Life isn't easy for a dwarf galaxy in our local group. They're passed from galaxy to galaxy, harassed by gravity, and eventually torn up and consumed when they get to close to a large galaxy like our own Milky Way. But astronomers have turned up an example of a new class of dwarf galaxy, ones which formed very far away, and just arrived at the party.
The new dwarf galaxy is called Andromeda XII, and it was discovered during a wide-field survey taken with the Canada-France Hawaii Telescope's "MegaCam" instrument. It's one of the faintest dwarf galaxies ever discovered near the Andromeda galaxy (M31), and it probably has the lowest mass ever measured.
Instead of being one of these dwarf galaxies that's suffered billions of years of galactic harassment, Andromeda XII is on a fast moving, highly eccentric orbit, which means it's falling into the Local Group of galaxies for the first time. And since it lived its life apart from these galactic interactions, it's a pristine object to study. Its rate of star formation, the size and shape of its dark matter halo and evolution weren't influenced by other galaxies.
Andromeda XII is moving so quickly that it probably won't even be captured by the Local Group, passing right through to destinations unknown.
Original Source: W.M. Keck Observatory News Releasehttp://www.universetoday.com/2007/05/29/dwarf-galaxy-is-falling-into-our-local-group-for-the-first-time/