Light from a star can be separated into its component colors to form a spectrum. The spectrum reveals details in the brightness of different colors of starlight that are not visible to the naked eye. Detectors in the telescope can measure the precise brightness of individual wavelengths. Those data can be plotted on a graph of brightness vs. wavelength. Astronomers can then use the graph to make inferences about the temperature, composition, motion, and other characteristics of the star. Our understanding of the composition, temperature, and motion of Altair is based on its spectrum.
Credits
Illustration
NASA, ESA, Leah Hustak (STScI)
