NGC 1978

NGC 1978
The globular cluster NGC 1978
Observation data (J2000 epoch)
ClassVI[1]
ConstellationDorado
Right ascension05h 28m 48s[2]
Declination−66° 13′ 59″[2]
Distance159,700 ly[3] (49,000 pc[3])
Apparent magnitude (V)10.12[4]
Apparent dimensions (V)10.7′ × 3.9′[3]
Physical characteristics
Mass2×105[5] M☉
Metallicity = −0.38 ± 0.02 dex
                 = 0.008[6] dex
Estimated age1.9 ± 0.1 Gyr[6]
Other designationsESO 85-SC90, KMHK 944
See also: Globular cluster, List of globular clusters

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

  1. ^ 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. ^ a b "Globular Cluster NGC 1978". DSO. Retrieved 15 October 2017.
  3. ^ a b c "The globular cluster NGC 1978". In the sky. Retrieved 22 October 2017.
  4. ^ a b c d 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. arXiv:2104.06882. doi:10.1093/mnras/stab1065.
  5. ^ a b 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. arXiv:1006.3121. Bibcode:2010MNRAS.408..522K. doi:10.1111/j.1365-2966.2010.17137.x. S2CID 118506707.
  6. ^ a b c 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. arXiv:astro-ph/0701649. Bibcode:2007AJ....133.2053M. doi:10.1086/513076. S2CID 17715270.
  7. ^ "NGC 1978 (in the Large Magellanic Cloud)". cseligman. Retrieved 16 October 2017.
  8. ^ "Object: NGC 1978 (*)". SEDS. Retrieved 16 October 2017.
  9. ^ a b c 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. arXiv:0906.1279. Bibcode:2009A&A...502..913L. doi:10.1051/0004-6361/200911857. S2CID 17017344.
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