How are rainbows and spectroscopy connected?
By splitting starlight into its constituent colours – a technique known as spectroscopy – astronomers can learn more about the objects they study.
When the light of a star or galaxy is spread out into what is called a spectrum – comparable to a rainbow – certain colours appear to be missing. The strength, width and position, or wavelength, of each absorption line provide astronomers with valuable information about the motion and chemical composition, among other things, of the object under study. Thus, spectroscopy is a powerful astronomical tool. In 1995, spectroscopic observations even revealed the existence of the first exoplanet orbiting a Sun-like star.
Astronomers can spread the light of objects in the sky into a mini-rainbow. Its spectrum is like the object’s fingerprint – it contains a lot of useful information.