NGC 1978 explained

NGC 1978
Epoch:J2000
Class:VI[1]
Constellation:Dorado
Ra:[2]
Dist Ly:159,700 ly
Dist Pc:49,000 pc
Appmag V:10.12
Size V:10.7 × 3.9[3]
Mass Msol:[4]
Metal Fe:−0.38 ± 0.02
Metal Z:0.008[5]
Age:1.9 ± 0.1 Gyr
Names: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.[6] 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. It appears 3.9 arcminutes wide.[7] NGC 1978 has a radial velocity of 293.1 ± 0.9 km/s.[8]

The northwest half of NGC 1978 is iron-rich and younger whereas the southeast part of the cluster has very little iron.[8] NGC 1978 is also highly elliptical (ε ~ 0.30 ± 0.02),[5] suggesting tidal action between it and the Large Magellanic Cloud.[8] It is rich in pulsating asymptotic giant branch stars, often oxygen-rich or carbon-rich.[4] NGC 1978 is about 2 billion years old. Its estimated mass is, and its total luminosity is, leading to a mass-to-luminosity ratio of 0.40 /.[9] All else equal, older star clusters have higher mass-to-luminosity ratios; that is, they have lower luminosities for the same mass.[9]

Notes and References

  1. 1995A&A...298..427B. NGC 1978 in the LMC: The cluster and surrounding field. Astronomy and Astrophysics. 298. 427. Bomans. D. J.. Vallenari. A. De Boer. K. S. 1995.
  2. Web site: Globular Cluster NGC 1978. DSO. 15 October 2017.
  3. Web site: The globular cluster NGC 1978. In the sky. 22 October 2017.
  4. 2010MNRAS.408..522K. 10.1111/j.1365-2966.2010.17137.x. 1006.3121. The pulsation of AGB stars in the Magellanic Cloud clusters NGC 1978 and 419. Monthly Notices of the Royal Astronomical Society. Kamath, D.. Wood, P. R.. Soszyński, I.. Lebzelter, T.. 408. 1. 522–534. October 2010. 118506707 .
  5. 2007AJ....133.2053M. The Globular Cluster NGC 1978 in the Large Magellanic Cloud. The Astronomical Journal. 133. 5. 2053–2060. May 2007. Mucciarelli, Alessio. Ferraro, Francesco R.. Origlia, Livia. Fusi Pecci, Flavio. astro-ph/0701649. 10.1086/513076. 17715270 .
  6. Web site: NGC 1978 (in the Large Magellanic Cloud). cseligman. 16 October 2017.
  7. Web site: Object: NGC 1978 (*). SEDS. 16 October 2017.
  8. 10.1051/0004-6361/200911857. 2009A&A...502..913L. 0906.1279. The puzzling dredge-up pattern in NGC 1978. Astronomy & Astrophysics. 502. 3. 913. 2009. Lederer. M. T. Lebzelter. T. Cristallo. S. Straniero. O. Hinkle. K. H. Aringer. B. 17017344 .
  9. 10.1093/mnras/stab1065. Dynamical masses and mass-to-light ratios of resolved massive star clusters – II. Results for 26 star clusters in the Magellanic Clouds. 2021. Song. Ying-Yi. Mateo. Mario. Bailey. John I.. Walker. Matthew G.. Roederer. Ian U.. Olszewski. Edward W.. Reiter. Megan. Kremin. Anthony. Monthly Notices of the Royal Astronomical Society. 504. 3. 4160–4191. 2104.06882.

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