Analyze absorption and emission spectra to identify chemical elements.
When light passes through a prism, it spreads into a spectrum. Each element produces unique spectral lines: Emission spectra (bright lines) from excited gas, and Absorption spectra (dark lines in continuous) from gas absorbing specific wavelengths. Astronomers use these "fingerprints" to identify elements in stars, nebulae, and exoplanet atmospheres without visiting them.