The hotter a star, the bluer it appears. This is because the hotter a star is, the more energy it emits in the form of blue and ultraviolet light. In contrast, cooler stars appear redder because they emit more energy in the form of red and infrared light.
The surface temperature of a star is determined by several factors, including the star's mass and age. More massive stars are hotter than less massive stars, and younger stars are hotter than older stars.
The color of a star can also be affected by the presence of elements other than hydrogen and helium in the star's atmosphere. For example, the presence of iron can make a star appear redder, while the presence of hydrogen can make a star appear bluer.
The color of a star can be used to determine the star's temperature and other characteristics, such as its mass and age.
