Collinder 60

Collinder 60 is a rich open star cluster in the constellation Taurus, also known as Cr 60 and NGC 1817. It is about 5,900 to 6,400 light-years away (roughly 1.97 kiloparsecs). It spans about 20 arcminutes and holds around 170 to 280 member stars (stars of magnitude 11 to 14). It stands out as an old cluster, about 0.8 to 1.2 billion years old, similar to the Hyades, though with a lower heavy-element abundance. It has an unusually high proportion of Delta Scuti variable stars (16 among 26 variables found), probably because its main-sequence turn-off lies in the instability strip. It lies about 26 arcminutes from NGC 1807 (Collinder 59), which a proper-motion study found not to be a separate cluster: the two may be parts of a single extended cluster, or NGC 1807 is only an asterism with a few stars that match NGC 1817. At magnitude 7.7 it is easily seen in binoculars, and William Herschel discovered it on 19 February 1784.