M81 Group

The M81 Group is a galaxy group in the constellations Ursa Major and Camelopardalis that includes the galaxies Messier 81 and Messier 82, as well as several other galaxies with high apparent brightnesses.<ref name="karachentsev2005">Template:Cite journal</ref> 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.<ref name="karachentsev2005" /> The group is estimated to have a total mass of (1.03 ± 0.17)Template:ETemplate:Solar mass.<ref name="Karachentsevetal2006">Template:Cite journal</ref> The M81 Group, the Local Group, and other nearby groups all lie within the Virgo Supercluster (i.e. the Local Supercluster).<ref name="tully1982">Template:Cite journal</ref>

Members

Template:More references needed The table below lists galaxies that have been identified as associated with the M81 Group by I. D. Karachentsev.<ref name="karachentsev2005" />

Members of the M81 Group

Name	Type<ref name="ned">{{#invoke:citation/CS1|citation	CitationClass=web }}</ref>	R.A. (J2000)<ref name="ned" />	Dec. (J2000)<ref name="ned" />	Redshift (km/s)<ref name="ned" />	Apparent Magnitude<ref name="ned" />
Arp's LoopTemplate:Cn		Template:RA	Template:DEC	99	16.1
DDO 78Template:Cn	Im	Template:RA	Template:DEC	55 ± 10	15.8
F8D1Template:Cn	dE	Template:RA	Template:DEC		13.9
FM1Template:Cn	dSph	Template:RA	Template:DEC		17.5
HIJASS J1021+6842Template:Cn		Template:RA	Template:DEC	46	20
HS 117Template:Cn	I	Template:RA	Template:DEC	-37	16.5
Holmberg ITemplate:Cn	IAB(s)m	Template:RA	Template:DEC	139 ± 0	13.0
Holmberg II	Im	Template:RA	Template:DEC	142 ± 1	11.1
Holmberg IX	Im	Template:RA	Template:DEC	46 ± 6	14.3
IC 2574	SAB(s)m	Template:RA	Template:DEC	57 ± 2	13.2
IKN		Template:RA	Template:DEC		17.0
KKH 57	dSph	Template:RA	Template:DEC		18.5
Messier 81	SA(s)ab	Template:RA	Template:DEC	-34 ± 4	6.9
Messier 81 Dwarf A	I	Template:RA	Template:DEC	113 ± 0	16.5
Messier 82	I0	Template:RA	Template:DEC	203 ± 4	9.3
NGC 2366	IB(s)m	Template:RA	Template:DEC	80 ± 1	11.4
NGC 2403	SAB(s)cd	Template:RA	Template:DEC	131 ± 3	8.9
NGC 2976	SAc pec	Template:RA	Template:DEC	3 ± 5	10.8
NGC 3077	I0 pec	Template:RA	Template:DEC	14 ± 4	10.6
NGC 4236	SB(s)dm	Template:RA	Template:DEC	0 ± 4	10.1
PGC 28529	Im	Template:RA	Template:DEC	-40	17.1
PGC 28731	dE	Template:RA	Template:DEC	-135 ± 30	15.6
PGC 29231	dE	Template:RA	Template:DEC		16.7
PGC 31286	dSph	Template:RA	Template:DEC		16.7
PGC 32667	Im	Template:RA	Template:DEC	116 ± 1	14.9
UGC 4459	Im	Template:RA	Template:DEC	20 ± 0	14.5
UGC 4483		Template:RA	Template:DEC	156 ± 0	15.1
UGC 5428	Im	Template:RA	Template:DEC	-129 ± 0	18
UGC 5442	Im	Template:RA	Template:DEC	-18 ± 14	18
UGC 5692	Sm	Template:RA	Template:DEC	56 ± 3	13.5
UGC 6456	Pec	Template:RA	Template:DEC	-103 ± 0	14.5
UGC 7242	Scd	Template:RA	Template:DEC	68 ± 2	14.6
UGC 8201	Im	Template:RA	Template:DEC	31 ± 0	12.8
UGCA 133	dSph	Template:RA	Template:DEC		15.6

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.<ref name="yunetal1994">Template:Cite journal</ref> Observations of the 21-centimeter hydrogen line indicate how the galaxies are connected.<ref name="chynowethetal2008">Template:Cite journal</ref> The gravitational interactions have stripped some hydrogen gas away from all three galaxies, leading to the formation of filamentary gas structures within the group.<ref name="yunetal1994" /> Bridges of neutral hydrogen have been shown to connect M81 with M82 and NGC 3077.<ref name="chynowethetal2008" /><ref name="hulst1978">Template:Cite journal</ref> 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.<ref name="yunetal1994" /> Computer simulations of tidal interactions have been used to show how the current structure of the group could have been created.<ref name="yun1999">Template:Cite book</ref>

Gallery

• The mysteries of UGC 8201.jpg

  CitationClass=web }}</ref>

• M81+M82-and other galaxies.jpg

  Amateur picture Messier 81 + 82 and NGC 3077 all of the M81 group, 33 frames stacked of 1 minute each.

• M81m82 galex f.jpg

  The spiral galaxies Messier 81 and 82 and the dwarf galaxy Holmberg IX from GALEX

• M81 wide Galex.jpg

  Close up view of Messier 81 from GALEX

• Messier81 highres.jpg

  The spiral galaxy Messier 81 from Spitzer Space Telescope

• Ssc2003-06c.jpg

  The spiral galaxy Messier 81 from Spitzer Space Telescope

• M82 HST ACS 2006-14-a-large web.jpg

  Starburst galaxy Messier 82 from Hubble Space Telescope

• NGC2403 3.6 5.8 8.0 microns spitzer.png

  NGC 2403 in mid-infrared view, combining the 3.6, 5.8 and 8.0 μm bands of the Spitzer Space Telescope

• NGC2403 3.6 8.0 24 microns spitzer.png

  NGC 2403 in Mid-infrared view, combining the 3.6, 8.0 and 24 μm bands of the Spitzer Space Telescope

• NGC 2403HST.jpg

  NGC 2403 from Hubble Space Telescope

• NGC 2403HSTSN.jpg

  NGC 2403 from Hubble Space Telescope illustrated

• Galaxy-NGC-2403-with-SN2004DJ.jpeg

  Supernova SN2004DJ in the spiral galaxy NGC 2403

• NGC2403-SN2004dj.jpg

  Supernova 2004dj in NGC 2403

• NGC 4236 I FUV g2006.jpg

  NGC 4236 from GALEX

• NGC 2366HST.jpg

  NGC 2366 from Hubble Space Telescope

• NGC 2976SSTFull.jpg

  Galaxy NGC 2976 from Spitzer Space Telescope in infrared

• NGC2976.jpg

  Galaxy NGC 2976 from an amateur Astronomer

• NGC 4605 GALEX WikiSky.jpg

  Galaxy NGC 4605 from GALEX

• Ngc2363HST.jpg

  NGC 2363 from Hubble Space Telescope

• NGC 2537 I FUV g2006.jpeg

  NGC 2537 from GALEX

• Holmberg IISST.jpg

  Holmberg II from Spitzer Space Telescope in infrared

• M81DwarBSST.jpg

  UGC 5423 / M81 dwarf B from Spitzer Space Telescope in infrared

• NGC 3077 2MASS.jpg

  NGC 3077 from 2MASS

• IC 2574 Hubble WikiSky.jpg

  IC 2574

See also

• UGC 5497

External links

• M81 Group @ SEDS
• M81 Group from An Atlas of The Universe