NGC 147
Galaxy in the constellation Cassiopeia / From Wikipedia, the free encyclopedia
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NGC 147 (also known as DDO3 or Caldwell 17) is a dwarf spheroidal galaxy about 2.58 Mly away in the constellation Cassiopeia. NGC 147 is a member of the Local group of galaxies and a satellite galaxy of the Andromeda Galaxy (M31). It forms a physical pair with the nearby galaxy NGC 185,[5] another remote satellite of M31. It was discovered by John Herschel in September 1829. Visually it is both fainter and slightly larger than NGC 185 (and therefore has a considerably lower surface brightness). This means that NGC 147 is more difficult to see than NGC 185, which is visible in small telescopes. In the Webb Society Deep-Sky Observer's Handbook,[6] the visual appearance of NGC 147 is described as follows:
Large, quite faint, irregularly round; it brightens in the middle to a stellar nucleus.
NGC 147 | |
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Observation data (J2000 epoch) | |
Constellation | Cassiopeia |
Right ascension | 00h 33m 12.1s[1] |
Declination | +48° 30′ 32″[1] |
Redshift | -193 ± 3 km/s[1] |
Distance | 2.53 ± 0.11 Mly (780 ± 30 kpc)[2][3][4][a] |
Apparent magnitude (V) | 10.5[1] |
Characteristics | |
Type | dSph/dE5[1] |
Apparent size (V) | 13.2′ × 7.8′[1] |
Notable features | satellite galaxy of M31 |
Other designations | |
PGC 2004,[1] UGC 326,[1] DDO 3,[1] LEDA 2004, Caldwell 17 |
The membership of NGC 147 in the Local Group was confirmed by Walter Baade in 1944 when he was able to resolve the galaxy into individual stars with the 100-inch (2.5 m) telescope at Mount Wilson near Los Angeles.