Berkeley 17: The Oldest Open Cluster?

Faint magnitude BV I CCD photometry of the central region of the old open cluster Berkeley 17 (Be 17) has been undertaken to investigate the claim that it is the oldest open cluster yet discovered (Phelps, Janes, & Montgomery). This study reveals Be 17 to have a metallicity [0.30 [Fe/H] 0.00 ; a reddening 0.52 E(B[V ) 0.68 or 0.61 E(V [I) 0.71 ; a distance modulus, (m [ M) 0 \ 12.15 corresponding to a distance of 2.7 ^0.1 kpc ; a diameter of D10 pc ; a minimum mass of 400 ^0.10, and an age of 1013 Gyr. With an adopted age of Gyr, these results suggest that Be 17 is M _ ; 1 2 ~2 `1 indeed the oldest open cluster yet discovered. The inferred old age for Be 17 indicates that the cluster is an important one for studies of the di erences between open and globular clusters, the transition from the halo/thick disk to the thin disk of the Galaxy, and even for establishing the minimum age of the universe.