Pismis 24-1

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Pismis 24-1
EmissionNebula NGC6357.jpg
Pismis 24-1 is the brightest point of light above the centre of this Hubble Space Telescope picture
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius
Right ascension 17h 24m 43.41s
Declination –34° 11′ 56.5″
Apparent magnitude (V) 10.43
Spectral type O3.5If*/O4III[1]
Variable type None
Absolute magnitude (MV) −6.3[1]
Mass 74 + 66[1] M
Radius 18 + 17 R
Luminosity 776,000 + 646,000[1] L
Temperature ~40,000[1] K
Age .724 million years
Database references

Pismis 24-1 (also known as HDE 319718) is part of the open cluster Pismis 24 within the nebula NGC 6357 about 8150 light-years away. Pismis 24-1 is the largest and more brilliant of the visible stars of this cluster, and is one of the most massive and luminous stars known. Pismis 24-1 is composed of at least three objects, the resolved Pismis 24-1SW and the unresolved spectroscopic binary Pismis 24-1NE.

The combined Pismis 24-1NE is slightly more luminous and hotter than 24-1SW, but is likely to consist of two similar objects both less luminous. This is surprising given the spectral luminosity classes and it could be that the interaction between the components of 24-1NE is confusing its classification.

When originally discovered and thought to be a single star, Pismis 24-1 was calculated to have a mass around 300 times the sun, but it is now known that the component stars are each of near 100 solar masses, making them among the more massive stars on record.[2]


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  1. ^ a b c d e Fang, M.; Van Boekel, R.; King, R. R.; Henning, T.; Bouwman, J.; Doi, Y.; Okamoto, Y. K.; Roccatagliata, V.; Sicilia-Aguilar, A. (2012). "Star formation and disk properties in Pismis 24". Astronomy & Astrophysics 539: A119. arXiv:1201.0833. Bibcode:2012A&A...539A.119F. doi:10.1051/0004-6361/201015914. 
  2. ^ NASA: Massive Stars in Open Cluster Pismis 24, 2006