OBAFGKM

OBAFGKM is a classification system for stars based on their spectral features and temperature. The letters run from hottest to coolest: O (blue, very hot), B (blue-white), A (white), F (yellow-white), G (yellow, like our Sun), K (orange), and M (red, cooler). This sequence helps astronomers identify a star's properties, such as temperature and composition, by analyzing its light spectrum. The classification reflects both the star's temperature and certain atmospheric characteristics, providing a standardized way to categorize the vast diversity of stars in the universe.