NGC 7331
NGC 7331, also known as Caldwell 30, is an unbarred spiral galaxy in the constellation Pegasus. It sits about 43 million light-years away (roughly 13.4 megaparsecs) from Earth and was discovered by William Herschel on September 6, 1784.
It’s sometimes called the Milky Way’s twin because of its similar size and shape, but newer findings suggest the Milky Way may be a barred spiral, so the comparison isn’t exact. In NGC 7331, the central bulge rotates in the opposite direction to the rest of the disk, and the core appears slightly off-center in images, with one side of the disk extending farther from the core than the other.
NGC 7331 is the brightest galaxy in its small group, known as the NGC 7331 Group (Holm 795). Other group members (NGC 7335, 7336, 7337, and 7340) lie much farther away, about 300–350 million light-years behind. The Holm 795 designation comes from Erik Holmberg’s 1937 study of double and multiple galaxies.
The galaxy has an apparent magnitude of about 10.4 and spans roughly 10 by 4 arcminutes on the sky. Its redshift is about 0.00272, corresponding to a radial velocity of around 816 km/s. Four supernovae have been observed in NGC 7331.
This page was last edited on 2 February 2026, at 12:42 (CET).