Black holes send out massive lightning strikes

In the life cycles of all supermassive black holes in the centers of galaxies there are likely periods when these black holes absorb matter from their immediate surroundings. But that's where the similarities end. This is the conclusion reached by British and Dutch astronomers who observe a well-studied area of ​​the sky with an oversensitive radio telescope.

Astronomers have been studying active galaxies since the 1950s. In the centers of active galaxies there are supermassive black holes that consume matter. During these active phases, these objects often emit extremely strong radio, infrared (IR), ultraviolet (UV) and X-rays.

In the new study, astronomers turned their attention to all active galaxies in the well-studied sky region GOODS-North, which lies in the direction of the constellation Ursa Major. So far, this region of space has mainly been studied with space telescopes that work with optical, IR and UV light. To these data in the new work, the researchers added data from observations made with a network of sensitive radio telescopes, including the UK observatory's national facility e-MERLIN and the European VLBI network (EVN).

Through systematic research, astronomers have identified three main points. First, it turned out that the cores of galaxies of different types have different activities. Some black holes are extremely insatiable and use up as much material as possible. other supermassive black holes "chew" their food more slowly, while some black holes "starve".

Second, sometimes the accretion phase coincides with the formation of new stars, sometimes it doesn't. As star formation continues in the galaxy, activity in the core becomes more difficult to see.

Thirdly, due to the accretion processes occurring in the nucleus, radio waves may or may not be emitted - regardless of the speed at which the black hole takes in its "food".

According to lead author Jack Radcliffe of the University of Pretoria, South Africa, the observations also show that radio telescopes are optimal for studying the "eating habits" of black holes in the distant universe. "This is good news because the completion of the SKA radio telescopes is just around the corner and will allow us to look deeper into the universe and learn new information about its functions."

Two papers on the results of this study were published in the journal Astronomy & Astrophysics.