happen already in a few hundred thousand years. This will provoke a violent confrontation, considering that they rotate in different directions, and a collapse of both disks, an event that turns out to be very bright but that will only be able to observe our distant ancestors.
This study may perhaps prove to be very useful for understanding the evolution of gas flows around supermassive black holes and perhaps even explaining the formation of older ones.