We present spectra of the pulsating sdB star KPD 1930+2752 which confirm that this star is a binary .
The radial velocities measured from the H \alpha and HeI 6678Å spectral lines vary sinusoidally with the same period ( 2 ^ { h } 17 ^ { m } ) as the ellipsoidal variability seen by Billères et al .
( 2000 ) .
The amplitude of the orbital motion ( 349.3 \pm 2.7 km s ^ { -1 } ) combined with the canonical mass for sdB stars ( 0.5 M _ { \odot } ) implies a total mass for the binary of 1.47 \pm 0.01 M _ { \odot } .
The unseen companion star is almost certainly a white dwarf star .
The binary will merge within \sim 200 million years due to gravitational wave radiation .
The accretion of helium and other elements heavier than hydrogen onto the white dwarf which then exceeds the Chandrasekhar mass ( 1.4 M _ { \odot } ) is a viable model for the cause of Type Ia supernovae .
KPD 1930+2752 is the first star to be discovered which is a good candidate for the progenitor of a Type Ia supernova of this type which will merge on an astrophysically interesting timescale .