Researchers using the MMT’s Blue Channel Spectrograph have discovered a pair of white dwarfs circling one another at high speed, taking only 20 minutes to complete one orbit. Only eight other similar pairs are currently known. The new discovery is a fast one, with the orbital period the second-quickest of those already found. The two white dwarfs are about one-third and one-tenth the mass of the Sun and are expected to merge completely in less than 9 million years, slowly losing their angular momentum through gravitational wave radiation. The less massive white dwarf is “invisible,” remaining undetected by the observations with its presence inferred only from the orbital motion of the more massive white dwarf. The gravitational waves from this object may be of interest to upcoming space missions like eLISA. More details can be found here.