HD (Henry Draper) numbers

Henry Draper (HD) numbers are a system used to classify and catalog stars based on their spectral characteristics, which reveal their temperatures, compositions, and other properties. Created in the 19th century by astronomer Henry Draper, this system assigns unique identifiers to stars, making it easier for astronomers to study and reference them. Each HD number corresponds to a specific star, enabling researchers to access detailed information about its characteristics, behavior, and position in the sky. The HD catalog serves as an important resource for both professional astronomers and enthusiasts alike.