NGC 147
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| Galaxy | List of galaxies |
|---|---|
| Observation data (Epoch J2000.0) | |
| Constellation | Cassiopeia |
| Right ascension | 00h 33m 12.1s<ref name="ned" /> |
| Declination | +48° 30′ 32″<ref name="ned" /> |
| Redshift | -193 ± 3 km/s<ref name="ned" /> |
| Distance | 2.67 ± 0.18 Mly (870 ± 60 kpc)<ref name="tonryetal2001">J. L. Tonry, A. Dressler, J. P. Blakeslee, E. A. Ajhar, A. B. Fletcher, G. A. Luppino, M. R. Metzger, C. B. Moore (2001). "The SBF Survey of Galaxy Distances. IV. SBF Magnitudes, Colors, and Distances". Astrophysical Journal 546: 681-693.</ref> |
| Type | dSph/dE5<ref name="ned">NASA/IPAC Extragalactic Database. Results for NGC 147. Retrieved on 2006-11-02.</ref> |
| Apparent dimensions (V) | 13′.2 × 7′.8<ref name="ned" /> |
| Apparent magnitude (V) | +10.5<ref name="ned" /> |
| Notable features | satellite galaxy of M31 |
| Other designations | |
| | |
NGC 147 is a Dwarf spheroidal galaxy about 2.7 million light-years away in the constellation Cassiopeia. NGC 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, 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, but both galaxies are visible in small telescopes.
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 telescope at Mount Wilson near Los Angeles.
Contents |
[edit] Characteristics
A survey of the brightest asymptotic giant branch (AGB) stars in the area of radius 2′ from the center of NGC 147 shows that the last significant start-forming activity in NGC 147 occurred around 3 Gyr ago.<ref name="Davidge2005">Davidge, T. J. (2005). "The Evolved Stellar Content of NGC 147, NGC 185, and NGC 205". The Astronomical Journal 130 (5): 2087-2103.</ref> NGC 147 contains a large population of older stars which show a spread in metallicity and age. The metallicity spread suggests that NGC 147 has had chemical enrichment. However, H I has not been seen and the interstellar medium (ISM) mass upper limit is much lower than expected had the material which is emitted from evolving stars been kept in the galaxy. This implies depletion of the ISM.<ref name="Davidge2005" />
[edit] See also
[edit] External links
[edit] References
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