NGC 2506 (also known asCaldwell 54) is a mildly-elongated[6]open cluster of stars in theequatorialconstellation ofMonoceros, located at a distance of 12.7 kly[2] from the Sun near the Galactic anti-center.[4] It was discovered byWilliam Herschel in 1791.[7] The cluster lies around10,000 ly from theGalactic Center and about1,600 ly above theGalactic plane.[4] It is of intermediate age,[2] estimated at around two billion years.[2] The cluster has an angular radius of12′ and a core radius of4.8′.[8]
At least 94 probable members have been identified within the field of NGC 2506 based upon theirradial velocities. Compared to the Sun, the cluster is moderatelymetal-poor with an iron abundance of [Fe/H] = –0.3 dex.[9] It shows indications of mass segregation, with the lower mass members being more likely to be in the outer parts of the cluster. This is the result of exchange of kinetic energy during encounters between the members.[10] Twelveblue straggler stars have been located in the cluster, with three of them showing short-period oscillation. FourteenGamma Doradus variables have been found, as well as twodetachedeclipsing binaries,[6] and threeDelta Scuti stars.[11]
^Kim, S. -L.; et al. (March 2001). "Search for Variable Stars in Two Old Open Clusters: NGC2506 and NGC2420".Acta Astronomica.51:49–63.Bibcode:2001AcA....51...49K.
Media related toNGC 2506 at Wikimedia Commons
