NML Cygni

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NML Cygni or V1489 Cygni is a red hypergiant star,[1] and one of the largest stars known at present. It is about 1,650 times the Sun's radius. It is one of the extreme luminous supergiant stars.[2]

Its distance from Earth is estimated to be about 5,300 light-years.[2] This star has a dusty environment surrounding it, and it has a bean-shaped asymmetric nebula with H2O vapour.[3] It is a semiregular variable star with a period of about 940 days.[4]

NML Cygni is a part of the Cygnus OB2 association, which is 1.74 ± 0.2 kpc away. It is one of the closest massive associations to the Sun.[4]

It was discovered in 1965, by Neugebauer, Martz and Leighton.[5] The name NML comes from the names of these three discoverers.[6] It has also been given the designation V1489 on account of the small semi-regular brightness variations caused by pulsations and mass loss.

From the observations, this star has two dense envelopes of dust and molecules. The star has one of the largest mass loss rates at around 2 × 10-4 M per year.[5] These dust envelopes are formed by the high mass emission rate. Because of its unique position in the Milky Way, the star does not dominate its local interstellar environment.[4]

NML Cyg is a massive oxygen-rich star.[7] Molecules like H2O, SiO, CO, HCN, CS, SO, SO2 and H2S are also present.[5]

References[change | change source]

  1. Zhang, B.; Reid, M. J.; Menten, K. M.; Zheng, X. W.; Brunthaler, A. (2012). "The distance and size of the red hypergiant NML Cygni from VLBA and VLA astrometry". Astronomy & Astrophysics 544 (A42). doi:10.1051/0004-6361/201219587. 
  2. 2.0 2.1 Schuster M.T. (2007). Investigating the circumstellar environments of the cool hypergiants. ProQuest. p. 57. ISBN 978-0-549-32782-0. Retrieved 27 August 2012. 
  3. Schuster M.T; Humphreys R.M. & Marengo M. 2006. The circumstellar environments of NML Cygni and the cool hypergiants. The Astronomical Journal 131, 603. [1]
  4. 4.0 4.1 4.2 Schuster M.T. et al 2009. Imaging the cool hypergiant NML Cygni's dusty circumstellar envelope with adaptive optics. The Astrophysical Journal 699 (2): 1423. [2]
  5. 5.0 5.1 5.2 Marvel, Kevin (1996). "NML Cygni". The circumstellar environment of evolved stars as revealed by studies of circumstellar water masers. Universal-Publishers. pp. 182–212. ISBN 978-1-58112-061-5. Retrieved 23 August 2012. 
  6. Hearnshaw J.B. (1996). "New infrared sources and their interpretation". The measurement of starlight: two centuries of astronomical photometry. Cambridge University Press. p. 278. ISBN 978-0-521-40393-1. Retrieved 23 August 2012. 
  7. "Combined array for research in millimeter-wave astronomy" (PDF). Retrieved August 27, 2012.