M90 is a spiral galaxy located in Virgo that's a member of the Virgo Cluster and one of the group's largest and brightest spirals. With an apparent magnitude of +9.6, it's visible with small scopes, appearing as an oval shaped patch of light. M90 shines relatively bright in medium size reflectors, but spotting the spiral structure is difficult and larger scopes are recommended.
This 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 away and is intrinsically large, with an actual diameter of 165,000 light-years. This equates to about 20% more than the diameter of the Andromeda Galaxy (M31). M90 is estimated to contain a trillion stars.
The galaxy is positioned close to the centre of the Virgo cluster and right at the Virgo-Coma Berenices constellation border. The centre of the Virgo 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. M90 is positioned 1.5 degrees northeast of M87. The small elliptical galaxy, M89, is 0.75 degrees southwest of M90 with M91 about a degree 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 dark skies and excellent seeing conditions are required. It's easier to glimpse with small scopes, such as 80mm (3.1-inch) refractors. With such instruments a reasonably bright oval smudge can be made out but not much else. When viewed through 200mm (8-inch) reflectors, M90 has a bright core surrounded by a streak of nebulosity that fades outwards from the centre. On dark nights, large amateur scopes hint at more detail including the spiral arms. In total, it spans 9.5 x 4.4 arc minutes of apparent sky.
This galaxy is one of a few that appears blueshifted from our perspective, which means it's currently moving towards us. Only one other Messier galaxy is approaching us faster and that's M86. Due to the expansion of the Universe, the vast majority of galaxies are receding and therefore appear redshifted.
M90 Data Table
|Object Type||Spiral galaxy|
|Distance (light-years)||60 Million|
|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|