The Hertzsprung-Russell diagram and main-sequence stars

The Hertzsprung-Russell (H-R) diagram plots stars by their luminosity (true brightness) against their surface temperature, with hotter stars drawn on the left. About 90 percent of stars fall along a band called the main sequence, where they fuse hydrogen into helium in their cores and are made mostly of hydrogen and helium. Along the main sequence, mass is the key: more massive stars are hotter, larger, and far more luminous, and they burn through their fuel so much faster that they live only a few million years, while low-mass red dwarfs can last many billions of years. Red giants and supergiants appear in the upper right, cool but very luminous because they are enormous, and white dwarfs appear in the lower left, hot but dim because they are tiny. A star moves across the diagram as it ages: a Sun-like star leaves the main sequence to become a red giant and ends as a white dwarf. In a star cluster, whose stars all formed at about the same time, the point where stars are leaving the main sequence reveals the cluster's age.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report