  Optical spectroscopy is used to confirm membership for 8 low-mass candidates
in the young Beta Pic moving group (BPMG) via their radial velocities,
chromospheric activity and kinematic parallaxes. We searched for the presence
of the Li I 6708A resonance feature and combined the results with literature
measurements of other BPMG members to find the age-dependent lithium depletion
boundary (LDB) -- the luminosity at which Li remains unburned in a coeval
group. The LDB age of the BPMG is 21 +/- 4 Myr and insensitive to the choice of
low-mass evolutionary models. This age is more precise, likely to be more
accurate, and much older than that commonly assumed for the BPMG. As a result,
substellar and planetary companions of BPMG members will be more massive than
previously thought.
