Messier 81

From Wikipedia, the free encyclopedia

**Messier 81**
Observation data (Epoch J2000)
Galaxy	List of galaxies
M81
Constellation	Ursa Major
Right ascension	09^h 55^m 33.2^s^[1]
Declination	+69° 3′ 55″^[1]
Redshift	-34 ± 4 km/s^[1]
Distance	11.8 ± 1.1 Mly (3.6 ± 0.3 Mpc)^[2]
Type	SA(s)ab^[1]
Apparent dimensions (V)	26′.9 × 14′.1^[1]
Apparent magnitude (V)	+7.9^[1]
Notable features
Other designations
NGC 3031,^[1] UGC 5318,^[1] PGC 28630,^[1] Bode's Galaxy^[3]

Messier 81 (also known as NGC 3031 or Bode's Galaxy) is a spiral galaxy about 12 million light-years away in the constellation Ursa Major. It was first discovered by Johann Elert Bode in 1774 and was nicknamed Bode's Galaxy in his honour. In 1993, a supernova (SN 1993J) of was observed in M81.

M81 is believed to contain approximately 250 billion stars, making it slightly smaller than our own Milky Way Galaxy. It is one of the most striking examples of a grand design spiral galaxy, with near perfect arms spiraling into the very center.

M81 and M82 are the most prominent members of the M81 Group with M81 being about twice as massive as M82 which is estimated to be only 54%^[2] of the mass of M81.

M81 has an apparent magnitude of +7.9, making it one of the brightest galaxies that can be seen from the Earth. While compact objects of such magnitudes are visible to the naked eye under ideal conditions [1], the diffuse nature of M81 renders it too faint to see unaided, and thus cannot claim the title for furthest naked-eye object (which is usually taken to be M33)

Multiwavelength infrared observations of M81 by the Spitzer Space Telescope. The blue colors trace starlight in the 3.6 micrometre wave band. The green colors trace polycyclic aromatic hydrocarbon emission in the 8.0 micrometre wave band. The red colors trace hot dust emission in the 24 micrometre wave band.