M84
Messier 84 or M84, also known as NGC 4374, is an elliptical or lenticular galaxy in the constellation Virgo. Charles Messier discovered Messier 84 on 18 March 1781 in a systematic search for "nebulous objects" in the night sky. The object is the 84th in the Messier Catalogue. M84 is situated in the heavily populated inner core of the Virgo Cluster of galaxies.
This is a giant elliptical galaxy with a morphological classification of E1, indicating a flattening of 10%. The half-light radius is 72.5″ and the extinction-corrected total luminosity in the visual band is 7.64×1010 L☉. The central mass-to-light ratio is 6.5, which steadily increases away from the core. The visible galaxy is surrounded by a massive dark matter halo.
Radio observations and Hubble Space Telescope images of M84 have revealed two jets of matter shooting out from the galaxy's center as well as a disk of rapidly rotating gas and stars indicating the presence of a 1.5 ×109 M☉ supermassive black hole. It also has a few young stars and star clusters, indicating star formation at a very low rate. The number of globular clusters is 1,775±150, which is much lower than expected for an elliptical galaxy.
Two supernovae have been observed in M84: SN 1957 and SN 1991bg. Possibly, a third, SN 1980I is part of M84 or, alternatively, one of its neighbouring galaxies, NGC 4387 and M86. This high rate of supernova events is rare for elliptical galaxies, which may indicate there is a population of stars of intermediate age in M84.
