WD 1704+481 is a visual binary in which both components are white dwarfs . We present spectra of the H \alpha line of both stars which show that one component ( WD 1704+481.2 = Sanduleak B = GR 577 ) is a close binary with two white dwarf components . Thus , WD 1704+481 is the first known triple degenerate star . From radial velocity measurements of the close binary we find an orbital period of 0.1448d , a mass ratio , q = \frac { M _ { bright } } { M _ { faint } } of q = 0.70 \pm 0.03 and a difference in the gravitational redshifts of 11.5 \pm 2.3 { km s } ^ { -1 } . The masses of the close pair of white dwarfs predicted by the mass ratio and gravitational redshift difference combined with theoretical cooling curves are 0.39 \pm 0.05 { M } _ { \odot } and 0.56 \pm 0.07 { M } _ { \odot } . WD 1704+481 is therefore also likely to be the first example of a double degenerate in which the less massive white dwarf is composed of helium and the other white dwarf is composed of carbon and oxygen .