This cluster has an angular core radius of 18″ and a physical radius of approximately 47 ly.[3] It has a combined 4,200[3] times the mass of the Sun and is around 250 million years old.[4] The metallicity of the cluster – what astronomers term the abundance of elements with higher atomic number than helium – is at around −0.62, or only 24% of that in the Sun. The turn-off mass for the cluster, when a star of that mass begins to evolve off the main sequence into a giant, is about 4.0 to 4.5 M☉.[7]