An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 33 Search : spectrum
absorption spectrum
  بیناب ِ درشمی   
binâb-e daršami

Fr.: spectre d'absorption   

A spectrum of absorption lines or bands, produced when light from a hot source, itself producing a continuous spectrum, passes through a cooler gas.

absorption; → spectrum.

angular power spectrum
  بیناب ِ توانی ِ زاویه‌ای   
binâb-e tavâni-ye zâviye-yi

Fr.: spectre de puissance angulaire   

Of the → cosmic microwave background radiation, a plot of how much the temperature varies from point to point on the sky versus the angular frequency. This spectrum answers fundamental questions about the nature of the Universe. → cosmic microwave background anisotropy; → dipole anisotropy.

angular; → power; → spectrum.

arc spectrum
  بیناب ِ کمان   
binâb-e kamân

Fr.: spectre d'étincelle   

The spectrum produced by an atom or mixture of atoms as a result of vaporization within an electric arc generated between two electrodes.

arc; → spectrum.

band spectrum
  بیناب ِ باندی   
binâb-e bândi

Fr.: spectre de bande   

A spectrum which consists of a number of bands each having one sharp edge. Each band is composed of a large number of closely spaced emission or absorption lines. Band spectra are typical of molecules. Bands produced by titanium oxide, zirconium oxide, and carbon compounds are characteristic of low temperature stars.

Band spectrum, from → band + → spectrum.

Binâb-e bândi, from binâb, → spectrum + bândi, relating to bând, → band.

blackbody spectrum
  بیناب ِ سیه‌جسم   
binâb-e siyah-jesm (#)

Fr.: spectre de corps noir   

A curve displaying → blackbody radiation intensity versus the wavelength for a given temperature, according to → Planck's blackbody formula. It is an asymmetrical curve with a sharp rise on the short wavelength side and a much more gradually sloping long-wavelength tale. Same as → Planck spectrum.

blackbody; → spectrum.

CMB angular power spectrum
  بیناب ِ توانی ِ زاویه‌ای ِ CMB   
binâb-e tavâni-ye zâviye-yi-e CMB

Fr.: spectre de puissance angulaire du CMB   

A plot displaying the amplitude of → cosmic microwave background anisotropy as a function of angular size or → multipole index. Same as → angular fluctuation spectrum. The plot, based the on WMAP and other data, shows a plateau at large angular or length scales (→ Sachs-Wolfe plateau), then a series of peaks at progressively smaller scales. These features arise from the gravity-driven acoustic oscillations of the coupled photon-baryon fluid in the early Universe (→ baryon acoustic oscillation). In particular, a strong peak is seen on an angular scale (at l ~220), corresponding to the physical length of the → sound horizon at the → recombination era. It depends on the curvature of space. If space is positively curved, then this sound horizon scale will appear larger on the sky than in a flat Universe (the first peak will move to the left). The second peak (l ~ 550), which is the first harmonic of the main peak, relates to the baryon/photon ratio. The third peak can be used to help constrain the total matter density.

angular; → fluctuation; → spectrum.

comparison spectrum
  بیناب ِ هم‌سنجش   
binâb-e hamsanješ

Fr.: spectre de comparaison   

A spectrum of known substances used as a standard of comparison for investigating spectra of celestial objects.

comparison; → spectrum.

composite spectrum
  بیناب ِ همنهاده   
binâb-e hamnehâdé

Fr.: spectre composite   

A stellar spectrum displaying lines characterising two stars of different types.

composite; → spectrum.

continuous spectrum
  بیناب ِ پیوسته   
binâb-e peyvasté

Fr.: spectre continu   

An electromagnetic spectrum in which emitted or absorbed radiation is present continuously over all wavelengths in a given range.

continuous; → spectrum.

Binâb, → spectrum; peyvastécontinuous.

discrete spectrum
  بیناب ِ گسسته   
binâb-e gosasté

Fr.: spectre discret   

A spectrum in which the component wavelengths (and wave numbers and frequencies) constitute a discrete sequence of values (finite or infinite in number) rather than a continuum of values.

discrete; → spectrum.

electromagnetic spectrum
  بیناب ِ برقامغناتی   
binâb-e barqâmeqnâti

Fr.: spectre électromagnétique   

The range of frequencies over which electromagnetic waves are propagated. → electromagnetic radiation.

electromagnetic; → spectrum.

emission spectrum
  بیناب ِ گسیلی   
binâb-e gosili (#)

Fr.: spectre d'émission   

A spectrum consisting of emission lines, produced when the light does not undergo absorption between the source and the spectrograph.

emission; → spectrum.

energy spectrum
  بیناب ِ کاروژ   
binâb-e kâruž

Fr.: spectre d'énergie   

Of cosmic rays, the plot representing the number of particles as a function of their energy.

energy; → spectrum.

first-order spectrum
  بیناب ِ رایه‌ی ِ نخست   
binâb-e râye-ye naxost

Fr.: spectre du premier ordre   

An optical spectrum, produced by a diffraction grating, in which the difference in path length of light from adjacent slits is one wavelength.

first; → order; → spectrum.

flash spectrum
  بیناب ِ درخشی   
binâb-e deraxši

Fr.: spectre-éclair   

The spectrum of the solar → chromosphere obtained during a → solar eclipse in the instant before or after → totality. In the flash spectrum the usual solar → absorption lines are replaced with bright → emission lines. This is because in that very short interval only the → photosphere is eclipsed by the Moon, and not the chromosphere. The American astronomer Charles A. Young was the first to observe it during the the solar eclipse of 1870 (December 22) in Spain.

The flash designation comes from the fact that the change from dark-line to bright-line spectrum is very rapid; → flash; → spectrum.

frequency spectrum
  بیناب ِ بسامد   
binâb-e basâmad

Fr.: spectre de fréquence   

A graphical display of the intensity of radiation or energy versus frequency.

frequency; → spectrum.

Kolmogorov spectrum
  بیناب ِ کولموگوروف   
binâb-e Kolmogorove

Fr.: spectre de Kolmogorov   

The distribution of energy over different scales in a → turbulent flow where → energy cascade occurs. Let E be the energy per unit → wave number (k) and ε the energy → dissipation parameter, E = E(k,ε). → Dimensional analysis yields: E = Cε2/3k-5/3, where C is the → Kolmogorov constant.

A. N. Kolmogorov, 1941, Local structure of turbulence in an incompressible fluid for very large Reynolds numbers, Doklady Acad Sci. USSR 31, 301; → spectrum.

line spectrum
  بیناب ِ خطی   
binâb-e xatti (#)

Fr.: spectre de raies   

Spectrum consisting of discrete lines (emission or absorption), each corresponding to a particular wavelength, as opposed to a continuous spectrum.

line, → spectrum.

mass spectrum
  بیناب ِ جرم   
binâb-e jerm (#)

Fr.: spectre de masse   

A spectrum of charged particles, arranged in order of mass or mass-to-charge ratios. → mass spectrometry.

mass; → spectrum.

mean spectrum
  بیناب ِ میانگین   
binâb-e miyângin

Fr.: spectre moyen   

A plot of the mass-to-charge ratio of elementary particles, sorted by their isotopic mass.

mean; → spectrum.

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