The large sample of main sequence stars with Hipparcos parallaxes and estimates of the radial velocity has been used to study the relations among kinematics , age and heavy element content for the solar neighbourhood .
The samples with V > -30 km s ^ { -1 } , although including stars as old as 10 ^ { 10 } yr , have a very young component ( age \buildrel > \over { \sim } 10 ^ { 7 } yr ) , and have a metallicity close to the solar one .
Most of the stars with space velocity component V < -40 km s ^ { -1 } have a minimum age of about 2 10 ^ { 9 } yr. Stars with V \buildrel < \over { \sim } -80 km s ^ { -1 } share a common age \buildrel > \over { \sim } 10 ^ { 10 } yr .
The distribution in [ Fe/H ] of these latter objects suggests a decrease in metal content with increasing |V| till [ Fe/H ] < -2 .
For V < -180 km s ^ { -1 } only the metal poor component ( [ Fe/H ] < -0.7 ) is found .
The common age for large space velocity suggests that no substantial age spread exists in the inner halo , at least in the local sample .