NGC 147

NGC 147 is a Dwarf spheroidal galaxy in the constellation Cassiopeia. Along with its neighbor NGC 185, NGC 147 is a satellite galaxy of the Andromeda Galaxy, M 31.

Discovered by John Herschel on September 8, 1829, this galaxy was numbered h 29 by Herschel in his catalog of 1833, and GC 72 in his General Catalogue of 1864. Dreyer describes NGC 147 as "very faint, very large, irregularly round, gradually suddenly much brighter middle, star of 11th mag nearby."

NGC 147 has apparent dimensions of 15.0 x 9.4', and a visual magnitude of 9.5. Visually it is both fainter and slightly larger than NGC 185, but both galaxies are visible in small telescopes.

NGC 147 is a member of the Local group of galaxies, and a satellite galaxy of the Andromeda Galaxy (M 31). It forms a physical pair with the nearby galaxy NGC 185, another remote satellite of M 31. NGC 147 was recognized as a Local Group member galaxy by Walter Baade in 1944, when he resolved it into stars with the 100-inch reflector on Mt. Wilson.

NGC 147 is about 2.5 million light years away, and 10,500 light years across. The last significant star-forming activity in NGC 147 occurred around 3 billion years ago, and NGC 147 contains a large population of older stars.