Cataclysmic binary. Computer artwork of a cataclysmic binary star system. Gas is being sucked from a red dwarf star (right) toward a dense, strongly-magnetic white dwarf (left). The gas forms an accretion disc around the smaller star. Extreme rotation speeds within the disc generate temperatures high enough for the emission of X-rays. Periodically the gas may explode on the surface of the white dwarf. These novae may greatly increase the brightness of the binary system. Here, the white dwarf has illuminated the red dwarf, creating a shadow of the accretion disc on its surface.