|the study of radiation from celestial sources in the wavelength range 91.2 to 320 nanometres, 12 to 91.2 nanometres being the extreme ultraviolet range|
|a chattering or flighty, light-headed person.|
|a screen or mat covered with a dark material for shielding a camera lens from excess light or glare.|
The study of celestial objects by measurement of the ultraviolet radiation they emit. Celestial objects with strong emissions in the ultraviolet range are usually significantly hotter than those whose emissions are stronger in the visible range. Because the ozone layer absorbs most ultraviolet radiation before it reaches the Earth's surface, most ultraviolet observations are made from rocket-borne or space-based instruments.