From the outlook of a planet that resides next to a quiet, relatively predictable star, the circumstances that lead to dramatic stellar explosions elsewhere in the universe can sound somewhat improbable. Some such blasts, known as type Ia supernovae, occur when a small, dense star known as a white dwarf--roughly the diameter of Earth, but hundreds of thousands of times more massive--grows too large by siphoning material off a neighboring star, igniting a thermonuclear explosion. Other cataclysms, known as type II supernovae, occur when much heftier stars, some of them dozens of times as massive as the sun, implode under their own weight. [More]




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