M77 - CETUS A

Messier 77 (NGC 1068), also known as Cetus A, is a barred spiral galaxy located approximately 47 million light-years from Earth in the constellation Cetus. It was discovered by Pierre Mechain in 1780 and is one of the largest and most luminous galaxies in the Messier catalog, spanning approximately 170,000 light-years in diameter including its faint outer extensions. M77 is the closest and brightest example of a Seyfert galaxy, a type of active galaxy with an extremely luminous nucleus powered by a supermassive black hole actively accreting matter. The central black hole of M77 has an estimated mass of about 15 million solar masses, and the accretion disk surrounding it produces intense radiation across the electromagnetic spectrum, from radio waves to X-rays. The galaxy played a pivotal role in the development of the unified model of active galactic nuclei, which proposes that different types of active galaxies (Seyfert 1, Seyfert 2, quasars) are actually the same phenomenon viewed from different angles relative to a dusty torus surrounding the central engine. M77 is classified as a Seyfert 2, meaning our line of sight passes through this obscuring torus, hiding the broad emission lines from the inner accretion disk. The VLTI interferometer has directly imaged the dusty torus around M77's nucleus, providing key evidence for the unified model. In amateur telescopes, M77 appears as a bright, round galaxy with a conspicuously luminous, star-like nucleus. A 4-inch telescope shows the bright core and diffuse halo, while larger instruments can reveal hints of the spiral structure surrounding the active nucleus.

M77 spans approximately 170,000 light-years in diameter and lies about 47 million light-years from Earth, hosting a 15 million solar mass central black hole.