Pismis 20

Pismis 20
Observation data (J2000 epoch)
Right ascension	15^h 15^m 23.0^s[1]
Declination	−59° 04′ 00″[1]
Distance	3,270 pc
Physical characteristics
Estimated age	5×10^6 years
Other designations	VDBH 170, MWSC 2281, C 1511-588, OCl 932
Associations
Constellation	Circinus

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]

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

1. "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. 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.