The Local Group is a collection of more than 40 galaxies, spread across a volume of space some
10 million light-years in diameter, of which our own Milky
Way Galaxy and the Andromeda Galaxy are the dominant and central members. Both these two giant spirals have
retinues of satellite galaxies,
which together account for most of the membership of the Local Group.
The Milky Way's satellites include: the Large Magellanic
Cloud, the Small Magellanic Cloud, the Sagittarius
Dwarf Elliptical, the Ursa Minor
Dwarf, the Draco Dwarf, the Carina
Dwarf, the Sextans Dwarf, the Sculptor Dwarf, the Fornax
Dwarf, Leo I, and Leo
II. Among the retinue of the Andromeda Galaxy are: M32 , M110, the fainter and more faraway NGCs 147
and 185, the very faint systems And I, And II, And III, and possibly And
IV, And V, And VI (the Pegasus Dwarf),
and And VII (the Cassiopeia Dwarf).
The third-largest galaxy, the Triangulum
Galaxy (M33), may or may not be an outlying gravitationally-bound companion
of M31, but has itself probably the dwarf LGS 3 as a satellite. The other
members of the Local Group, including the Antlia
Dwarf and Wolf-Lundmark-Melotte Galaxy,
fall outside the main subgroups and float alone in the gravitational seas
between the giant group members.
The substructures of the group are probably not stable. Observations and
calculations suggest that the group is highly dynamic and has changed significantly
in the past. The galaxies around the large elliptical Maffei 1 (see Maffei
1 Group, for example, were probably once part of our galaxy group. Indeed,
the Local Group is not isolated but is in gravitational interaction and
member exchange with the nearest surrounding groups, notably the Maffei
1 Group, the Sculptor Group, the M81 Group, and the M83 Group. In the future,
interaction between the member galaxies and with the cosmic neighborhood
will continue to change the Local Group. Some astronomers speculate that
the two large spirals, our Milky Way and the Andromeda Galaxy, may collide
and merge to form a giant elliptical. Also, there is evidence that our nearest
big cluster of galaxies, the Virgo Cluster,
will probably stop our cosmological recession away from it, accelerate the
Local Group toward itself, and so eventually assimilate the Local Group
into its collection.
galaxy
RA
Dec
type
abs
mag
diameter
(ly)
rad vel
(km/s)
distance
(ly)
Milky Way Galaxy
17:45.6
-28:56
SBbc I-II
-20.6
90,000
0
28,000
Sagittarius Dwarf Elliptical
18:55
-30:30
dSph(E7)
-14.0
10,000
78,000
Large Magellanic Cloud
05:19.7
-68:57
Irr III-IV
-18.1
30,000
+119
179,000
Small Magellanic Cloud
00:51.7
-73:14
Irr IV-V
-16.2
16,000
+34
210,000
Ursa Minor Dwarf
15:08.8
+67:12
dSph
-8.9
2,000
-47
215,000
Sculptor Dwarf
01:00.0
-33:42
dSph
-10.7
3,000
+115
260,000
Draco Dwarf
17:20.1
+57:55
dSph
-8.6
3,000
-87
270,000
Sextans Dwarf
10:13.2
-01:37
dSph
-10.0
4,000
280,000
Carina Dwarf
06:14.6
-50:58
dSph
-9.92
2,000
+13
330,000
Fornax Dwarf
02:39.9
-34:32
dSph
-13.0
6,000
-41
450,000
Leo II
11:13.5
+22:10
dSph
-10.2
3,000
+36
670,000
Leo I
10:08.5
+12:18
dE3
-12.0
3,000
+60
820,000
Phoenix Dwarf
01:51.1
-44:27
dIrr/dSph
-9.9
2,000
1,450,000
NGC 6822 (Barnard's Galaxy)
19:44.9
-14:49
Irr IV-V
-16.4
8,000
+44
1,600,000
Andromeda II
01:16.4
+33:27
dSph
-11.7
2,000
1,700,000
NGC 185
00:39.0
+84:20
dSph/dE3
-15.3
8,000
+39
2,000,000
Leo III (Leo A)
09:59.4
+30:45
dIrr
-11.7
4,000
-19
2,250,000
Andromeda VII
23:27.8
+50:35
dSph
-12.0
2,000
2,250,000
IC 1613
01:05.1
+02:08
Irr V
-14.9
10,000
-152
2,300,000
NGC 147
00:33.2
+48:31
dSph/dE5
-14.8
10,000
+28
2,350,000
Andromeda III
00:35.4
+36:31
dSph
-10.2
3,000
2,500,000
Cetus Dwarf
00:26.1
-11:02
dSph
-10.1
3,000
2,550,000
Andromeda VI
23:51.7
+24:36
dSph
-11.3
3,000
2,550,000
Aquarius Dwarf
20:46.8
-12:51
dIrr/dSph 2
-23
2,600,000
M32
00:42.7
+40:52
dE2
-16.4
8,000
-28
2,600,000
Andromeda I
00:45.7
+38:00
dSph
-11.7
2,000
2,600,000
Andromeda V
01:10.3
+47:38
dSph
-9.1
2,650,000
LGS 3 (Pisces Dwarf)
01:03.8
+21:53
dIrr/dSph
-9.7
2,000
-149
2,650,000
Andromeda Galaxy (M31)
00:42.7
+41:16
Sb I-II
-21.1
140,000
-121
2,650,000
M110 (NGC 205)
00:41.3
+41:41
dSph/dE5
-16.3
15,000
-60
2,650,000
IC 10
00:20.4
+59:18
dIrr
-17.6
8,000
-146
2,700,000
Triangulum Galaxy (M33)
01:33.9
+30:39
Sc II-III
-18.9
55,000
-46
2,850,000
Tucana Dwarf
22:41.7
-64:25
dSph
-9.6
2,000
2,850,000
Wolf-Lundmark-Mellote
00:02.0
-15:28
Irr IV-V
-14.0
10,000
-61
3,000,000
Pegasus Dwarf
23:28.6
+14:45
dIrr/dSph
-12.7
2,000
-20
3,100,000
Sagittarius Dwarf Irregular
19:30.1
-17:42
dIrr
-11.0
3,000
+8
3,450,000
Antlia Dwarf
10:04.1
-27:20
dSph
-10.7
3,000
4,000,000
NGC 3109
10:03.1
-26:09
Irr IV-V
-15.8
25,000
+194
4,100,000
UGC-A92
04:27.4
+63:30
dIrr
3,000
+66
4,200,000
UKS 2323-326
23:26.5
-32:23
dIrr
-13.1
3,000
+74
4,300,000
Sextans B
10:00.0
+05:20
dIrr
-14.4
8,000
+168
4,400,000
Sextans A
10:11.1
-04:43
dIrr
-14.3
10,000
+164
4,700,000
IC 5152
22:06.1
-51:17
dIrr
8,000
+80
5,200,000
GR 8
12:58.7
+14:13
dIrr
-12.5
2,000
+183
5,200,000