C17
NGC 147
Elliptical
Properties
Position & Identifiers
Visibility
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About C17
Description
NGC 147 is a dwarf spheroidal galaxy in Cassiopeia, about 2.5 million light-years away. It is a satellite of the Andromeda Galaxy (M31) and forms a pair with its neighbor NGC 185 (C18). The galaxy has virtually no gas, dust, or recent star formation.
Observing Tips
A faint, diffuse smudge requiring at least a 6-inch telescope and dark skies. It has very low surface brightness. Use low power and averted vision. Located about 1 degree from NGC 185 and both can be seen in the same wide field. Best in autumn.
History
Discovered by John Herschel in 1829. It was one of the first dwarf galaxies recognized as a satellite of M31, helping astronomers understand the hierarchical structure of galaxy groups.
Fun Facts
NGC 147 stopped forming stars about 3 billion years ago, making it a "dead" galaxy. Despite being a satellite of Andromeda, it lies about 660,000 light-years from M31's center.
Community Photos (1)
Credit: NASA Hubble Space Telescope. License: CC BY 2.0. (Wikimedia Commons)
Skybred Mar 2, 2026