in the constellation Virgo
Roughly 1.5 billion times the mass of the Sun
Diameter roughly equal to the size of Neptune's orbit around the Sun, making it as big as our solar system.
M84 is a member of the Virgo Cluster, a grouping of hundreds of galaxies that travel through space as a unit, bound together by their mutual gravitational pull.
M84 has been classified as an elliptical galaxy, which means that it looks like a fuzzy egg or football, with little apparent structure. In recent years, however, some astronomers have suggested that it is a "lenticular" galaxy -- one that looks like a disk when seen from above, but a lens when seen from the side. In either case, M84 is larger and more massive than the Milky Way.
In 1997, observations with Hubble Space Telescope revealed that gas about 26 light-years from the center of M84 is orbiting at very high speeds. Only the gravitational pull of a supermassive black hole could account for this motion.
Early estimates said the central black hole in M84 must be at least 300 million times as massive as the Sun. With continued observations, however, astronomers have raised their estimates to about 1.5 billion times the mass of the Sun. That makes the black hole in M84 one of the largest and most massive yet discovered.
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This document was last modified: November 19, 2009.