... M3: Inconstant Star Cluster . ... In reality, though, cluster stars swarm the center and frequently fluctuate in brightness. ... Moon Lightning . ... But amateur astronomer Marc-Andre Besel was impressed by the brilliant lighting displays that joined the first quarter Moon and stars of the constellation Scorpius in western skies. ... The center of the open cluster, visible on the upper right, formed only about two million years ago and is dominated in brightness by a host of bright young blue stars....