Classes of Stars

Classes of Stars

Stars are classed according to their spectra. The photosphere of a star emits photons at all wavelengths, but the emission at some wavelengths is stronger than at others depending on the composition of the hot glowing gasses in the star.
We can see examples of that here on Earth. The tubes of excited neon gas in a neon sign emit pure red light, while the hot sodium gas in a sodium lamp emits yellow light. In a star, the photosphere is composed of a variety of chemical elements, so the spectrograph of a star (see image above) can be quite complex. MORE! [TB] {EA}