Meteor spectrum
A meteor spectrum is the light of a meteor split into colours, revealing which elements are glowing.
A meteor spectrum is made by passing the light of a meteor through a prism or diffraction grating, which spreads it into its component colours. Each chemical element glows at particular wavelengths, so bright lines in the spectrum reveal which elements are present in the meteoroid and in the heated air around it.
Common lines come from sodium, which glows yellow-orange; magnesium, blue-green; iron, which gives many lines; and calcium. Nitrogen and oxygen from the air also glow, giving red light in the lower parts of the trail. The proportions of sodium, magnesium and iron can indicate whether a meteoroid is chondrite-like, iron-rich or depleted in sodium.
Some camera networks now record spectra routinely. They show, for example, that Geminid meteoroids are often depleted in sodium, probably because their parent Phaethon is heated close to the Sun. Spectra help connect meteors with known meteorite types without recovering any material.
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