Prism Animation

Spectroscopy splits light into its components to reveal the "fingerprints" of various chemicals.

Extensive observations were made with Hubble's Near Infrared Camera and Multi-Object Spectrometer (NICMOS) as planet HD 189733b passed in front of its parent star in what astronomers call a transit. As the light from the star passed briefly through the atmosphere along the edge of the planet, the gases in the atmosphere imprinted their unique signatures on the starlight from the star HD 189733.