Active galactic nuclei are galaxies that release massive amounts of energy and are extremely luminous, emitting radio waves and visible light. They typically have a supermassive black hole at the center, surrounded by an accretion disk and torus. Some have two relativistic jets. AGN include quasars, blazars, radio galaxies, and Seyfert galaxies. Astronomers study AGN to understand galactic evolution and evolution of the universe, as they are extremely luminous and can provide insights into early universe.
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