The M81 Group is a galaxy group in the constellationsUrsa Major and Camelopardalis that includes the galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses.[1] The approximate center of the group is located at a distance of 3.6 Mpc, making it one of the nearest groups to the Local Group.[1] The group is estimated to have a total mass of (1.03 ± 0.17)×1012M☉.[2]
The M81 Group, the Local Group, and other nearby groups all lie within the Virgo Supercluster (i.e. the Local Supercluster).[3]
Note that the object names used in the above table differ from the names used by Karachentsev. NGC, IC, UGC, and PGC numbers have been used in many cases to allow for easier referencing.
Interactions within the group
Messier 81, Messier 82, and NGC 3077 are all strongly interacting with each other.[5] Observations of the 21-centimeter hydrogen line indicate how the galaxies are connected.[6]
The gravitational interactions have stripped some hydrogen gas away from all three galaxies, leading to the formation of filamentary gas structures within the group.[5] Bridges of neutral hydrogen have been shown to connect M81 with M82 and NGC 3077.[6][7] 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.[5] Computer simulations of tidal interactions have been used to show how the current structure of the group could have been created.[8]
Gallery
Galaxy UGC 8201 is a dwarf irregular galaxy member of the M81 galaxy group.[9]
Amateur picture Messier 81 + 82 and NGC 3077 all of the M81 group, 33 frames stacked of 1 minute each.
The spiral galaxies Messier 81 and 82 and the dwarf galaxy Holmberg IX from GALEX
Close up view of Messier 81 from GALEX
The spiral galaxy Messier 81 from Spitzer Space Telescope
The spiral galaxy Messier 81 from Spitzer Space Telescope
Starburst galaxy Messier 82 from Hubble Space Telescope
NGC 2403 in mid-infrared view, combining the 3.6, 5.8 and 8.0 μm bands of the Spitzer Space Telescope
NGC 2403 in Mid-infrared view, combining the 3.6, 8.0 and 24 μm bands of the Spitzer Space Telescope
NGC 2403 from Hubble Space Telescope
NGC 2403 from Hubble Space Telescope illustrated
Supernova SN2004DJ in the spiral galaxy NGC 2403
Supernova 2004dj in NGC 2403
NGC 4236 from GALEX
NGC 2366 from Hubble Space Telescope
Galaxy NGC 2976 from Spitzer Space Telescope in infrared
Galaxy NGC 2976 from an amateur Astronomer
Galaxy NGC 4605 from GALEX
NGC 2363 from Hubble Space Telescope
NGC 2537 from GALEX
Holmberg II from Spitzer Space Telescope in infrared
UGC 5423 / M81 dwarf B from Spitzer Space Telescope in infrared
↑Hulst, J. M. van der (1978). "The Structure and Kinematics of the Neutral Hydrogen Bridge Between M 81 and NGC 3077". Astronomy and Astrophysics. 75 (1–2): 97–111.
