M81 group

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The galaxies M81 (below) and M82 (above) that form the core of the M81 group, captured by the Galaxy Evolution Explorer . Slightly to the left of M81 is the dwarf galaxy Holmberg IX , a satellite galaxy of M81.

The M81 group is a group of galaxies that is in close proximity to the Local Group . In addition to the Milky Way , the local group also includes the Andromeda Galaxy . The best-known members of the M81 group are the two galaxies Messier 81 (M81), from which the name is derived, and Messier 82 (M82). In total, around 60 galaxies belong to this group, with seven large galaxies among them.

Discovery story

The first members of the M81 group were already known towards the end of the 18th century. The group's two best-known galaxies, M81 and M82, were discovered on December 31, 1774 by the German astronomer Johann Elert Bode . Irrespective of this, both galaxies were found in August 1779 by Pierre Méchain , who had them included in his catalog by Charles Messier . All NGC objects in the M81 group were sighted and cataloged by Wilhelm Herschel between 1788 and 1801 .

morphology

The location of the M81 group within the neighborhood of the local group

The M81 group extends over the constellations Great Bear and Giraffe and has an angular extent of about 40 ° × 20 °, which corresponds to about 1.8 × 0.9 megaparsecs or 5.87 × 2.93 million light years .

The distance from our sun to the center of the galaxy cluster is about 12 million light years . This makes the M81 group of our local group the second closest galaxy cluster. A little closer are parts of the Sculptor group , a galaxy cluster whose center is also about 12 million light years away.

The M81 group and the local group belong with some other galaxy groups to the Virgo supercluster , the center of which is the Virgo galaxy cluster . Due to the small redshift of the members of the M81 group, it can be assumed that the M81 group, like the local group, is moving towards the center of the Virgo galaxy cluster. The center of the M81 group is formed by the galaxies M81, M82 and NGC 3077, as well as a few other spiral and irregular dwarf galaxies .

The mass of visible matter including the calculated mass of dark matter is (1.6 ± 0.3) · 10 12  M ☉ .

Galaxies in the M81 group

Members of the M81 group
Surname Other
names 		Type Rect. ( J2000.0 ) Dec. ( J2000.0 ) Distance
to the sun
(million ly ) 		Helligk.
m 		Red
shift
( km / s ) 		Apparent
diameter 		Absolute
diameter
light years 		Mass [ M ☉ ]
M81 NGC 3031 SA (s) from 09h55m33s + 69 ° 03'55 " 11.84 +6.9 −34 ± 4 26.9 '× 14.1' 95,000
NGC 2403 SAB (s) cd 07h36m51s + 65 ° 36'09 " 10.76 +8.93 131 ± 3 21.9 'x 12.3' 75,000
NGC 4236 SB (s) dm 12h16m42s + 69 ° 27'45 " 14.51 +10.05 0 ± 4 21.9 'x 7.2' 75,000
IC 2574 SAB (s) m 10h28m23s + 68 ° 24'44 " 13.11 +10.8 57 ± 2 13.2 'x 5.4' 45,000
M82 NGC 3034 I0 09h55m52s + 69 ° 40'47 " 11.51 +9.3 203 ± 4 11.2 '× 4.3' 40,000
NGC 2366 IB (s) m 07h28m55s + 69 ° 12'57 " 10.40 +10.91 80 ± 1 8.1 '× 3.3' 30,000
UGC 4305 Holmberg II in the 08h19m05s + 70 ° 43'12 " 11.06 +11.1 142 ± 1 7.9 '× 6.3' 30,000
NGC 2976 SAc 09h47m15s + 67 ° 54'59 " 11.61 +10.82 3 ± 5 5.9 'x 2.7' 20,000
NGC 3077 I0 10h03m19s + 68 ° 44'02 " 12.46 +10.61 14 ± 4 5.4 'x 4.5' 20,000
NGC 4605 SB (s) c 12h39m59s + 61 ° 36'33 " 16.96 +10.1 143 ± 5 5.8 'x 2.2' 20,000
UGC 5139 Holmberg I. IAB (s) m 09h40m32s + 71 ° 10'56 " 12.52 +13 139 ± 0 3.6 '× 3' 15,000 5.5 · 10 8
NGC 5204 SA (s) w 13h29m37s + 58 ° 25'07 " 14.51 +11.73 201 ± 1 5 '× 3' 15,000
NGC 3738 Insane 11h35m49s + 54 ° 31'26 " 15.49 +12.13 229 ± 4 2.5 'x 1.9' 10,000
UGC 5336 Holmberg IX in the 09h57m32s + 69 ° 02'45 " 12.06 +14.3 46 ± 6 2.5 '× 2' 10,000
UGC 5692 DDO 82 Sm 10h30m35s + 70 ° 37'07 " 13.05 +13.47 56 ± 3 3.2 '× 1.8' 10,000
UGC 5918 DDO 87 in the 10h49m37s + 65 ° 31'50 " 24.14 +15.1 340 ± 1 2.4 '× 2.4' 10,000
UGC 8201 DDO 165 in the 13h06m25s + 67 ° 42'25 " 14.91 +12.8 31 ± 0 3.5 '× 1.9' 10,000
UGCA 133 DDO 44 in the 07h34m11s + 66 ° 53'10 " 10.40 +15.64 3 '× 2' 10,000
PGC 23521 M81 dwarf A, KDG 52 I. 08h23m56s + 71 ° 01'45 " 11.58 +16.5 133 ± 0 1.3 '× 0.7' 5,000
PGC 30664 DDO 78 in the 10h26m27s + 67 ° 39'16 " 12.13 +15.8 55 ± 10 2 '× 2' 5,000
UGC 3794 Sm 07h22m51s + 77 ° 48'23 " +16.5 2656 ± 4 1.5 '× 1.3' 5,000
UGC 4459 DDO 53 in the 08h34m07s + 66 ° 10'54 " 11.61 +14.48 20 ± 0 1.5 '× 1.3' 5,000
UGC 4483 BCG 08h37m03s + 69 ° 46'31 " 10.47 +15.12 156 ± 0 1.4 'x 0.7' 5,000
UGC 4945 UGCA 158 in the 09h22m25s + 75 ° 45'57 " 17.29 +17 659 ± 1 1.3 '× 1.1' 5,000
UGC 5423 M81 dwarf B in the 10h05m31s + 70 ° 21'52 " +15.19 347 ± 1 0.9 '× 0.6' 5,000
UGC 5428 DDO 71 in the 10h05m06s + 66 ° 33'32 " 11.42 +18 −129 ± 0 0.9 '× 0.9' 5,000
UGC 5442 KDG 64 in the 10h07m02s + 67 ° 49'39 " 12.07 +18 −18 ± 14 1.8 'x 0.9' 5,000
UGC 6456 11h27m60s + 78 ° 59'39 " 14.16 +14.5 −103 ± 0 1.4 '× 0.8' 5,000
UGCA 220 in the 10h49m23s + 64 ° 43'20 " +16.9 1.7 'x 1.2' 5,000
UGCA 105 in the 05h14m15s + 62 ° 34'48 " 10.63 +13.9 111 ± 5 5.5 '× 3.5'
NGC 4144 SAB (s) cd 12h09m59s + 46 ° 27'26 " 31.96 +12.05 265 ± 1 6 '× 1.3'
Cam A Insane 04h25m16s + 72 ° 48'21 " 12.33 +14.84 −46 ± 1 3.7 '× 2.1'
IKN 10h08m06s + 68 ° 23'57 " 12.09 +17 2.7 '× 2.3'
NGC 4068 IC 757 I am 12h04m01s + 52 ° 35'18 " 17.29 +13 210 ± 3 3.3 '× 1.7'
F8D1 dE 09h44m47s + 67 ° 26'19 " 12.3 +13.85 2.2 '× 2'
KK 77 dSph 09h50m11s + 67 ° 30'24 " 11.35 +16.2 2.4 '× 1.8'
PGC 28759 Arp's Loop, A0952 09h57m33s + 69 ° 17'00 " 12.62 +16.08 99 ± 0 1.8 '× 1.6'
NGC 2537 SB (s) w 08h13m15s + 45 ° 59'23 " 22.51 +12.32 431 ± 1 1.7 'x 1.5'
Cam B Insane 04h53m07s + 67 ° 05'57 " 10.8 +16.1 77 ± 0 2.2 '× 1.1'
UGC 4426 DDO 52 in the 08h28m28s + 41 ° 51'24 " 18.59 +15 397 ± 4 2 '× 1'
UGC 8508 I am 13h30m44s + 54 ° 54'36 " 8.35 +14.4 62 ± 5 1.7 '× 1'
UGC 7242 Scd 12h14m08s + 66 ° 05'41 " 14.03 +14.6 68 ± 2 1.9 'x 0.8'
UGC 6541 Insane 11h33m29s + 49 ° 14'14 " 12.92 +14.5 250 ± 1 1.2 '× 0.7'
HS 117 Ir 10h21m25s + 71 ° 06'51 " 12.07 +16.5 −37 ± 0 1.5 'x 0.9'
PGC 28731 KDG 61 dE 09h57m03s + 68 ° 35'31 " 11.74 +15.6 −135 ± 30 1.2 '× 1'
VKN 08h40m09s + 68 ° 26'23 " 11.09 +17.7 0.9 '× 0.9'
PGC 31286 BK6N dSph 10h34m30s + 66 ° 01'00 " 12.56 +16.7 1 '× 0.8'
UGC 7298 in the 12h16m30s + 52 ° 13'39 " 13.6 +15 173 ± 0 1.3 '× 0.6'
FM1 dSph 09h45m10s + 68 ° 45'54 " 11.15 +17.5 0.9 '× 0.8'
PGC 29231 BK5N dE 10h04m41s + 68 ° 15'22 " 12.33 +16.72 0.8 '× 0.6'
UGCA 281 Sm 12h26m16s + 48 ° 29'37 " 18.59 +15.15 281 ± 4 0.8 '× 0.6'
KKH 34 Mailyan 13 Ir 05h59m40s + 73 ° 25'40 " 16.9 +17.1 110 ± 0 0.6 '× 0.5'
KKH 57 Sph 10h00m16s + 63 ° 11'06 " 12.82 +18.5 0.6 '× 0.5'
KK 109 dIrr 11h47m12s + 43 ° 40'18 " 15.33 +17.5 212 ± 1 0.6 '× 0.4'
KKH 87 Ir 14h15m09s + 57 ° 05'15 " 22.18 +16.5 320 ± 1 0.8 '× 0.3'
PGC 28529 BK3N in the 09h53m49s + 68 ° 58'08 " 13.11 +17.1 −40 ± 0 0.5 '× 0.4'
PGC 32667 KDG 73 in the 10h52m57s + 69 ° 32'58 " 12.07 +14.9 116 ± 1 0.6 '× 0.4'
KKH 79 Ir 12h19m52s + 61 ° 31'11 " 20.87 +17.5 516 ± 1 0.44 'x 0.2'
PGC 29167 Garland in the 10h03m42s + 68 ° 41'36 " 50 ± 0
HIJASS J1021 + 6842 HI 10h21m00s + 68 ° 42'00 " 12.07 +20 46 ± 0

The table is compiled from the information from Atlas of the Universe and The M81 group of Galaxies: New distances, kinematics and structure (2002) . The data for the type, the coordinates, brightness and the apparent diameter are taken from the NASA / IPAC Extragalactic Database . The data can be called up in the NED database using the designations in the Name column (exceptions: KK = KK98, HS = HS98, FM = FM2000). The distances are from Karachentsev's work in 2005 and 2002.

See also

Web links

Commons : M81 group  - album with pictures, videos and audio files

Individual evidence

  1. ↑ NASA / IPAC Extragalactic Database