|Designation|| Messier 84|
|Right ascension||12h 25m 03.7s|
|Declination||+12° 53′ 13″|
|Type of object||Lenticular galaxy|
|Magnitude|| Apparent Mag: +10.1|
Absolute Mag: -20.5
|Distance from Earth||57.8 million light-years|
|Radial velocity||979±30 km/s|
Messier 84 (M84, NGC 4374) is a lenticular galaxy in the constellation of Virgo. One of the more luminous members of the Virgo galaxy cluster, it was first observed by Charles Messier in 1781. Astrophotography by the Hubble Space Telescope in the visual and studies into the radio emissions of M84 suggest there may be a supermassive black hole at the centre of the galaxy. The galaxy is classified as type S0.
Messier 84 was discovered by Charles Messier on March 18, 1781 along with 7 other members of the Virgo cluster. He described it as a, "nebula without star, in Virgo; centre is a bit brilliant, surrounded with a slight nebulosity." He further remarked of the similarities to Messier 59 and Messier 60. Later John Herschel catalogued the galaxy as h 1237 and as GC 2930 in his General Catalogue, a predecessor to the New General Catalogue.
Environment and Structure
Messier 84 has an angular size of around 6.5x5.6 arc minutes, corresponding to a physical radius of 55,000 light-years. While most sources state it is a lenticular galaxy of type S0, some suggest it may in fact be an elliptical galaxy with a very low eccentricity, perhaps of type E1. The reason for this confusion is the orientation of the galaxy, whether it is observed face on or not. The galaxy, estimated to contain around 400 billion stars, is located in the inner regions of the Virgo cluster. The galaxy also possesses large dust lanes.
Photography performed by the Hubble Space Telescope in 1997 and radio studies of the galaxies have unveiled two jets of matter being ejected from the galaxy's core. While not unique, this is uncommon. In addition to this, spectroscopic analysis of the radio emissions imply there is a disk of stars and gas rotating rapidly about the centre of M84. Some present this as evidence for a supermassive black hole, with estimates of such an objects mass ranging from 300 million solar masses to 1.5 billion solar masses.
At least two supernovae have been detected in M84. The first, with and apparent magnitude of +13, was SN 1957B which occurred on May 18, 1957. The second was SN 1991bg, slightly fainter at an apparent magnitude of +14 in December 1991. The third was SN 1980I, discovered on June 13, 1980. The last one is contested as to whether it actually occurred in the M84 galaxy, it may have occurred in Messier 86 or NGC 4387, neighbouring galaxies of Messier 84. All three supernovae are thought to be Type 1a supernovae, caused by the accretion of matter onto a white dwarf.
- Messier 84 from messier-objects.com
- Messier 84 from simbad.u-strasbg.fr
- Entry on Messier 84 from Messier's Nebulae and Star Clusters, Kenneth Glyn jones, from books.google.co.uk
- M84 from astropixels.com
- Messier 84 from freestarcharts.com
- messier 84 from messier.seds.org
- Hubble Space Telescope images of M84 from messier.seds.org