Ultraviolet astronomy

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The ultraviolet astronomy devoted to the study of astronomical objects in the ultraviolet radiation (UV). In astronomy , electromagnetic radiation with a wavelength between about 10 and 380 nanometers (nm) is called ultraviolet. This wavelength range is generally further subdivided into the near UV (NUV, 200 to 380 nm), the far UV (FUV, 100 to 200 nm) and the extreme UV (EUV, 10 to 100 nm). X-ray astronomy follows the UV range in the short-wave range.


Since a large part of the UV radiation is already absorbed in the stratosphere , mainly by the oxygen or ozone , observation by ground stations - even from mountains - is not possible. Initially, measurements in the near UV range up to about 200 nm wavelength were carried out from research balloons, which could penetrate to heights of about 45 km. From 1962, the eight Orbiting Solar Observatory satellites made it possible to use satellites for observation, although these only served to observe the sun . From 1972, Copernicus and similar European satellites also made it possible to observe other objects, including in the UV range. However, ultraviolet astronomy only gained in importance when the International Ultraviolet Explorer (IUE) was available for almost two decades from 1978 to 1996 , and the Hubble space telescope also has UV instruments on board and enabled the results to be improved again. In 2003 another satellite for observation in the ultraviolet was launched with GALEX . This gave the researchers access to light with wavelengths down to 105 nm, thanks to the special mirror coating from Copernicus. Conventional coatings on the mirrors used in high-performance telescopes become opaque below 160 nm . That is why a coating made of LiF was chosen for this satellite , but it is hygroscopic and therefore caused difficulties in the humid climate of Florida before take-off. Further penetration into areas of shorter wavelengths of up to 10 nm is only possible with a grazing incidence of light on the telescope's mirrors .


Among other things, the UV range is particularly suitable for examining hot stars that radiate intensely in the UV. There are also types of extragalactic objects with intense UV radiation. In addition to the objects themselves, the interstellar matter between the earth and the observed object can also be examined well, as there are numerous interstellar absorption lines in the UV range . This absorbs the radiation below 91.2 nm wavelength very strongly, because at this energy the hydrogen is ionized in the H-II areas . These areas are again permeable to light with wavelengths of around 10 nm - an area that still needs to be explored. In contrast to the other modern branches of astronomy, such as X-ray , radio and infrared astronomy , UV astronomy did not primarily discover novel objects such as X-ray sources or cold protostars . Rather, it is operated using the methods of optical astronomy and primarily spectroscopic investigations are carried out on the physical composition or radial velocity, especially of hot stars. The advantage over optical astronomy lies in the large number of spectral lines in this wavelength range, including those elements that are common in the universe, such as the well-known Lyman series . With the help of ultraviolet astronomy, it was possible to learn significantly more about gas flows around hot stars and in binary star systems . But also within our solar system , data from ultraviolet observations could be used to gain new knowledge. By examining the gas ionized by the solar wind in the tail of comets, it was possible to determine their nature. Furthermore, the composition of the atmospheres of planets - z. B. from Venus - be explored more closely.

Ultraviolet space telescopes launched so far

designation year Remarks
Orbiting Solar Observatory OSO-1 to OSO-8 1962-1988 8 satellites for solar observation
Orbiting Astronomical Observatory 3 (Copernicus) 1972-1981
Astronomical Nederlandse Satelliet (ANS) 1974-1977 Also x-ray telescope
International Ultraviolet Explorer (IUE) 1978-1996
Astron 1983-1989
Hopkins Ultraviolet Telescope (HUT) 1990 and 1995 Part of the shuttle missions Astro-1 and -2
Ultraviolet Imaging Telescope (UIT) 1990 and 1995 Part of the shuttle missions Astro-1 and -2
Wisconsin Ultraviolet Photo-Polarimeter Experiment (WUPPE) 1990 and 1995 Part of the shuttle missions Astro-1 and -2
ROSAT 1990-1999 Mainly X-ray astronomy
Hubble Space Telescope (HST) Since 1990 Also for visible light and near infrared
Solar and Heliospheric Observatory (SOHO) since 1995 Solar observation, also other wavelength ranges
Extreme Ultraviolet Explorer (EUVE) 1992-2001
ORFEUS 1993 and 1996 Part of the shuttle missions STS-51 and -80
TRACE 1998-2010 Solar observation
Far Ultraviolet Spectroscopic Explorer (FUSE) 1999-2007
CHIPSat 2003-2008
Galaxy Evolution Explorer (GALEX) since 2003
Swift since 2004 Localization of gamma-ray flashes , including X-rays and visible light


  • Lars L. Christensen, et al .: Hidden Universe. Wiley-VCH, Weinheim 2009, ISBN 978-3-527-40868-9 .
  • Martin A. Barstow, et al .: Extreme ultraviolet astronomy. Cambridge University Press, Cambridge 2003, ISBN 0-521-58058-7 .
  • George Sonneborn: Astrophysics in the far ultraviolet. Astronomical Society of the Pacific, San Francisco 2006, ISBN 1-58381-216-4 .
  • JE Drew: New developments in x-ray and ultraviolet astronomy. Pergamon Press, Oxford 1995, ISBN 0-08-042623-9 .
  • Jon A. Morse: Ultraviolet optical space astronomy beyond HST. Astronomical Soc. of the Pacific, San Francisco 1999, ISBN 1-886733-85-6 .

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