Edwin Hubble discovered the first Cepheid variable in this galaxy, proving that it was not a star cluster in the Milky Way.
This object once crashed into the Maffei I group, ejecting the latter from its group. Companions to this object include the Pegasus and Cassiopeia dwarves. The bright globular cluster G1, also known as Mayall II, is in this object. In 1991, this object was discovered to have a double nucleus. This object's apparent neighbor, the Triangulum galaxy, may be gravitationally bound to it. Edwin Hubble discovered the first Cepheid variable in this galaxy, proving that it was not a star cluster in the Milky Way. Named for and contained in a constellation including Sirrah, for 10 points, name this large member of the Local Group, the nearest spiral galaxy to the Milky Way.
This object once crashed into the Maffei I group, ejecting the latter from its group.
Andromeda galaxy [accept M31]