Ultraviolet astronomy
Ultraviolet astronomy is devoted to the study of astronomical objects in the ultraviolet (UV) radiation. In Astronomy electromagnetic radiation having a wavelength between about 10 and 380 nanometers (nm) is designated as ultraviolet. This wavelength range is generally further divided into the near- UV ( NUV, 200-380 nm), the far- UV ( FUV, 100 to 200 nm) and extreme ultraviolet (EUV, 10 to 100 nm). Short Wavey, the X-ray astronomy connects to the UV region.
History
Because the UV radiation is absorbed to a large extent already in the stratosphere, mainly due to the oxygen or ozone, is an observation by earth stations - also from Bergen - not possible. Initially, measurements were carried out in the near UV range up to about 200 nm wavelength of research balloons, which could penetrate up to altitudes of about 45 km. Starting in 1962, an observation with the help of satellites was possible with the help of the eight Orbiting Solar Observatory satellites, which, however, served only to observe the Sun. From 1972 there was also the opportunity to observe other objects, among others, in the UV region with Copernicus and similar European satellites. However, the ultraviolet astronomy only gained significantly in importance, as was 1978 to 1996 the International Ultraviolet Explorer ( IUE ) for nearly two decades are available, as is the Hubble Space Telescope UV instruments on board and allowed a further improvement of the results. 2003 has been started to observe in the ultraviolet GALEX with another satellite. The researchers were thus access to light with wavelengths down to 105 nm, which is due to the special mirror coating of Copernicus. Ordinary coatings of the mirrors used in high performance telescopes are opaque below 160 nm. Therefore, one has chosen a coating of LiF in this satellite, which is, however, hygroscopic and therefore made difficulties before the start in the humid climate of Florida. A further advance in areas of shorter wavelengths down to 10 nm is only possible with a grazing incidence of light on the mirror of the telescope.
Importance
The UV region is among other things especially for the study of hot stars that shine intensely in the UV. Similarly, there are types of extragalactic objects with intense UV radiation. In addition to the objects themselves and the interstellar matter between the Earth and the observed object can be well studied, since in the UV region, there are numerous interstellar absorption lines. These radiation below 91.2 nm wavelength is absorbed very strong, because it is ionised at this energy, the hydrogen in the H- II areas. Transparent these areas again, for light with wavelengths of about 10 nm - an area that has yet to be explored. Unlike the other branches of modern astronomy, such as the X-ray, radio and infrared astronomy has not discovered with the UV astronomy primarily novel objects such as X-ray sources or cold protostars. Rather, it is operated by the methods of optical astronomy and primarily Spectroscopic Investigations of the physical composition or radial velocity will be especially hot carried out stars. The advantage over the optical astronomy lies in the large number of spectral lines in this wavelength range, even at the frequently occurring elements in the universe, such as the well-known Lyman series. With the help of ultraviolet astronomy was able to learn much more about gas flows around hot stars and in binary systems. But could also be recovered within our solar system with data from ultraviolet observations of new insights. So you could determine its nature by examining the ionized by the solar wind gas in the tail of comets. Furthermore, it was the composition of the atmospheres of planets - eg from Venus - are explored in more detail.