Pismis 20 is a compact open cluster in Circinus. It is located at the heart of the Circinus OB1 association in the Norma arm of the Milky Way Galaxy.[2] Pismis 20 is about 3,270 pc away and only about 5 million years old. HD 134959, a blue supergiant variable star also called CX Circinus, is the brightest star in Pismis 20.[3]

Pismis 20
Observation data (J2000 epoch)
Right ascension15h 15m 23.0s[1]
Declination−59° 04′ 00″[1]
Distance3,270 pc
Physical characteristics
Estimated age5×106 years
Other designationsVDBH 170, MWSC 2281, C 1511-588, OCl 932
Associations
ConstellationCircinus
See also: Open cluster, List of open clusters
Prominent stars
Star name MV number Effective temperature Absolute magnitude Bolometric magnitude Mass (M) Spectral type Ref.
WR 67 11 56000 -4.03 -8 9 WN6-w [4]
CX Circinus (HD 134959) 1 20900 -7.9 -9.8 50 B2.5Ia [5]
6 42600 -4.2 -8.2 34 B [5]
2 34400 -5.4 -8.8 34 O8.5I [5]
3 28800 -5.5 -8.4 26 B0I [5]
7 30200 -5 -8 23 B0III [5]
4 29500 -5 -7.9 23 B0.2III [5]
5 30200 -4.5 -7.5 20 B0III [5]

References

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  1. ^ a b "Pismis 20". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 30 December 2020.
  2. ^ Turner, David G. (1996). "PISMIS 20 - A Case Study of a Young Cluster". Astronomical Journal. 111: 828. Bibcode:1996AJ....111..828T. doi:10.1086/117829.
  3. ^ Orsatti, A. M.; Vega, E. I.; Marraco, H. G. (2003). "Pismis 20: One or two clusters?". Astronomy and Astrophysics. 408: 135–140. Bibcode:2003A&A...408..135O. doi:10.1051/0004-6361:20030919. hdl:11336/36974 – via 2003A&A...408..135O.
  4. ^ Sota, A.; Maíz Apellániz, J.; Morrell, N. I.; Barbá, R. H.; Walborn, N. R.; Gamen, R. C.; Arias, J. I.; Alfaro, E. J.; Oskinova, L. M. (2019). "The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters". Astronomy & Astrophysics. A57: 625. arXiv:1904.04687. Bibcode:2019A&A...625A..57H. doi:10.1051/0004-6361/201834850. S2CID 104292503.
  5. ^ a b c d e f g Massey, P.; Degioia-Eastwood, K.; Waterhouse, E. (2001). "The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turnoffs. II. Results from 12 Galactic Clusters and OB Associations". The Astronomical Journal. 121 (2): 1050–1070. arXiv:astro-ph/0010654. Bibcode:2001AJ....121.1050M. doi:10.1086/318769. S2CID 53345173.