Among the millions of galaxies that fill the vast universe, the vast majority are tranquil objects. And the others? A small part of the known galaxies is full of energy. What is its source? Probably supermassive black holes hiding in the nuclei of these active objects.
Artistic vision of jets from a supermassive black hole inside an active galaxy By ESA/Hubble, L. Cal莽ada (ESO) link [CC BY 4.0 license]
Most galaxies produce electromagnetic radiation of various types, such as visible light or infrared radiation. In most cases it has a stellar origin and is not something extraordinary. Active galaxies generate very strong radio and X-ray radiation. It is the result of processes taking place in the central areas of these objects. Nuclei of active galaxies are similar to quasars. Quasars are objects that produce huge amounts of energy. Some scientists believe that in the earlier stages of the development of the universe, active galaxies were quasars. Jets was observed in quasars and some active galaxies.
Inner structure of a galaxy with an active galactic nucleus By Rothwild link [CC BY-SA 3.0 license]
Jets are a stream of plasma particles that are ejected from the galactic nucleus in both directions. They carry huge amounts of energy and can reach many thousands of light years. The active galaxy M87 was examined and it was found that inside it there is a spinning disc, with the center of the diameter of our solar system. There are gigantic jets running out of it in both directions. The speed at which this disk spins is estimated to be over 500 km per second. Probably that the object in the center of the disk is a supermassive black hole with a mass of over 3 billion Suns! Most active galaxies are probably powered by central black holes.
