Radio observations and Hubble Space Telescope images of M84 have revealed two jets of matter shooting out from its center as well as a disk of rapidly rotating gas and stars indicating the presence of a 1.5 ×109M☉[9] supermassive black hole. It also has a few young stars and star clusters, indicating star formation at a very low rate.[10] The number of globular clusters is 1,775±150, which is much lower than expected for an elliptical galaxy.[11]
Viewed from Earth its half-light radius, relative angular size of its 50% peak of lit zone of the sky, is 72.5″, thus just over an arcminute.
Two supernovae have been observed in M84: SN 1957B[12]
and SN 1991bg.[13] Seen between these dates, it may have bore a third, SN 1980I – which may have been in either neighboring galaxy NGC 4387 or M86.[14] This high rate of supernovae is rare for elliptical galaxies, which may indicate there is a population of stars of intermediate age in M84.[11]
^Ford, Alyson; Bregman, J. N. (2012). "Detection of Ongoing, Low-Level Star Formation in Nearby Ellipticals". American Astronomical Society. 219: 102.03. Bibcode:2012AAS...21910203F.