Ultraviolet Astronomy

UV telescopes reveal a wealth of information about hot and energetic processes in astronomical objects. This is because the hotter an object is, the more energy it radiates at short wavelengths. UV radiation has shorter wavelengths than visual light, so hot objects are brighter in the UV than in the visual. For example, a hot star like Rigel (the blue-white star that forms Orion's left foot) emits much more UV radiation than the Sun.

UV telescopes have greatly enhanced our understanding of the stars. It is well-known that the temperature rises in the outer atmospheres of stars like the Sun, but the causes of this temperature rise are poorly understood. Because the atmospheres get very hot, they emit much of their radiation in the UV, and until the launch of IUE in 1978, the nature of these hot atmospheres was largely unknown. UV telescopes have also been used to study winds from hot stars, stars that are still in the process of forming, and hot, dead stars that orbit other stars, drawing matter off them and heating it until it emits large amounts of UV and x–ray radiation.

Another place where hot, high-energy conditions prevail is at the center of galaxies. The so-called active galaxies have intense high-energy sources at their centers. These galaxies often have huge jets of hot, high-energy material streaming out of them. A hypothesized source of the intense energy generation is an enormous black hole at the galactic center. IUE and other UV telescopes have been used to study galactic centers in an effort to understand the processes occurring in the crowded, violent environments thought to prevail there.