Andromeda XXI

Andromeda XXI

Andromeda XXI, also called And 21 or And XXI, is a moderately bright dwarf spheroidal galaxy. It is about 859,000 to 920,000 light-years from the Sun in the constellation Andromeda. It is the fourth largest dwarf spheroidal galaxy in the Local Group of galaxies. This group includes our own Milky Way and the Andromeda Galaxy.

This galaxy was found using data from the first year of the Pan-Andromeda Archaeological Survey (PAndAS). The survey used the Megaprime/MegaCam wide-field camera on the Canada-France-Hawaii Telescope. It studied areas around the Andromeda Galaxy (M31) and the Triangulum Galaxy (M33).

Andromeda XXI is a satellite of the larger Andromeda Galaxy. It looks like a group of stars in space and does not have any new stars being born today. Most of its stars formed about 5.8 billion years ago. Scientists think it may have lost a lot of its mass long ago because of the pull of the Andromeda Galaxy.