Survey of Andromeda's satellite galaxies

This is a wide-angle view of the distribution of known satellite galaxies orbiting the large Andromeda galaxy (M31), located 2.5 million light-years away. The NASA/ESA Hubble Space Telescope was used to study the entire population of 36 mini-galaxies circled in yellow. Andromeda is the bright spindle-shaped object at the image center. All the dwarf galaxies seem to be confined to a plane, all orbiting in the same direction. The wide view is from ground-based photography. Hubble's optical stability, clarity, and efficiency made this ambitious survey possible. Hubble close up snapshots of four dwarf galaxies are on image right. The most prominent dwarf galaxy is M32 (NGC 221), a compact ellipsoidal galaxy that might be the remnant core of a larger galaxy that collided with Andromeda a few billion years ago.