Blackbody radiation and continuous, emission, and absorption spectra

A hot, dense object such as a star glows with a continuous range of colors called blackbody radiation. The hotter it is, the shorter the wavelength at which its glow peaks and the more energy each square meter gives off, so cool stars look red, the Sun looks yellow-white, and very hot stars look blue-white. Three kinds of spectra help classify celestial objects. A hot, dense source gives a continuous spectrum, a smooth rainbow. A hot, thin gas, like a glowing nebula, gives an emission spectrum of bright lines at wavelengths set by its elements. Cooler gas in front of a hotter continuous source gives an absorption spectrum, a rainbow crossed by dark lines at those same wavelengths; this is what most stars show, because their cooler outer layers absorb light from the hotter layers below. Astronomers use these patterns to sort stars into spectral classes, O, B, A, F, G, K, and M, from hottest to coolest.

This explanation is AI-generated and can occasionally be wrong. 🚩 Report