HV 11423

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HV 11423
Small Magellanic Cloud (Digitized Sky Survey 2).jpg
HV 11423 is visible in the full-size image, just to the left (south is up) of cluster NGC 361 (below centre, between the two bright foreground stars). (Digitized Sky Survey 2)
Observation data
Epoch J2000      Equinox J2000
Constellation Tucana
Right ascension 01h 00m 55.20s[1]
Declination −71° 37′ 52.9″[1]
Apparent magnitude (V) 11.84 - 12.46[2]
Evolutionary stage Red supergiant
Spectral type M0 Iab[3] (K0/1 I - M4.5/5 I[4])
B−V color index +1.88 - +1.95[2]
Variable type Lc[5]
Radial velocity (Rv)108.268[6] km/s
Distance~200,000[citation needed] ly
Absolute magnitude (MV)−6.5 - −8.4[4]
December 2004
Radius960-1,060 R
Diameter960-1,060 D
Luminosity350,000 L
Surface gravity (log g)−0.2 cgs
Temperature4,300-4,480 K
December 2005
Radius1,000-1,220 R
Luminosity200,000 L
Surface gravity (log g)−0.4 cgs
Temperature3,500-3,635 K
Other designations
PMMR 114, LI-SMC 140, 2MASS J01005519-7137529
Database references

HV 11423 (PMMR 114 or 140 LI-SMC) is a red supergiant star in the Small Magellanic Cloud. It is about 200,000 light-years away towards the constellation of Tucana.[citation needed]


The spectral type of HV 11423 is variable, from K0-1I in December 2004, to M4I in December 2005, and back to K0-1I by September 2006. Very Large Telescope file spectra show that in December 2001 the star was even cooler (M4-5I). By contrast, in October 1978 and a year later, it appeared as a star of class M0I. The spectral type M4-5 is the latest observed in a supergiant of the Small Magellanic Cloud[4]


HV 11423 is one of largest known stars with an estimated radius over 1,000 times bigger than the sun. It is also a variable star with a variation of up 2 magnitudes at visual wavelengths but essentially constant in the infrared. It is listed in the General Catalogue of Variable Stars as a slow irregular variable, but a period of 720 days has been calculated, as well as a long secondary period of 1,817 days.[7]

The bolometric luminosity is over 300,000 times more than Sun, making it one of most luminous cool supergiants, and appears to have remained unchanged during the brightness and spectral variations. It is thought that the star is currently undergoing a period of intense instability, in which its effective temperature changes from 4,300 to 3,300 K in a time scale of months; V-band variability may be due primarily to variations in temperature as well as changes in the local extinction due to the creation and dissipation of circumstellar dust. It is speculated that the star may be nearing the end of its life.[4]


  1. 1.0 1.1 Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A.; Carpenter, J. M.; Chester, T.; Cambresy, L.; Evans, T. et al. (2003). "VizieR Online Data Catalog: 2MASS All-Sky Catalog of Point Sources (Cutri+ 2003)". VizieR On-line Data Catalog: II/246. Originally published in: 2003yCat.2246....0C 2246. Bibcode 2003yCat.2246....0C.
  2. 2.0 2.1 Levesque, E. M.; Massey, P.; Olsen, K. A. G.; Plez, B. (2009). "The Coolest Stars in the Clouds: Unusual Red Supergiants in the Magellanic Clouds". The Biggest 412: 33. Bibcode 2009ASPC..412...33L.
  3. Humphreys, R. M. (1979). "M supergiants and the low metal abundances in the Small Magellanic Cloud". Astrophysical Journal 231: 384. Bibcode 1979ApJ...231..384H. doi:10.1086/157201.
  4. 4.0 4.1 4.2 4.3 4.4 Massey, Philip; Levesque, Emily M.; Olsen, K. A. G.; Plez, Bertrand; Skiff, B. A. (2007). "HV 11423: The Coolest Supergiant in the SMC". The Astrophysical Journal 660: 301. arXiv:astro-ph/0701769. Bibcode 2007ApJ...660..301M. doi:10.1086/513182.
  5. Samus, N. N.Expression error: Unrecognized word "etal". (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S 1. Bibcode 2009yCat....102025S.
  6. Kordopatis, G.; Gilmore, G.; Steinmetz, M.; Boeche, C.; Seabroke, G. M.; Siebert, A.; Zwitter, T.; Binney, J. et al. (2013). "The Radial Velocity Experiment (RAVE): Fourth Data Release". The Astronomical Journal 146 (5): 134. arXiv:1309.4284. Bibcode 2013AJ....146..134K. doi:10.1088/0004-6256/146/5/134.
  7. Yang, Ming; Jiang, B. W. (2012). "The Period-Luminosity Relation of Red Supergiant Stars in the Small Magellanic Cloud". The Astrophysical Journal 754: 35. arXiv:1205.1275. Bibcode 2012ApJ...754...35Y. doi:10.1088/0004-637X/754/1/35.

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