Deep Sky Directory
Clusters of Galaxies / Colliding Galaxies / Elliptical Galaxies / Local Group / Milky Way / Spiral Galaxies
Spiral Galaxy M33 (NGC 598), type Sc, in Triangulum
Right Ascension 01 : 33.9 (h:m)
Declination +30 : 39 (deg:m)
Distance 3000 (kly)
Visual Brightness 5.7 (mag)
Apparent Dimension 73x45 (arc min)
Probably discovered by Hodierna before 1654. Independently discovered by Charles Messier 1764.
The Triangulum galaxy M33 is another prominent member of the Local Group of galaxies. This galaxy is small compared to its big apparent neighbor, the Andromeda galaxy M31, and to our Milky Way galaxy, but by this more of average size for spiral galaxies in the universe. One of the small Local Group member galaxies, LGS 3, is possibly a satellite of M33, which itself may be a remote but gravitationally bound companion of the Andromeda galaxy M31.
M33 is approaching us (our Solar System) at 182 km/s according to R. Brent Tully, or at 179 +/-3 km/s according to NED. Corrected for our motion around the Milky Way's Galactic Center, it is approaching our Galaxy at 24 km/sec.
M33 was probably first found by Hodierna before 1654 (perhaps together with open cluster NGC 752). It was independently rediscovered by Charles Messier, and cataloged by him on August 25, 1764. Nevertheless, William Herschel, who otherwise carefully avoided to number Messier's objects in his survey, assigned it the number H V.17, on the ground of an observation dated September 11, 1784.