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Animation of a red giant star with a hot planet in a close orbit. Red giants are a late stage in the life of a Sun-like star. They typically burn hydrogen in a shell around an inert core of helium. This inflates the outer layers of the star, causing them to expand and cool. This makes them much larger and redder than while they were fusing hydrogen in their cores. The expansion of the star's outer layers would engulf close planets and scorch ones even at Earth-like distances. The Sun will swell into a red giant and probably engulf the Earth in some five billion years