|Designation|| Messier 51|
|Right ascension||13h 29m 52.7s|
|Declination||+47° 11′ 43″|
|Type of object||Spiral galaxy|
|Dimensions||11.2 x 6.9'|
|Magnitude|| Apparent Mag: +8.4|
|Distance from Earth||23±4 million light years|
|Radial velocity||463±3 km/s|
The Whirlpool galaxy (M51, NGC 5194) is a spiral galaxy in the constellation of Canes Venatici. it is one of the most spectacular galaxies known and one of the easiest to find. It is sometimes called the "Question mark galaxy." The larger galaxy is catalogued as NGC 5194 in the New General catalogue while the smaller galaxy is NGC 5195. Messier 51 can refer to NGC 5194 or both galaxies, though it usually is just NGC 5194. Sometimes NGC 5194 is also called M51a and NGC 5195 is called M51b. It was the first spiral galaxy ever discovered.
The larger galaxy, NGC 5194 was discovered Charles Messier in 1773 while he was attempting to observe a comet. The smaller galaxy was discovered later in 1781 by Messier's colleague, Pierre Méchain. Messier was not able to identify any [star]]s stating the object was a, "very faint nebula without stars." It was not until 1845 that William Parsons' Leviathan, a 72 inch reflecting telescope identified a spiral structure, the first observed. Wlliam Parsons was the 3rd Earl of Rosse, giving another name form the object of "Rosse's galaxy."
Environment and Structure
The Whirlpool galaxy has a diameter of 60,000 light years and an estimated mass of 160 billion solar masses. This is around 35% the size of the Milky Way. The distance across both galaxies is about 75,000 light years. The smaller galaxy, NGC 5195 is a dwarf galaxy and classified as an irregular galaxy.