Glossary term: Hertzsprung-Russell (HR) Diagram

Description: The Hertzsprung–Russell (or HR) diagram is a graph of two observational properties of stars: the total power emitted by stars (luminosity) and the temperature on the stellar surface (effective temperature). Plotted on logarithmic scale, the effective temperature is typically displayed inversely, i.e. increasing from right to left. The HR diagram is named after two scientists: Ejnar Hertzsprung and Henry Norris Russell who first made this graph to understand the properties of stars. The main-sequence stars lie on a diagonal band in this graph, giant stars lie above the main-sequence band to the right, and the white dwarfs lie below the band to the left. The HR diagram is used to understand the different phases stars pass through, as they evolve.

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