Ultraviolet astronomy provide essential information about the evolution of galaxies. The ultraviolet universe looks quite different from the familiar stars and galaxies seen in visible light. Most stars are actually relatively cool objects emitting much of their electromagnetic radiation in the visible or near-infrared part of the spectrum. Ultraviolet radiation is the signature of hotter objects, typically in the early and late stages of their evolution. In the Earth's sky seen in ultraviolet light, most stars would fade in prominence. Some very young massive stars and some very old stars and galaxies, growing hotter and producing higher-energy radiation near their birth or
Ultraviolet communication in butterflies to reflect ultraviolet light. In effect, females are removing the ultraviolet signal that initiates male sexual behavior, resulting in the abrupt halt of male sexual behavior. Female White Cabbage Butterflies take advantage of the personal butterfly ultraviolet communication system to also reject males by removing an ultraviolet reflectance signal. Some butterfly species use ultraviolet light as a method of signaling their sex. For example, in the species "Eurema lisa", males possess the structural requirements necessary to reflect ultraviolet light discussed previously, but females lack the ultraviolet light reflecting ridges. In both sexes of this species, a flutter response, or the