International Ultraviolet Explorer was considered the most successful astronomical satellite ever. The human eye can perceive light with wavelengths between roughly 350 (violet) and 700 (red) nanometres. Ultraviolet light has wavelengths between roughly 10 nm and 350 nm. UV light can be harmful to human beings, and is strongly absorbed by the ozone layer. This makes it impossible to observe UV emission from astronomical objects from the ground. Many types of object emit copious quantities of UV radiation, though: the hottest and most massive stars in the universe can have surface temperatures high enough that the vast majority of their light is emitted
The empire on which the sun never sets expression, the sun never sets in the Spanish dominions, but ever shines upon one part or other of them : which, to say truly, is a beam of glory [...]". Thomas Urquhart wrote of "that great Don Philippe, Tetrarch of the world, upon whose subjects the sun never sets." In the German dramatist Friedrich Schiller's 1787 play, "Don Carlos", Don Carlos's father, Philip II, says, "" ("I am called / The richest monarch in the Christian world; / The sun in my dominion never sets."). Joseph Fouché recalled Napoleon saying before the Peninsular War, "Reflect that the sun never sets