M100 is located in the constellation Coma Berenices but is actually a member of the Virgo cluster of galaxies. It is one of the brightest members of the Virgo Cluster and can be viewed in moderate amateur telescopes. Two "dwarf" galaxies are prominant in this image and are also members of the Virgo Cluster. Gravitational interaction with these, and other galaxies of the Virgo Cluster, is probably the cause of the slightly asymmetric shape of its spiral structure. The Hubble Space Telescope was used to observe M100 and 20 Cepheid Variable stars were identified. Using these stars as a distance measuring "guide post" the distance to the galaxy has been determined to be 56 million light years. (+/- 6 ly)

¹http://www.seds.org/messier/m/m100.html