Color-magnitude diagram of stars that are members of the Blanco 1 cluster

Color-magnitude diagram of stars that are members of the Blanco 1 cluster, along with some nearby non-members. The lithium-rich stars (red squares) show lithium absorption in their spectra, unlike the lithium-poor objects (blue circles). The boundary between the two groups depends on the age of the cluster, which the inset shows to be around 130 million years.