Local Group
The small galaxy cluster group comprising the Milky Way, Andromeda (M31), Triangulum (M33), and over 80 dwarf satellite galaxies.
Governing formula
Diameter ~ 3 Mpc (~10 million ly), Mass ~ 2 × 10¹² M_☉
SI unit
Megaparsecs (Mpc)
In depth
Gravitationally bound system dominated in mass by the Milky Way and Andromeda galaxies. Andromeda and the Milky Way are approaching each other at ~110 km/s and will merge in ~4.5 billion years.
Examples in the real world
The Large and Small Magellanic Clouds orbiting the Milky Way as dwarf satellite galaxies within the Local Group.