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 this famous cluster, it's challenging to spot with popular 7x50 or 10x50 binoculars. Larger models or small telescopes make this task easier but as with most galaxies, dark skies are essential. It's currently not certain what type of galaxy M84 is; it could be a type S0 lenticular galaxy seen face-on or an elliptical galaxy of type E1.

Charles Messier discovered M84 on March 18, 1781 during one of his regular nightly patrols. He also discovered and catalogued another eight objects on the same day, including M86 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 to the east.

The Virgo cluster galaxies are best seen during the months of March, April and May.

M84 Galaxy (credit:- Gary Bower, Richard Green (NOAO), STIS Instrument Definition Team and NASA/ESA)

Finder Chart for M84 (credit:- freestarcharts)

Finder Chart for M84 - pdf format (credit:- freestarcharts)

Both M84 and M86 are visible together in the same low-power field of view. Refractors of the order of 80mm (3.1-inch) aperture, reveal them as small faint oval shapes of light with brighter centers. The other halos suffer from low surface brightness and therefore are better seen with larger scopes. Through 200mm (8-inch) reflectors, it's possible to 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 giant elliptical galaxy, M87.

Recent radio and Hubble Space Telescope observations have revealed two jets of matter shooting out from the centre of M84. This galaxy contains few young stars, suggesting star formation is occurring at a slow rate. In total, M84 contains about 400 billion stars. To date, three supernovae have been observed (SN 1957B, SN 1980I and SN 1991bg). They all peaked between magnitudes +13 and +14.

M84 Data Table

Messier84
NGC4373
Object TypeLenticular galaxy (or Elliptical galaxy)
ClassificationS0 (or E1)
ConstellationVirgo
Distance (light-years)60 Million
Apparent Mag.+9.4
RA (J2000)12h 25m 05s
DEC (J2000)+12d 53m 13s
Apparent Size (arc mins)6.5 x 5.6
Radius (light-years)55,000
Number of Stars400 Billion
Notable FeatureCould be either a lenticular galaxy seen face-on or an elliptical galaxy

Sky Highlights - September 2017

Opposition
Neptune reaches opposition on September 5th

The Planets
This Month's Guide

Algol Minima
Algol eclipse dates and times for September

Northern Hemisphere
Evening
West:- Jupiter (mag. -1.7)
Southwest:- Saturn (mag. +0.5)
East:- Neptune (mag. +7.8)
Midnight
South:- Neptune
East:- Uranus (mag. +5.7)
Morning
West:- Neptune
South:- Uranus
East:- Venus (mag. -3.9), Mars (mag. +1.8) (from second week), Mercury (mag. +0.5 to -1.3) (from second week)

Southern Hemisphere
Evening
West:- Jupiter
Northwest:- Saturn
East:- Neptune
Midnight
West:- Saturn
North:- Neptune
Northeast:- Uranus
Morning
West:- Neptune
Northwest:- Uranus
Northeast:- Venus
East:- Mars (end of month)

Deep Sky

Small telescopes:-
Messier 13 - M13 - Great Hercules Globular Cluster
Messier 92 - M92 - Globular Cluster
Messier 11 - M11 - The Wild Duck Cluster (Open Cluster)
Messier 7 - M7 - The Ptolemy Cluster (Open Cluster)
Messier 6 - M6 - The Butterfly Cluster (Open Cluster)
Messier 4 - M4 - Globular Cluster
Messier 8 - M8 - Lagoon Nebula (Emission Nebula)
Messier 16 - M16 - Eagle Nebula (Emission Nebula with Open Cluster)
Messier 20 - M20 - Trifid Nebula (Emission and Reflection Nebula)

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