Cassiopeia Dwarf (Cas dSph)
A recently-discovered dwarf spheroidal
galaxy that is also a satellite
galaxy of the Andromeda Galaxy (M31),
and hence also a member of the Local Group.
The Cassiopaeia Dwarf, also known as Andromeda VII, was found in 1998 in
the constellation Cassiopeia, together with
another small satellite of M31, the Pegasus
Dwarf (Peg dSph), by a team of astronomers in Russia and the Ukraine.
At a distance of 2.6 million light-years from the Sun, Cas dSph and Peg
dSph are farther from Andromeda than its other known companion galaxies,
yet still appear bound to it by gravity. Neither galaxy contains any young,
massive stars or shows traces of recent star
formation. Instead, both seem dominated by very old stars, with ages
up to 10 billion years.