GALAXIES A  B  C  D  E  F  G  H  I  J  K  L  M  N  O  P  Q  R  S  T  U  V  W  X  Y  Z           HOME ABOUT CATEGORIES SITE MAP COPYRIGHT ADVERTISE CONTACT entire Web this site M101 (NGC 5457) M101 (the Pinwheel Galaxy) as imaged by the Spitzer Space Telescope in infrared light. Red regions mark zones depleted in polycyclic aromatic hydrocarbons M101 in visible light. Image: Hubble Space Telescope A very large, relatively nearby, face-on spiral galaxy, also known as the Pinwheel Galaxy, in the constellation Ursa Major. M101 was discovered by Pierre Méchain in 1781 and was among the first "spiral nebulae" identified by Lord Rosse. While appearing superficially symmetric on short exposures that show only the central region, it is actually remarkably unsymmetric, with a core considerably displaced from the center of the disk. Halton Arp included M101 as No. 26 in his Catalogue of Peculiar Galaxies with the description "Spiral with One Heavy Arm." It is the brightest of a group of at least nine galaxies, among which NGC 5474 (type Sc, magnitude 10.85) to the south-southeast and NGC 5585 (Sa, magnitude 11.49) to the northeast are the other most prominent. The M101 Group lies physically close to the larger M51 (NGC 5194) Group, and the two are often included together in lists as one large group. visual magnitude 7.9 apparent size 22' diameter 170,000 light-years distance 27 million light-years position R.A. 14h 03.2m, Dec. +54° 21' Related categories    • GALAXIES    • MESSIER CATALOGUE Also on this site: Encyclopedia of Alternative Energy & Sustainable Living Encyclopedia of History Transport Concepts & Designs (partner site) BACK TO TOP