Which constellation contains the Triangulum Galaxy, Messier 33?

The Triangulum Galaxy, Messier 33, lies in the constellation Triangulum.

Triangulum is a small northern constellation named for the long, narrow triangle formed by its principal stars. Its most famous deep-sky object is M33, a spiral galaxy and one of the three major members of the Local Group, alongside the Milky Way and the Andromeda Galaxy. The galaxy’s name comes directly from its constellation setting.

The Italian astronomer Giovanni Battista Hodierna probably recorded M33 before 1654. Charles Messier independently catalogued it on 25–26 August 1764, giving it the familiar designation Messier 33. Under exceptionally dark skies, its diffuse glow can sometimes be detected with the unaided eye, although light pollution makes it difficult even in binoculars.

M33 is often confused with Andromeda because both are nearby Local Group galaxies, and it may have interacted gravitationally with Andromeda. However, the galaxy is within Triangulum’s official boundaries, near the constellation’s border with Pisces. Triangulum also contains the quasar 3C 48, an important object in radio-astronomy history.