We have discovered that the detached double degenerate binary WD 0957-666 has an orbital period of 1.46 hours , rather than the 1.15 day orbital period reported earlier .
This is the shortest period example of such a system yet discovered .
We obtain a unique period , which fits both our and earlier data .
At this period the emission of gravitational radiation will cause the binary to merge within approximately 2.0 x 10 ^ { 8 } years .
This system represents a population of short orbital period binaries which will merge within a Hubble time , and so could account for type Ia supernovae , although due to the low mass of both stars ( 0.3 to 0.4 M _ { \odot } ) , it is unlikely to become a supernova itself .
We have detected the companion star and have measured a mass ratio of q = 1.15 \pm 0.10 .
This is the third double degenerate for which q has been measured and all three have q \simeq 1 , which is in conflict with the predicted mass ratio distribution which peaks at 0.7 .
This system is viewed close to edge on , and we estimate that the probability of this system undergoing eclipses is 15 % .