The Hertzsprung–Russell Diagram

The Hertzsprung-Russell diagram (H-R diagram) is a crucial tool in astronomy that plots stars according to their brightness and temperature. On the horizontal axis, stars are arranged by temperature, which decreases from left to right. The vertical axis shows their brightness, or luminosity, increasing upwards. This diagram reveals patterns in stellar evolution, highlighting groups like main-sequence stars (where most stars, including our Sun, are found) and giants or supergiants. By understanding a star's position on the H-R diagram, astronomers can infer its age, size, and stage in its lifecycle.