In roughly 5 billion years, the sun will run out of energy and drastically alter the solar system. Oceans will be baked dry. Entire planets will be consumed. And long-icy worlds will finally enjoy their day in the sun.Our star is powered by nuclear fusion, and it turns hydrogen into helium in a process that converts mass into energy. Once the fuel supply is gone, the sun will start growing dramatically. Its outer layers will expand until they engulf much of the solar system, as it becomes what astronomers call a red giant.The life cycle of the sun takes it from the life-giving star we know today into a swelling red giant and, eventually, a planetary nebula surrounding a tiny white dwarf. (Credit: ESO/S. Steinhöfel)And what will happen to the planets once the sun enters the red giant phase? The solar system’s denouement is still a subject of debate among scientists. Exactly how far the dying sun will expand, and how conditions will change, aren’t yet clear. But a few things…



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