An Etymological Dictionary of Astronomy and Astrophysics
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A → variable star that shows a sudden and dramatic change in brightness, including → flare stars, → novae, and some types of → symbiotic stars. They are believed to be very → close binary systems consisting of an → accreting → white dwarf  → primary and an evolved → late-type secondary star that has filled its → Roche lobe. For systems with an → accretion disk, it is believed that a thermal instability is the cause of repetitive outbursts observed in cataclysmic variables called → dwarf novae.

→ cataclysmic; → variable.