The Local Group is the group of galaxies that includes Earth's galaxy, the Milky Way. The group comprises more than 54 galaxies (including dwarf galaxies), with its gravitational center located somewhere between the Milky Way and the Andromeda Galaxy. The galaxies of the Local Group cover a diameter of 10 megalight-years (3.1 megaparsecs) (see 1 E+22 m for distance comparisons) and have a binary (dumbbell) distribution. The group is estimated to have a total mass of 1.29±0.14 ×1012 M☉ and has a velocity dispersion of 61±8 km/s. The group itself is part of the Virgo Supercluster (i.e. the Local Supercluster).
The two most massive members of the group are the Milky Way and the Andromeda Galaxy. These two spiral galaxies each have a system of satellite galaxies.
- The Milky Way's satellite system consists of Sagittarius Dwarf Galaxy, Large Magellanic Cloud, Small Magellanic Cloud, Canis Major Dwarf, Ursa Minor Dwarf, Draco Dwarf, Carina Dwarf, Sextans Dwarf, Sculptor Dwarf, Fornax Dwarf, Leo I, Leo II, and Ursa Major I Dwarf and Ursa Major II Dwarf.
- Andromeda's satellite system comprises M32, M110, NGC 147, NGC 185, And I, And II, And III, And IV, And V, Pegasus dSph (aka And VI), Cassiopeia Dwarf (aka And VII), And VIII, And IX, And X, And XI, And XII, And XIII, And XIV, And XV, And XVI, And XVII, And XVIII, And XIX, and And XX.
- The Triangulum Galaxy, the third largest and only unbarred spiral galaxy in the Local Group, may or may not be a companion to the Andromeda Galaxy. Pisces Dwarf is equidistant from the Andromeda Galaxy and the Triangulum Galaxy, so it may be a satellite of either.
- The membership of NGC 3109, and its companions Sextans A and the Antlia Dwarf, is uncertain due to their extreme distance from the center of the Local Group.
The other members of the group are gravitationally secluded from these large subgroups: IC10, IC1613, Phoenix Dwarf, Leo A, Tucana Dwarf, Cetus Dwarf, Pegasus Dwarf Irregular, Wolf-Lundmark-Melotte, Aquarius Dwarf, and Sagittarius Dwarf Irregular.
Read more about Local Group: History, Other Notable Objects
Famous quotes containing the words local and/or group:
“While it may not heighten our sympathy, wit widens our horizons by its flashes, revealing remote hidden affiliations and drawing laughter from far afield; humor, in contrast, strikes up fellow feeling, and though it does not leap so much across time and space, enriches our insight into the universal in familiar things, lending it a local habitation and a name.”
—Marie Collins Swabey. Comic Laughter, ch. 5, Yale University Press (1961)
“...Women’s Studies can amount simply to compensatory history; too often they fail to challenge the intellectual and political structures that must be challenged if women as a group are ever to come into collective, nonexclusionary freedom.”
—Adrienne Rich (b. 1929)