The M81 group is another famous group of galaxies mainly because it contains the famous M81/M82 pair of galaxies discovered in 1784. NGC 2403 is another prominantspiral galaxy on the right side of the group. M82 is a famous example of astarburst galaxy - there is a lot of star formation occuring in this galaxy.
Below - three galaxies in the right side of the M81 group. NGC 2366 (left)is an irregular galaxy where a lot of recent star formation has occured. Thebrightest part of this galaxy is known as NGC 2363 - it is a huge HII region(emission nebula) where a lot of bright blue stars have formed. NGC 2403 (centre)is the second largest galaxy in the M81 group.Holmberg II (right) is oneof nine low-surface-brightness galaxies listed by Erik Holmberg in the 1950's,three of which are associated with the M81 group.
 |  |  |
| NGC 2366 | NGC 2403 | Holmberg II |
This is a list of the main galaxies in the M81 group. The three maingalaxies in this group are M81, NGC 2403 and NGC 4236.
1 2 3 4 5 6 7 8 9Name Equatorial Blue Type Size Size RV Other Coordinates Mag (') kly km/s Names RA DecUGC 3794 07 22.9 +77 48 17.8 SBm 1.0 5 ? NGC 2366 07 28.9 +69 12 11.9 Irr 8.1 30 134UGCA 133 07 34.2 +66 53 15.9 E 3.0 10 ? DDO 44NGC 2403 07 36.8 +65 36 8.9 SBc 21.9 75 181Holmberg II 08 19.1 +70 43 11.1 Irr 7.9 30 207 UGC 4305M81dwA 08 23.2 +71 02 16.5 Irr 1.8 5 163 PGC 23521UGC 4459 08 34.2 +66 11 15.0 Irr 1.5 5 95 DDO 53UGC 4483 08 37.1 +69 47 15.5 Irr 1.1 5 217UGC 4945 08 55.9 +72 01 17? E 1.3 5 700 UGCA 158Holmberg I 09 40.5 +71 11 13.2 Irr 3.6 15 208 UGC 5139NGC 2976 09 47.3 +67 55 10.9 Sc 5.9 20 94M81 09 55.6 +69 04 7.9 Sab 26.9 95 50 NGC 3031M82 09 55.8 +69 41 9.2 Irr 11.2 40 296 NGC 3034Holmberg IX 09 57.7 +69 03 14.4 Irr 2.5 10 134 UGC 5336NGC 3077 10 03.4 +68 44 10.6 Irr 5.4 20 102UGC 5428 10 05.1 +66 33 16.0 E 0.9 5 -22 DDO 71UGC 5423 10 05.5 +70 22 15.9 Irr 0.9 5 424 M81dwBUGC 5442 10 07.1 +67 49 15.4 E 1.8 5 78DDO 78 10 26.5 +67 40 15.8 E 2.0 5 ? PGC 30664IC 2574 10 28.4 +68 25 10.8 SBm 13.2 45 142UGC 5692 10 30.6 +70 37 13.5 Sm 3.2 10 262 DDO 82UGCA 220 10 49.3 +64 43 16.9 Irr 1.7 5 ? UGC 5918 10 49.6 +65 32 15.1 Irr 2.4 10 452 DDO 87UGC 6456 11 28.0 +78 59 15.9 Irr 1.4 5 -61NGC 3738 11 35.8 +54 31 12.1 Irr 2.5 10 406NGC 4236 12 16.8 +69 28 10.1 SBd 21.9 75 87NGC 4605 12 40.0 +61 37 10.9 SBc 5.8 20 272UGC 8201 13 06.5 +67 42 12.9 Irr 3.5 10 121 DDO 165NGC 5204 13 29.6 +58 26 11.7 Sm 5.0 15 329 |
Column 1: The usual name of the galaxy.Column 2: The Right Ascension for epoch 2000.Column 3: The Declination for epoch 2000.Column 4: The blue apparent magnitude of the galaxy.Column 5: The galaxy type: E=Elliptical, S0=Lenticular, Sa,Sb,Sc,Sd=Spiral, SBa,SBb,SBc,SBd=Barred Spiral, Sm,SBm,Irr=Irregular.Column 6: The angular diameter of the galaxy (arcminutes).Column 7: The diameter of the galaxy (thousands of light years).Column 8: The recessional velocity (km/s) of the galaxy relative to the cosmic microwave background.Column 9: Other names of the galaxy.References:Karachentsev I, Dolphin A, Geisler D, Grebel E, Guhathakurta P, Hodge P, Karachentseva V, Sarajedini A, Seitzer P, Sharina M, (2002), The M 81 group of galaxies: New distances, kinematics and structure. Astron and Astrophys, 383, 125.van Driel W, Kraan-Korteweg R, Binggeli B, Huchtmeier W, (1998), An HI line search for optically identified dwarf galaxy candidates in the M 81 group. Astron and Astrophys Supp, 127, 397.Schmidt K, Priebe A, Boller T, (1993), Nearby Galaxies. Astron Nachr, 314, 371.The HyperLeda Database, (2003).
Below - three more M81 group galaxies. M82 (left) is a very famous exampleof a starburst galaxy - it contains a lot of young, bright stars probably becausea close encounter with its more massive neighbour M81 has triggered a lot of newstar formation. IC 2574 (centre) by contrast is a much dimmer galaxy even thoughit is approximately the same size as M82. NGC 4236 (right) is a large galaxy inthe left side of the M81 group.
 |  |  |
| M82 | IC 2574 | NGC 4236 |
Shown below is M81. This galaxy is the dominant galaxy in the group and itis similar in size to the Milky Way. This galaxy is one of the brightest galaxiesin the sky, and although it is too faint to see with the naked eye, it is aneasy galaxy to find with binoculars if you know where to look.
Below - three bright dwarf galaxies in the M81 group. NGC 2976 (left) is asmall spiral galaxy approximately two million light years behind M81.NGC 3077 (centre) is much closer to M81 - they are separated by about 140 thousandlight years. NGC 4605 (right) is a small spiral galaxy on the left edge ofthe group.
 |  |  |
| NGC 2976 | NGC 3077 | NGC 4605 |
| Properties of the M81 Group | |
|---|---|
| Equatorial Coordinates | RA=10h00m Dec=+68° |
| Galactic Coordinates | l=145° b=+40° |
| Supergalactic Coordinates | L=40° B=0° |
| Distance to the centre of the group | 12 million light years |
| Number of large galaxies | 7 |
