Red Giant

A red giant is a star in a late stage of its life, characterized by enormous size, relatively low surface temperature, and a distinctive reddish hue. When a star like our Sun exhausts the hydrogen fuel in its core, it begins fusing hydrogen in a shell around the core, causing the outer layers to expand dramatically—sometimes swallowing inner planets. A red giant can be 100 times larger than the Sun while being only slightly more massive.

These stellar giants are laboratories of cosmic alchemy: their cores reach temperatures hot enough to fuse helium into carbon and oxygen. Red giants populate the upper-right region of the Hertzsprung-Russell diagram, a fundamental tool in stellar classification. Eventually, after shedding their outer layers into space, red giants leave behind white dwarfs—the dense, Earth-sized remnants of once-mighty stars.

Observing red giants reveals how matter transforms across cosmic timescales and helps astronomers understand stellar evolution, the fate of stars, and the origins of heavy elements that make planets and life possible.

Related

Star, White Dwarf, Hertzsprung-Russell diagram, Stellar evolution, Helium fusion, Planetary systems