Positioned approximately 440 parsecs distant,[129] the cluster is estimated to be around 800 million years old, quite old for an open cluster.[130] Despite the presence of the Milky Way in Serpens Cauda, one globular cluster can be found: NGC 6535, although invisible to the naked eye, can be made out in small telescopes just north of Zeta Serpentis. Rather small and sparse for a globular cluster,[131] this cluster contains no known RR Lyrae variables, which is unusual for a globular cluster.[132]