Messier 91 or M91 (also designated NGC 4548) is a barred spiral galaxy in the constellation Coma Berenices. It has an apparent visual magnitude of 10.2 and its angular diameter is 5.4x4.4 arc-minutes. M91 lies at an estimated distance of 60 million light years. The Equinox 2000 coordinates are RA= 12h 35.5m, Dec= +14° 30´ which makes M91 best seen during the spring. The Messier Spring Star Chart shows the position of all Messier objects visible during that season.

The image above shows the uncropped view of M91 (left) and M88 (right) through the Takahashi E-180 Astrograph (North is up). A 3x enlargement of this image centered on M91 appears to the right.

This galaxy was discovered by Messier in 1781 and is a member of the Virgo Cluster of galaxies. It is one of four barred spiral galaxies included in the Messier Catalog (M58, M91, M95, and M109).

According to Stoyan et al. (2010), the distance of M91 is 52.9 million light years and its diameter is 83,000 light years.

For more information, see the Messier Catalog as well as specific entries for M91 in Wikipedia and SEDS.

Messier's Description of M91

March 18, 1781
`Nebula without star, in Virgo, above the preceding No. 90: its light is still fainter than that of the above.'

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