NGC 2204

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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 Template:Val. 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 light years from the Sun.<ref name=Jacobson_et_al_2011/> The cluster shows a mean radial velocity of Template:Val relative to the Sun,<ref name=Mermilliod_Mayor_2007/> and is orbiting the inner galactic disk region about 1 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 Template:Cvt.<ref name=Rozyczka_2007/> It is an older cluster with an estimated age of Template:Val.<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 giant branch clump on the HR diagram.<ref name=Hawarden_1976/> The cluster has a significant population of blue stragglers,<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 stars,<ref name=Dawson_1981/> and five variable stars have been discovered, including four eclipsing variables.<ref name=Rozyczka_2007/>

External links

• Template:Sky-Map.org