Comet C/2001 Q4, also known as NEAT, emits a blue-and-purple glow as it moves through the cosmos in May 2004. Its coma, or head, and a portion of its tail are visible in this shot, as are myriad ...

Emission spectra of comet P/Halley in the 275-710 nm wavelength range were obtained using a spectrometer mounted on the Vega 2 spacecraft, which encountered the comet on Mar. 9, 1986. The spectra, ...