THE AGE OF THE GLOBULAR-CLUSTER M68

Relying on the accurate color-magnitude diagram (CMD) presented by Wal ker in 1994, we use the fitting of moderately hot horizontal-branch mo dels to the observed CMD to derive suitable information regarding both cluster reddening and distance modulus and to discuss theoretical pre dictions constraining the absolute age of the metal-poor Galactic glob ular cluster M68. As a first step, we show that such a procedure, when based on an ''old'' theoretical evolutionary scenario, agrees with si milar evaluations already given in the literature, predicting an age o f the order of 13-14 Gyr for the cluster. We show that adopting update d theoretical models, which include all recent improvements in the inp ut physics and in which element diffusion is taken into account, decre ases current estimates of the age of M68 to 10 Gyr. Possible sources o f errors in our estimate are briefly discussed in light of recent resu lts from the HIPPARCOS satellite. The relevance of comparing M68 with other metal-poor Galactic globular clusters is finally discussed, sugg esting that the age of M68 could perhaps represent the common age of a ll these clusters and weakening considerably current claims for a conf lict with cosmological ages.