m33 ngc 598 spiral triangulum galaxy in triangulum

The Triangulum Galaxy (also known as Messier 33 or NGC 598) is a spiral galaxy approximately 3 million light-years away in the constellation Triangulum. The galaxy is also sometimes informally referred to as the Pinwheel Galaxy by some amateur astronomy references[7] and in some public outreach websites.[8] However, the SIMBAD Astronomical Database, a professional astronomy database that contains formal designations for astronomical objects, indicates that the name "Pinwheel Galaxy" is used to refer to Messier 101,[9] and several other amateur astronomy resources and other public outreach websites also identify Messier 101 by that name.[10][11] With a diameter of about 50,000 light-years, it is the third largest galaxy in the Local Group, a group of galaxies which also contains the Milky Way Galaxy and the Andromeda Galaxy, and it may be a gravitationally bound companion of the Andromeda Galaxy. Estimates indicate that Triangulum may be home to between 30 and 40 billion stars,[12] compared to the 1000 billion stars for Andromeda and c. 200-400 billion for the Milky Way. The Pisces Dwarf (LGS 3), one of the small Local Group member galaxies, is possibly a satellite of Triangulum.