An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

Number of Results: 9 Search : ultraviolet
extreme ultraviolet (EUV)
  فرابنفش ِ استوم   
farâbanafš-e ostom

Fr.: ultraviolet extrême   

A part of the ultraviolet radiation with wavelengths between 50 and 300 Angstöms.

extreme; → ultraviolet.

far ultraviolet (FUV)
  فرابنفش ِ دور   
farâbanafš-e dur (#)

Fr.: ultraviolet lointain   

Ultraviolet radiation in the wavelength range 912-2000 Å. See also → extreme ultraviolet.

far; → ultraviolet.

International Ultraviolet Explorer (IUE)
     

Fr.: IUE   

A satellite dedicated to spectroscopic observations of astronomical objects in ultraviolet wavelengths, launched in 1978. It was an international collaboration between → NASA, the → European Space Agency (ESA), and the United Kingdom's Science and Engineering Research Council. It operated until September 1996 and collected over 70,000 spectra. IUE consisted of a 45-cm telescope (f/15) equipped with two spectrographs operating in the ranges 1850-3300 Å and 1150-2000 Å. Each spectrograph had a high-resolution and a low-resolution mode with resolutions of about 0.2 Å and 6 Å respectively.

international; → ultraviolet; → explorer.

near ultraviolet
  فرابنفش ِ نزدیک   
farâbanafš-e nazdik (#)

Fr.: proche ultraviolet   

The longest wavelengths of the ultraviolet region, which are adjacent to the visible, from 200 to 350 nm.

near; → ultraviolet.

ultraviolet (UV)
  فرابنفش، اولتر-بنفش   
farâ-banafš, ultar-banafš

Fr.: ultraviolet   

The part of the electromagnetic radiation beyond the violet end of the visible spectrum with wavelengths approximately in the range 50 Å to 4,000 Å. → extreme ultraviolet; → far ultraviolet.

ultra-; → violet.

ultraviolet astronomy
  اخترشناسی ِ فرابنفش، ~ اولتر-بنفش   
axtaršenâsi-ye farâ-banafš, ~ ultar-banafš

Fr.: astronomie ultraviolette   

The study of astronomical objects in the ultraviolet portions of the electromagnetic spectrum, in the waveband 3000 Å to about 10 Å. At these wavelengths, the atmosphere prevents ultraviolet radiation from reaching the Earth surface. Therefore ground-based observatories cannot observe in the ultraviolet. Only with the advent of space-based telescopes has this area of astronomy become available for research.

ultraviolet; → astronomy.

ultraviolet catastrophe
  نگونزار ِ فرابنفش   
negunzâr-e farâbanafš

Fr.: catastrophe ultraviolette   

A paradox encountered in the classical theory of thermal radiation (→ Rayleigh-Jeans law), whereby a → blackbody should radiate an infinite amount of energy at infinitely short wavelengths, in contradiction with what is observed. The problem was solved by Max Planck in 1900, who suggested that, rather than being continuous, the energy comes in discrete parcels called quanta. The avoidance of the ultraviolet catastrophe was one of the first great achievements of → quantum mechanics.

This problem was first raised by Lord Rayleigh (1842-1919), whereas the term ultraviolet catastrophe was first used by Paul Ehrenfest (1880-1933); → ultraviolet; → catastrophe.

ultraviolet excess
  فزونی ِ فرابنفش، فرهبود ِ اولتر-بنفش   
fozuni-ye farâbanafš, ferehbud-e ultar-banafš

Fr.: excès ultraviolet   

Ultraviolet emission from an object in excess of that expected for a reference. For example, → subdwarf stars show ultraviolet excess with respect to that expected from a star with → solar metallicity at a given → effective temperature. In this case, UV excess results from smaller → line blanketing in → population II stars.

ultraviolet; → excess.

ultraviolet star
  ستاره‌ی ِ فرابنفش، ~ ِ اولتر-بنفش   
setâre-ye farâbanafš, ~ ultar-banafš

Fr.: étoile ultraviolette   

A star, such as O types or hot central stars of planetary nebulae, which radiates essentially in the ultraviolet part of the electromagnetic spectrum.

ultraviolet; → star.