Pismis 20 Explained

Pismis 20
Class:	Open Cluster
Epoch:	J2000
Ra:	^[1]
Dist Ly:	3,270 pc
Absmag V:	7.8
Constellation:	Circinus
Names:	VDBH 170, MWSC 2281, C 1511-588, OCl 932

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 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 !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
	6	42600	-4.2	-8.2	34	B
	2	34400	-5.4	-8.8	34	O8.5I	^[5]
	3	28800	-5.5	-8.4	26	B0I
	7	30200	-5	-8	23	B0III
	4	29500	-5	-7.9	23	B0.2III
	5	30200	-4.5	-7.5	20	B0III

Notes and References

1. Pismis 20 . 30 December 2020.
2. Turner. David G.. 1996. PISMIS 20 - A Case Study of a Young Cluster. Astronomical Journal. 111. 828. 1996AJ....111..828T. 10.1086/117829. free.
3. Orsatti. A. M.. Vega. E. I.. Marraco. H. G.. 2003. Pismis 20: One or two clusters?. Astronomy and Astrophysics. 408. 135–140. 10.1051/0004-6361:20030919. 2003A&A...408..135O. 2003A&A...408..135O. free. 11336/36974. free.
4. 1904.04687. Sota. A.. The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters. Maíz Apellániz. J.. Morrell. N. I.. Nidia Morrell. Barbá. R. H.. Walborn. N. R.. Gamen. R. C.. Arias. J. I.. Alfaro. E. J.. Oskinova. L. M.. Astronomy & Astrophysics. 2019. A57. 625. 10.1051/0004-6361/201834850. 2019A&A...625A..57H. 104292503.
5. Massey, P.. Degioia-Eastwood, K.. Kathy Eastwood. 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. astro-ph/0010654. 2001AJ....121.1050M. 10.1086/318769. 53345173.