View source for NGC 2204

{{Short description|Open cluster in the constellation Canis Major}}
{{Use dmy dates|date=January 2024}}
{{Infobox open cluster
 | name      = NGC 2204
 | image     = NGC 2204 DSS.jpg
 | caption   = NGC 2204, Digitized Sky Survey
 | constellation = [[Canis Major]]
 | epoch     = J2000.0
 | ra        = {{RA|06|15|31.7}}<ref name=Tarricq_et_al_2021/>
 | dec       = {{DEC|−18|40|12}}<ref name=Tarricq_et_al_2021/>
 | dist_ly   = {{convert|4.1|±|0.4|kpc|kly|order=flip|abbr=on|lk=on}}<ref name=Jacobson_et_al_2011/>
 | dist_pc   = 
 | appmag_v  = 8.6<ref name=O'Meara_2007/>
 | size_v    = {{val|10.0|ul=arcminute}}<ref name=O'Meara_2007/>
 | mass_msol = 
 | radius_ly = 16.25ly
 | age       = {{val|2.0|0.3|ul=Gyr}}<ref name=Jacobson_et_al_2011/>
 | notes     = 
 | names     = [[Collinder catalogue|Collinder]] 88, [[Melotte catalogue|Melotte]] 44<ref name=SIMBAD/>
}}

'''NGC 2204''' is an [[open cluster]] of stars in the [[Canis Major]] [[constellation]]. It was discovered by the German-English astronomer [[William Herschel]] on 6 February 1785.<ref name=SEDS /> The cluster has an integrated visual magnitude of 8.6 and spans a diameter of {{val|10.0|ul=arcminute}}. Resolving the individual member stars is a challenge with a 10 to 12-inch amateur telescope.<ref name=O'Meara_2007/> It is located at a distance of approximately 13,400&nbsp;[[light years]] from the [[Sun]].<ref name=Jacobson_et_al_2011/> The cluster shows a mean [[radial velocity]] of {{val|+91.38|0.30|u=km/s}} relative to the Sun,<ref name=Mermilliod_Mayor_2007/> and is orbiting the inner galactic disk region about 1&nbsp;kpc below the [[galactic plane]].<ref name=Jacobson_et_al_2011/>

This is a rich but diffuse cluster with a [[Trumpler class]] of III 3m,<ref name=Hawarden_1976/><ref name=Dawson_1981/> spanning a physical diameter of about {{cvt|17|pc|ly|order=flip}}.<ref name=Rozyczka_2007/> It is an older cluster with an estimated age of {{val|2.0|0.3|u=billion years}}.<ref name=Salaris_et_al_2004/> The [[metallicity]] is correspondingly poor,<ref name=Siegel_et_al_2019/><ref name=Dawson_1981/> showing an abundance of iron about 59% of that in the Sun.<ref name=Jacobson_et_al_2011/> There is a prominent [[Red clump|giant branch clump]] on the [[HR diagram]].<ref name=Hawarden_1976/> The cluster has a significant population of [[blue straggler]]s,<ref name=Frogel_Twarog_1983/><ref name=Siegel_et_al_2019/> an indicator of past stellar mergers. It has a pair of candidate [[chemically peculiar star]]s,<ref name=Dawson_1981/> and five [[variable star]]s have been discovered, including four [[eclipsing variable]]s.<ref name=Rozyczka_2007/>

==References==
<references>
<ref name=SIMBAD>{{cite simbad
 | title=NGC 2204 | access-date=2024-03-09 }}</ref>

<ref name=Tarricq_et_al_2021>{{cite journal
 | title=3D kinematics and age distribution of the open cluster population
 | display-authors=1 | last1=Tarricq | first1=Y.
 | last2=Soubiran | first2=C. | last3=Casamiquela | first3=L.
 | last4=Cantat-Gaudin | first4=T. | last5=Chemin | first5=L.
 | last6=Anders | first6=F. | last7=Antoja | first7=T.
 | last8=Romero-Gómez | first8=M. | last9=Figueras | first9=F.
 | last10=Jordi | first10=C. | last11=Bragaglia | first11=A.
 | last12=Balaguer-Núñez | first12=L. | last13=Carrera | first13=R.
 | last14=Castro-Ginard | first14=A. | last15=Moitinho | first15=A.
 | last16=Ramos | first16=P. | last17=Bossini | first17=D.
 | journal=Astronomy & Astrophysics
 | volume=647 | at=id. A19 | date=March 2021
 | doi=10.1051/0004-6361/202039388 | arxiv=2012.04017
 | bibcode=2021A&A...647A..19T }}</ref>

<ref name=Jacobson_et_al_2011>{{cite journal
 | title=A Chemical Abundance Study of Red Giants in Open Clusters NGC 2204 and NGC 2243
 | display-authors=1 | last1=Jacobson | first1=Heather R.
 | last2=Friel | first2=Eileen D. | last3=Pilachowski | first3=Catherine A.
 | journal=The Astronomical Journal
 | volume=141 | issue=2 | id=58 | pages=16 | date=February 2011
 | doi=10.1088/0004-6256/141/2/58 | bibcode=2011AJ....141...58J | s2cid=120444023 | doi-access=free }}</ref>

<ref name=SEDS>{{cite web
 | last1=Frommert | first1=Hartmut | last2=Kronberg | first2=Christine
 | title=NGC 2204 | website=[[SEDS]] | access-date=9 July 2015
 | url=http://messier.seds.org/xtra/ngc/n2204.html }}</ref>

<ref name=O'Meara_2007>{{cite book
 | title=Herschel 400 Observing Guide
 | first=Stephen James | last=O'Meara | year=2007
 | page=48 | isbn=9780521858939
 | publisher=Cambridge University Press
 | url=https://books.google.com/books?id=Nyh9fAC_tpIC&pg=PA48 }}</ref>

<ref name=Salaris_et_al_2004>{{cite journal
 | title=The age of the oldest Open Clusters
 | display-authors=1 | last1=Salaris | first1=M.
 | last2=Weiss | first2=A. | last3=Percival | first3=S. M.
 | journal=Astronomy and Astrophysics
 | volume=414 | pages=163–174 | date=January 2004
 | issue=2 | doi=10.1051/0004-6361:20031578 | arxiv=astro-ph/0310363
 | bibcode=2011AJ....141...58J }}</ref>

<ref name=Mermilliod_Mayor_2007>{{cite journal
 | title=Red giants in open clusters. XII. Six old open clusters NGC 2112, 2204, 2243, 2420, 2506, 2682
 | last1=Mermilliod | first1=J. -C. | last2=Mayor | first2=M.
 | journal=Astronomy and Astrophysics
 | volume=470 | issue=3 | pages=919–926 | date=August 2007
 | doi=10.1051/0004-6361:20077198
 | bibcode=2007A&A...470..919M }}</ref>

<ref name=Siegel_et_al_2019>{{cite journal
 | title=The Swift UVOT Stars Survey. III. Photometry and Color-Magnitude Diagrams of 103 Galactic Open Clusters
 | last1=Siegel | first1=Michael H. | last2=LaPorte | first2=Samuel J.
 | last3=Porterfield | first3=Blair L. | last4=Hagen | first4=Lea M. Z.
 | last5=Gronwall | first5=Caryl A. | display-authors=1
 | journal=The Astronomical Journal
 | volume=158 | issue=1 | at=id. 35 | date=July 2019
 | doi=10.3847/1538-3881/ab21e1 | doi-access=free | arxiv=1905.04359
 | bibcode=2019AJ....158...35S }}</ref>

<ref name=Frogel_Twarog_1983>{{cite journal
 | title=Faint stellar photometry in clusters. I. NGC 2204 and E3
 | last1=Frogel | first1=J. A. | last2=Twarog | first2=B. A.
 | journal=Astrophysical Journal
 | volume=274 | pages=270–285 | date=November 1983
 | doi=10.1086/161445 | bibcode=1983ApJ...274..270F }}</ref>

<ref name=Hawarden_1976>{{cite journal
 | title=NGC 2204: an old open cluster in the halo
 | last=Hawarden | first=T. G.
 | journal=Monthly Notices of the Royal Astronomical Society
 | volume=174 | pages=225–239| date=January 1976
 | doi=10.1093/mnras/174.1.225 | doi-access=free | bibcode=1976MNRAS.174..225H }}</ref>

<ref name=Dawson_1981>{{cite journal
 | title=The open cluster NGC 2204
 | last=Dawson | first=D. W.
 | journal=Astronomical Journal
 | volume=86 | pages=237–241 | date=February 1981
 | doi=10.1086/112879 | bibcode=1981AJ.....86..237D }}</ref>

<ref name=Rozyczka_2007>{{cite journal
 | title=Variable Stars in the Field of the Open Cluster NGC2204
 | last1=Rozyczka | first1=M. | last2=Kaluzny | first2=J.
 | last3=Krzeminski | first3=W. | last4=Mazur | first4=B.
 | display-authors=1 | journal=Acta Astronomica
 | volume=57 | pages=323–329 | date=December 2007
 | arxiv=0803.1045
 | bibcode=2007AcA....57..323R }}</ref>
</references>

==External links==
* {{Sky-Map.org}}

{{Astronomical catalogs|Collinder=88|NGC=2204}}
{{NGC objects:2000-2499}}
{{Canis Major}}
{{Sky|06|15|33|-|18|39|54|1}}

{{DEFAULTSORT:NGC 2204}}
[[Category:Canis Major]]
[[Category:Open clusters]]
[[Category:NGC objects|2204]]
[[Category:Discoveries by William Herschel]]