AM CVn

An AM CVn star (where CVn stands for the stellar constellation Canes Venatici in which the prototype of this class was discovered) is a type of cataclysmic variable star, in which a White Dwarf accretes helium-rich matter from another White Dwarf. These binary stars have extremely short orbital periods (shorter than about one hour), and are predicted to be strong sources of gravitational wave radiation: strong enough to be detected with the Laser Interferometer Space Antenna.