Astronomy: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 | [math]\displaystyle{ \begin{smallmatrix}\left[\ce{Fe}/\ce{H}\right]\end{smallmatrix} }[/math] = −0.38 ± 0.02 dex |
| Template:M/H 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 or open 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
- ↑ Bomans, D. J.; Vallenari, A; De Boer, K. S (1995). "NGC 1978 in the LMC: The cluster and surrounding field". Astronomy and Astrophysics 298: 427. Bibcode: 1995A&A...298..427B.
- ↑ 2.0 2.1 "Globular Cluster NGC 1978". DSO. https://dso-browser.com/deep-sky/2903/ngc-1978/globular-cluster.
- ↑ 3.0 3.1 3.2 "The globular cluster NGC 1978". In the sky. https://in-the-sky.org/data/object.php?id=1909.
- ↑ 4.0 4.1 4.2 4.3 Song, Ying-Yi; Mateo, Mario; Bailey, John I.; Walker, Matthew G.; Roederer, Ian U.; Olszewski, Edward W.; Reiter, Megan; Kremin, Anthony (2021). "Dynamical masses and mass-to-light ratios of resolved massive star clusters – II. Results for 26 star clusters in the Magellanic Clouds". Monthly Notices of the Royal Astronomical Society 504 (3): 4160–4191. doi:10.1093/mnras/stab1065.
- ↑ 5.0 5.1 Kamath, D.; Wood, P. R.; Soszyński, I.; Lebzelter, T. (October 2010). "The pulsation of AGB stars in the Magellanic Cloud clusters NGC 1978 and 419". Monthly Notices of the Royal Astronomical Society 408 (1): 522–534. doi:10.1111/j.1365-2966.2010.17137.x. Bibcode: 2010MNRAS.408..522K.
- ↑ 6.0 6.1 6.2 Mucciarelli, Alessio; Ferraro, Francesco R.; Origlia, Livia; Fusi Pecci, Flavio (May 2007). "The Globular Cluster NGC 1978 in the Large Magellanic Cloud". The Astronomical Journal 133 (5): 2053–2060. doi:10.1086/513076. Bibcode: 2007AJ....133.2053M.
- ↑ "NGC 1978 (in the Large Magellanic Cloud)". cseligman. http://cseligman.com/text/atlas/ngc19a.htm#1978.
- ↑ "Object: NGC 1978 (*)". SEDS. http://spider.seds.org/ngc/revngcic.cgi?ngc1978.
- ↑ 9.0 9.1 9.2 Lederer, M. T; Lebzelter, T; Cristallo, S; Straniero, O; Hinkle, K. H; Aringer, B (2009). "The puzzling dredge-up pattern in NGC 1978". Astronomy & Astrophysics 502 (3): 913. doi:10.1051/0004-6361/200911857. Bibcode: 2009A&A...502..913L.
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