Study of astronomical objects and phenomena by observing the ultraviolet radiation (UV radiation) they emit.
It has yielded much information about chemical abundances and processes in interstellar matter, the Sun, and other stellar objects, such as hot young stars and white dwarf star s. Ultraviolet astronomy became feasible once rockets could carry instruments above Earth's atmosphere, which absorbs most electromagnetic radiation of UV wavelengths. Since the early 1960s, a number of unmanned space observatories carrying UV telescopes, including the Hubble Space Telescope , have collected UV data on objects such as comet s, quasar s, nebula e, and distant star clusters. The Extreme Ultraviolet Explorer, launched in 1992, was the first orbiting observatory to map the sky in the shortest UV wavelengths, at the boundary with the X-ray region of the electromagnetic spectrum .