Spectroscopy

The Spectrum

Visible light, the light our eyes can see, consists of an array of colors called a spectrum. These colors can be seen when sunlight passes through mist or a pane of glass and forms a rainbow. Within the light lie hidden patterns, which an instrument called a spectroscope can detect. These patterns reveal much about the object emitting the light, including what it is made of and how it is moving.

Shining a beam of light through a prism spreads the light out into its array of colors. This happens because the light bends as it passes through the glass of the prism, and some parts of the light are bent more than others.

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Chemical Composition

Something remarkable happens when starlight passes through a thin slit and is aligned by a lens and spread out by a prism: parallel lines appear on the resulting spectrum. The lines indicate chemical elements present in the star emitting the light. Every element produces a pattern of lines as unique as a fingerprint. By sorting out the overlapping patterns in a spectrum, it is possible to figure out what the star is made of. Spectra, therefore, provide a way to study the composition and physical state of distant celestial objects.