An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 11 Search : d line
blend lines
  خطهای ِ توهم، تانهای ِ ~   
xatthâ-ye tuham, tânhâ-ye ~

Fr.: raies mélangées   

Spectral lines intermingled.

blend; → line.

D line
  خط ِ D   
xatt-e D

Fr.: raie D   

One of the pair of yellow lines in emission spectra of neutral sodium (Na I). D1 has a wavelength of 5895.94 Å and D2 is 5889.97 Å. This sodium doublet is one of the strongest absorption features in the spectra of late-type stars.

Labelled D in a sequence of alphabetical letters first used by Joseph von Fraunhofer to designate spectral features in the solar spectrum, → Fraunhofer line.

frozen magnetic field line
  خط ِ میدان ِ مغناتیسی ِ یخ‌بسته، ~ ~ ~ رچیده   
xatt-e meydân-e meqnâtisi-ye yax basté, ~ ~ ~ rocidé

Fr.: ligne de champ magnétique gelée   

A → magnetic field line in a → fluid when the motion of the fluid carries the magnetic field along with it.

Frozen, p.p. of → freeze; → magnetic; → line.

magnetic field line
  خط ِ میدان ِ مغناتیسی   
xatt-e meydân-e meqnâtisi (#)

Fr.: ligne de champ magnétique   

An imaginary line used for representing the strength and direction of a magnetic field. Charged particles move freely along magnetic field lines, but are inhibited by the magnetic force from moving across field lines.

magnetic; → field; → line.

open magnetic field line
  خط ِ باز ِ میدان ِ مغناتیسی   
xatt-e bâz-e meydân-e meqnâtisi-ye

Fr.: ligne ouverte de champ magnétique   

In the context of solar physics, a → magnetic field line when it crosses the solar surface only once, i.e., when it goes from surface to infinity. This is the case at a sufficiently large scale in → coronal holes. This is mostly not the case in → active regions.

open; → magnetic; → field; → line.

permitted line
  خط ِ پرزامیده   
xatt-e parzâmidé

Fr.: raie permise   

An ordinary spectral line emitted by atoms undergoing energy transitions that are allowed by the selection rules of quantum mechanics. → forbidden lines.

permitted; → line.

redshifted line
  خط ِ سرخ‌کیبیده   
xatt-e sorx kibideh

Fr.: raie décalée vers le rouge   

A spectral line whose wavelength does not coincide with its theoretical value and is shifted toward longer wavelengths.

red; → shift; → line.

resolved line
  خط ِ واگشوده   
xatt-e vâgošudé

Fr.: raie résolue   

A → spectral line that is not contaminated by other nearby lines.

resolved; → line.

thermalized line
  خط ِ یکگرماییده   
xatt-e yekgarmâyidé

Fr.: raie thermalisée   

A collisionally excited spectral line formed in high density condition well above the → critical density. At such densities the → excitation temperature is at (or very near) the → kinetic temperature of the gas. At low densities, below the critical density, the excitation temperature will be only slightly above the radiation temperature and the emission line will be practically invisible.

Thermalized, p.p. of → thermalize; → line.

unidentified line
  خط ِ نا-ایدانیده   
xatt-e nâ-idânidé

Fr.: raie non identifiée   

A spectral line whose origin is not clearly established. → line identification.

unidentified; → line.

world line
  خط ِ جهان، جهان-خط   
xatt-e jahân, jahân-xatt (#)

Fr.: ligne d'univers   

In relativity, the path traced out in four-dimensional → space-time that represents a continuous sequence of events relating to a given particle. A point on a world line is called an → event. Any straight world line corresponds to an → inertial motion. Curved world lines represent → accelerated motion. A world line that curves corresponds to an accelerated observer. World lines are shown on space-time diagrams.

world; → line.