M 81

M81 is one of the easiest and most rewarding galaxies for the amateur astronomer on the northern hemisphere, especially as it forms a most conspicuous physical pair with its neighbor, M82, and is the brightest and probably dominant galaxy of a nearby group called M81 group. The semi-recent close encounter which has dramatically deformed M82 has also left traces in the spiral pattern of this brighter and larger galaxy, first making it overall more pronounced, and second in the form of th dark linear feature in the lower left of the nuclear region.

Using the Hubble Space Telescope, a team under Wendy Freedman of the Carnegie Institution of Washington has investigated 32 Cepheid variables in M81 and determined the distance to be 11.0 million light years, in 1993 well before the HST was refurbished.

In 1993, a supernova (1993J) occured in M81. The remnant of this supernova was imaged in the radio light at 3.6 cm wavelength roughly eight month after the explosion.

M81 has been found to probably have only little dark matter in 1994, when its rotation curve was found to fall off in the outer regions.

Ultraviolet image from the ASTRO-1 mission.
Visible image, also from ASTRO-1
More images of M81

Right ascension	09 : 51.5 (hours : minutes)
Declination	+69 : 18 (degrees : minutes)
Distance	7000.0 (light-years*10^3)
Visual magnitude	7.9