Saturday, Jun 22, 2024

Messier 100 (M100), also known as NGC 4321, is a spiral galaxy located in the direction of the constellation Coma Berenice, at a distance of 55 million light-years from us. M100 was discovered by Pierre Méchain in 1781 and included by his friend Charles Messier in his catalog a few weeks later; the latter determined its coordinates and also provided a brief description. William Herschel studied this galaxy very carefully, precisely because of the presence of some chiaroscuro on the surface of the halo; he even believed he had identified a small cluster of stars inside it, while his son John was unable to find it. Lord Rosse compared its central part to a planetary nebula, while he was able to clearly distinguish the spiral structure of the halo. The exact distance of the galaxy was estimated in 1993 when the Hubble Space Telescope managed to observe 20 Cepheids inside it and estimate their period.