Andromeda XVIII, discovered in 2008, is a dwarf spheroidal galaxy (has no rings, low luminosity, much dark matter, little gas or dust), which is a satellite of the Andromeda Galaxy (M31).

It is relatively isolated, being about 1.8 million light-years (579 kpc) away.

However, for an isolated dwarf galaxy it is also unusually quiescent.

However, alternative hypotheses are also possible for Andromeda XVIII.

[2] It was announced in 2010 that the orbiting galaxies lie close to a plane running through M31's center.