A nova is a sudden, short-lived explosion from a compact star not much larger than Earth. The outburst comes from a collapsed star known as a white dwarf, which circles so close to a normal star that a stream of gas flows between them. This gas piles up into a layer on the white dwarf's surface until it reaches a flash point and detonates in a runaway thermonuclear explosion. Astronomers estimate that between 20 and 50 novae occur each year in our galaxy, but despite their power most go undis...
