NGC 1978
| NGC 1978 | |
|---|---|
 The globular cluster NGC 1978 | |
| Observation data (J2000 epoch) | |
| Class | VI[1] |
| Constellation | Dorado |
| Right ascension | 05h 28m 48s[2] |
| Declination | −66° 13′ 59″[2] |
| Distance | 159,700 ly[3] (49,000 pc[3]) |
| Apparent magnitude (V) | 10.12[4] |
| Apparent dimensions (V) | 10.7′ × 3.9′[3] |
| Physical characteristics | |
| Mass | 2×105[5] M☉ |
| Metallicity | [Fe/H] = −0.38 ± 0.02 dex |
| = 0.008[6] dex | |
| Estimated age | 1.9 ± 0.1 Gyr[6] |
| Other designations | ESO 85-SC90, KMHK 944 |
NGC 1978 (also known as ESO 85-SC90) is an elliptical shaped globular cluster in the constellation Dorado. It is located within the Large Magellanic Cloud. It was discovered by James Dunlop on November 6, 1826.[7] At an aperture of 50 arcseconds, its apparent V-band magnitude is 10.20, but at this wavelength, it has 0.16 magnitudes of interstellar extinction.[4] It appears 3.9 arcminutes wide.[8] NGC 1978 has a radial velocity of 293.1 ± 0.9 km/s.[9]
The northwest half of NGC 1978 is iron-rich and younger whereas the southeast part of the cluster has very little iron.[9] NGC 1978 is also highly elliptical (ε ~ 0.30 ± 0.02),[6] suggesting tidal action between it and the Large Magellanic Cloud.[9] It is rich in pulsating asymptotic giant branch stars, often oxygen-rich or carbon-rich.[5] NGC 1978 is about 2 billion years old. Its estimated mass is 1.36×105 M☉, and its total luminosity is 3.41×105 L☉, leading to a mass-to-luminosity ratio of 0.40 M☉/L☉.[4] All else equal, older star clusters have higher mass-to-luminosity ratios; that is, they have lower luminosities for the same mass.[4]
References
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External links
[edit | edit source]- Error creating thumbnail: File missing Media related to Lua error in Module:Commons_link at line 62: attempt to index field 'wikibase' (a nil value). at Wikimedia Commons
