Open cluster in the constellation Canis Major
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. The cluster has an integrated visual magnitude of 8.6 and spans a diameter of . Resolving the individual member stars is a challenge with a 10 to 12-inch amateur telescope. It is located at a distance of approximately 13,400 light years from the Sun. The cluster shows a mean radial velocity of relative to the Sun, and is orbiting the inner galactic disk region about 1 kpc below the galactic plane.
This is a rich but diffuse cluster with a Trumpler class of III 3m, spanning a physical diameter of about . It is an older cluster with an estimated age of . The metallicity is correspondingly poor, showing an abundance of iron about 59% of that in the Sun. There is a prominent giant branch clump on the HR diagram. The cluster has a significant population of blue stragglers, an indicator of past stellar mergers. It has a pair of candidate chemically peculiar stars, and five variable stars have been discovered, including four eclipsing variables.
References.
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External links.
 ;indicator name="01-sky-coordinates" ; ;templatestyles src="Template:Sky/styles.css" / ;Coordinates: &amp;de=-18.665&amp;zoom=&amp;show_grid=1&amp;show_constellation_lines=1&amp;show_constellation_boundaries=1&amp;show_const_names=1&amp;show_galaxies=1&amp;img_source=IMG_all 06h 15m 33s, −18° 39′ 54″ ;/indicator ;