American astronomer

Annie Jump Cannon developed a stellar classification system that is considered by many astronomers to be the foundation of stellar spectroscopy. The science of stellar spectroscopy analyzes the photographic spectrum of a star. The spectrum, a series of colors that can range from violet to red depending on the star's temperature, is produced by using a telescope to collect a star's light and to pass it through a spectroscope. The same effect occurs when sunlight passes through raindrops to produce a rainbow. The spectroscope also produces a series of narrow dark lines within the spectrum known as spectral lines. These lines give further clues to a star's temperature as well as composition, motion, and other information. Because the position of the spectral lines on the spectrum may vary greatly from one star to another, scientists sometimes refer to this spectrographic...