NGC 2506 -- Open Cluster in Monoceros
Old & Still Looking Good
Although Messier missed this impressive open cluster, Sir Patrick Moore (Caldwell 54) and
the Astronomical League’s Herschel 400 list, did not. Immersed in a star-rich section of the
Milky Way, this rich, condense, collection-of-stars jumps out at the eyepiece.
NGC 2506 is old for an open cluster. Dates vary from 3.4 billion to 2.0 billion years old. Most
open clusters cease to exist by this age, scattering their stars into open space. No doubt, the
reasonably tight sphere of its 800+ stars has allowed for enough continued gravitational
attraction to keep it together for its billions of years of existence.
None of the cluster’s stars are bright. Many of the Milky Way stars surrounding the cluster are
as bright, or brighter, than the cluster’s brightest members. But when searching for this cluster,
the combined light of its numerous hidden unresolved stars provides a cotton-like background
that is impossible to miss.