BERKELEY-17 - THE OLDEST OPEN CLUSTER

Faint magnitude BVI CCD photometry of the central region of the old op en 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 less than or equal to [Fe/H] less than or equal to 0.00; a reddening 0 .52 less than or equal to E(B-V) less than or equal to 0.68 or 0.61 le ss than or equal to E(V-I) less than or equal to 0.71; a distance modu lus, (m - M)(0) = 12.15 +/- 0.10, corresponding to a distance of 2.7 /- 0.1 kpc; a diameter of similar to 10 pc; a minimum mass of 400 M.; and an age of 10-13 Gyr. With an adopted age of 12(-2)(+1) Gyr, these results suggest that Be 17 is indeed the oldest open cluster yet disco vered. The inferred old age for Be 17 indicates that the cluster is an important one for studies of the differences between open and globula r clusters, the transition from the halo/thick disk to the thin disk o f the Galaxy, and even for establishing the minimum age of the univers e.