Supernovae are usually a one-time event—once a star explodes, that’s it. But some white dwarfs have found a way to die twice. This happens in rare cases where a white dwarf partially explodes but doesn’t fully destroy itself. Instead, it lingers for a while, rebuilding mass by stealing gas from a companion star. Then, when it crosses a critical threshold again, boom—a second supernova. These “double detonation” supernovae were once thought impossible, but astronomers have now spotted them happening in real-time.
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