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. Because of its proximity to Earth, its large size, and its active galactic nucleus (which harbors a 70 million M☉ supermassive black hole), Messier 81 is a popular galaxy to study in professional astronomy research. The galaxy’s large size and relatively low apparent magnitude (lower magnitude implies higher brightness) also make it a popular target for amateur astronomy observations.
Messier 81 is the largest galaxy in the M81 Group, a group of 34 galaxies located in the constellation Ursa Major. The distance from the Earth to the group is approximately 11.7 Mly (3.6 Mpc), making this one of the closest groups to the Local Group, which contains the Milky Way.
M81 is gravitationally interacting with Messier 82 and NGC 3077. The interactions have stripped some hydrogen gas away from all three galaxies, leading to the formation of filamentary gas structures in the group. Moreover, the interactions have also caused some interstellar gas to fall into the centers of Messier 82 and NGC 3077, which has led to strong starburst activity (or the formation of many stars) within the centers of these two galaxies.