Messier 84 (also known as NGC 4374) is a lenticular or elliptical galaxy, situated in the heavily populated inner core of the Virgo Cluster of galaxies.
Messier 84 and 86 were both discovered on March 18, 1781 by Charles Messier, along with five more nebulous objects in the same celestial region. All are member galaxies of the Virgo Cluster.
Amateur Observation
At magnitude 9.1, M 84 is one of the brighter members of the Virgo Cluster; it appears 5' across in size. Messier 84 marks the beginning of Markarian's Chain of galaxies that runs northeast from M 84 to Messier 88 in Coma Berenices. The giant ellipticals and spirals in this area, along the Virgo-Coma Berenices border, form the core of the Virgo Supercluster.
From its appearance, M 84 is either an elliptical galaxy of type E1, or a lenticular galaxy of type S0 seen face-on. It is populated by old, yellowish stars, and surrounded by a nice system of globular clusters.
Physical Properties
The best distance estimate of the center of the Coma-Virgo Group is 65 million light years. If M 84 is this far away, then its absolute magnitude is -22.4, giving it a very impressive luminosity of 76 billion suns, and its true diameter is over 100,000 light years. Its mass has been calculated to be about 500 billion suns.
Radio observations and Hubble Space Telescope images M 84 have revealed two jets of matter ejected from the galaxy's center, as well as a rapidly rotating disk of stars and gas close to the nucleus. These indicate the presence of a supermassive black hole, of 18 million solar masses, in the galaxy's nucleus.
Three supernovae have been observed in M84: SN 1957B, SN 1980I, and SN 1991bg. Supernovae are rare events for elliptical galaxies, and it is unusual for M 84 to have produced so many.