View source for Pismis 20

{{Infobox cluster|name=Pismis 20|image=Pis20.jpg|credit=|class=Open Cluster|epoch=[[J2000]]|ra={{RA|15|15|23.0}}<ref name="simbad">{{cite simbad |title=Pismis 20 |access-date=30 December 2020}}</ref>|dec={{DEC|-59|04|00}}<ref name="simbad" />|dist_ly=3,270 pc|size_v=|radius_ly=|absmag_v=7.8|constellation=[[Circinus]]|age={{val|5|e=6|u=years}}|notes=|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 [[OB association|association]] in the [[Norma arm]] of the [[Milky Way]] Galaxy.<ref>{{Cite journal|last=Turner|first=David G.|date=1996|title=PISMIS 20 - A Case Study of a Young Cluster|journal=Astronomical Journal|volume=111|pages=828|bibcode=1996AJ....111..828T|doi=10.1086/117829|doi-access=free}}</ref> Pismis 20 is about {{val|3,270|ul=pc|fmt=commas}} 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.<ref>{{Cite journal|last1=Orsatti|first1=A. M.|last2=Vega|first2=E. I.|last3=Marraco|first3=H. G.|date=2003|title=Pismis 20: One or two clusters?|journal=Astronomy and Astrophysics|volume=408|pages=135–140|doi=10.1051/0004-6361:20030919|bibcode=2003A&A...408..135O|via=2003A&A...408..135O|doi-access=free|hdl=11336/36974|hdl-access=free}}</ref>

{| class="wikitable sortable"
|+Prominent stars
!Star name
!MV number
!Effective temperature
!Absolute magnitude
!Bolometric magnitude
!Mass ({{solar mass|link=yes}})
!Spectral type
!Ref.
|-
|WR 67
|11
|56000
| -4.03
| -8
|9
|WN6-w
|<ref name=hamann2019>{{cite journal|arxiv=1904.04687|last1=Sota|first1=A.|title=The Galactic WN stars revisited. Impact of Gaia distances on fundamental stellar parameters|last2=Maíz Apellániz|first2=J.|last3=Morrell|first3=N. I.|author-link3=Nidia Morrell|last4=Barbá|first4=R. H.|last5=Walborn|first5=N. R.|last6=Gamen|first6=R. C.|last7=Arias|first7=J. I.|last8=Alfaro|first8=E. J.|last9=Oskinova|first9=L. M.|journal=Astronomy & Astrophysics|year=2019|volume=A57|page=625|doi=10.1051/0004-6361/201834850|bibcode=2019A&A...625A..57H|s2cid=104292503}}</ref>
|-
|CX Circinus (HD 134959)
|1
|20900
| -7.9
| -9.8
|50
|B2.5Ia
|<ref name="Massey" />
|-
|
|6
|42600
| -4.2
| -8.2
|34
|B
|<ref name="Massey" />
|-
|
|2
|34400
| -5.4
| -8.8
|34
|O8.5I
|<ref name="Massey">{{cite journal|author1=Massey, P.|author2=Degioia-Eastwood, K.|author2-link=Kathy Eastwood|author3=Waterhouse, E.|date=2001|title=The Progenitor Masses of Wolf-Rayet Stars and Luminous Blue Variables Determined from Cluster Turnoffs. II. Results from 12 Galactic Clusters and OB Associations|journal=The Astronomical Journal|volume=121|issue=2|pages=1050–1070|arxiv=astro-ph/0010654|bibcode=2001AJ....121.1050M|doi=10.1086/318769|s2cid=53345173}}</ref>
|-
|
|3
|28800
| -5.5
| -8.4
|26
|B0I
|<ref name="Massey" />
|-
|
|7
|30200
| -5
| -8
|23
|B0III
|<ref name="Massey" />
|-
|
|4
|29500
| -5
| -7.9
|23
|B0.2III
|<ref name="Massey" />
|-
|
|5
|30200
| -4.5
| -7.5
|20
|B0III
|<ref name="Massey" />
|-
|}

== References ==
{{reflist}}

{{Sky|15|15|23.0|-|59|04|00|100000000000}}

{{Stars of Circinus}}

[[Category:Open clusters]]
[[Category:Circinus]]
[[Category:Star-forming regions]]

{{star-cluster-stub}}