Glossary - Astronomy Magazine

Comet C/2011 L4 (PANSTARRS)

Comet C/2012 S1 (ISON)

Glossary

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ultraviolet light radiation with higher energy than visible light, but without as much energy as x rays
ultraviolet radiation radiation with higher energy than visible light, but without as much energy as x rays
umbra 1. the dark, central region of a shadow from which none of the light source can be seen 2. the dark center of a sunspot
unidentified infrared bands (UIBs) mysterious objects in space that give off as yet unidentified infrared emission patterns

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