M84 is a magnitude +9.4 lenticular or elliptical galaxy that belongs to the Virgo cluster of galaxies. Although one of the brighter members of the famous cluster, it's challenging to spot with popular 7x50 or 10x50 binoculars. Larger binoculars such as 20x80s or small telescopes make the task easier but as with most galaxies, dark skies are important. It's currently not clear what type of galaxy M84 is, it could either be a lenticular galaxy of type S0 seen face-on or an elliptical galaxy of type E1.
Charles Messier discovered M84 during one of his regular night sky patrols on March 18, 1781. He also discovered and catalogued another eight objects on the same day including M86, another giant lenticular or elliptical galaxy that's positioned just east of M84. The apparent size of M84 is 6.5 x 5.6 arc minutes and it's about 60 Million light years distant. This corresponds to a spatial diameter of 110,000 light-years.
M84 lies at the heart of the Virgo Cluster, close to the Virgo-Coma Berenices constellation border. It can be found by imagining a line connecting Denebola (β Leo - mag. +2.1) to Vindemiatrix (ε Vir - mag. +2.8). At the centre point of this line is M84 with M86 positioned 17 arc minutes east of M84.
The Virgo cluster galaxies are best seen during the months of March, April and May.
Both M84 and M86 are visible together in the same low-power field of view. Small telescopes of the order of 80mm (3.1-inch) reveal both galaxies as small faint oval shapes of light with brighter centers. The other halos have low surface brightness, hence are better seen with medium or large sized scopes. Through a 200mm (8-inch) telescope under dark sky conditions, it's possible to also spot several more galaxies in the same field of view, including NGC 4435, NGC 4388, NGC 4402 and NGC 4438. Located about 1.5 degrees southeast of the M84/M86 pair is the giant elliptical galaxy M87.
Recent radio and Hubble Space Telescope observations have revealed two jets of matter shooting out from the centre of M84. The galaxy also has few young stars, indicating star formation is taking place at a slow rate. To date, three supernovae have been observed in M84 (SN 1957B, SN 1980I and SN 1991bg). The first one reached magnitude +13, the others magnitude +14. In total M84 contains about 400 billion stars.
M84 Data Table
|Object Type||Lenticular galaxy (or Elliptical galaxy)|
|Classification||S0 (or E1)|
|RA (J2000)||12h 25m 05s|
|DEC (J2000)||12d 53m 13s|
|Apparent Size (arc mins)||6.5 x 5.6|
|Number of Stars||400 Billion|
|Notable Feature||Could be either a lenticular galaxy seen face-on or an elliptical galaxy|