Cataclysmic variable binary star system. Image 2 of 2. Artwork of the high state of this binary star system. A red dwarf star (upper left) is in mutual orbit with a white dwarf star (lower right) that has an accretion disc (red) forming around it. This disc forms as the gravity of the white dwarf star pulls material from the red dwarf star. In this high state (which could lead to a sudden explosive increase in brightness called a nova), the high flow of material brightens and swells the accretion disc and creates the shadow on the red dwarf star. See image R670/175 for the low state. A white dwarf is a collapsed star with an intense gravitational field.