The Hertzsprung-Russell Diagram

The Hertzsprung-Russell Diagram, often abbreviated as H-R diagram, is a fundamental tool in astrophysics used to classify stars based on their luminosity, temperature, spectral type, and evolutionary stage. Named after astronomers Ejnar Hertzsprung and Henry Norris Russell, this diagram plots stars' luminosity against their temperature or spectral type, revealing patterns and relationships crucial for understanding stellar evolution and the life cycle of stars. Its simplicity belies its significance, serving as a cornerstone in modern astronomy for classifying and interpreting the properties of stars across various stages of their existence.