Nucleus, known as a center, may mean a lot of things. Reviewing your Biology, it is also known as the control center. Going to Chemistry, it is the center of an atom that has the protons and neutrons. Now, in Astronomy, you should know that the galaxy also has a nucleus. And it is called the galactic nucleus.

The galactic nucleus is the center of galaxies. It is normally small, luminous and contains interstellar materials and of course, stars. If a galaxy has an active galactic nucleus, it is called as an active galaxy. A galactic nucleus can be categorized as active if it emits greater radiation as other galactic nuclei cannot emit. Some galaxies have very active galactic nuclei that it can even have an enormous black hole.

Its luminosity emits electromagnetic radiation and helps scientists discover even distant space objects. There are even models of active galactic nucleus. These are accretion disk, which is formed by cold materials lying close to a central black hole, relativistic jets that are produced by accretion discs and radiantly inefficient active galactic nucleus that are produced by low strength radiation from huge black holes. The last one is least expected to have the characteristics of a standard active galactic nucleus with an accretion disc.