M90 is a spiral galaxy located in Virgo. It's a member of the Virgo Cluster and one of the largest and brightest spirals in the group. With an apparent magnitude of +9.6, it's visible through small scopes as a reasonably bright oval shaped patch of light. M90 appears bright in medium size telescopes but to spot the spiral structure requires a larger amateur scope.
The galaxy was one of eight galaxies, all Virgo members, discovered by Charles Messier on March 18, 1781. It's located about 60 Million light-years distant and is intrinsically large with an actual diameter of 165,000 light-years, more than the Andromeda Galaxy (M31). It's estimated to contain a trillion stars.
M90 is positioned close to the centre of the Virgo cluster and right at the Virgo-Coma Berenices constellation boundary. The centre of the cluster is located roughly halfway along a line connecting stars, Denebola (β Leo - mag. +2.1) and Vindemiatrix (ε Vir - mag. +2.8). In the same area of sky are M84, M86 and M87 with M90 positioned 1.5 degrees northeast of M87. The small elliptical galaxy M89 is 0.75 degrees southwest of M90 with M91 about a degree to the north-northwest of M90. Tenth magnitude spiral galaxy M88 is located 1.5 degrees northwest of M90.
The Virgo galaxies are best seen during the months of March, April and May.
M90 can be spotted with 7x50 or 10x50 binoculars but requires dark skies and excellent seeing conditions. It's easier to see with small scopes; an 80mm (3.1-inch) instrument reveals a reasonably bright oval shaped smudge of light but nothing much else. When viewed through a 200mm (8-inch) scope, M90 has a bright core surrounded by a streak of nebulosity that fades outwards from the centre. On dark nights, larger amateur scopes hint at more detail including the spiral arms. In total, M90 spans 9.5 x 4.4 arc minutes of apparent sky.
The galaxy is one of a few that appear blueshifted. This results from its large velocity within the Virgo Cluster, which means that it's currently moving towards us. Only one Messier galaxy is approaching us faster, M86. This is in contrast to most other galaxies which are redshifted and therefore receding from us.
M90 Data Table
|Object Type||Spiral galaxy|
|RA (J2000)||12h 36m 50s|
|DEC (J2000)||13d 09m 45s|
|Apparent Size (arc mins)||9.5 x 4.4|
|Number of Stars||1 Trillion|
|Notable Feature||Very large spiral galaxy belonging to the Virgo Cluster of galaxies|