The star V838 Monocerotis shocked astronomers in 2002 when it suddenly expanded and started pulsing with light. It wasn’t a typical explosion—it was more like a massive cosmic heartbeat, sending ripples of brightness through space. The cause? No one knows for sure. Some think it was a failed supernova, while others suggest it swallowed a nearby planet. Whatever happened, the light echoes it created gave us some of the most stunning space images ever captured.