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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extinction stars
  ستارگان ِ خاموشی   
setâregân-e xâmuši

Fr.: étoiles d'extinction   

Stars specifically observed at selected air masses in view of determining the atmospheric extinction coefficients.

extinction; → star.

extraction
  برهنجش   
barhanješ

Fr.: extraction   

1) The act of extracting or the condition of being extracted.
2) Something obtained by extracting; an extract (FreeDictionary.com).

extract; → -tion.

extragalactic astronomy
  اخترشناسی ِ استرکهکشانی، ~ برون‌کهکشانی   
axtaršenâi-ye ostar-kahkašâni, ~ borun-kahkašâni

Fr.: astronomie extragalactique   

The branch of astronomy that deals with objects beyond the Milky Way, especially galaxies and quasars.

extragalactic; → astronomy.

extrapolation
  برون‌یابش   
borunyâbeš (#)

Fr.: extrapolation   

Predicting the value of unknown data points by projecting a function beyond the range of known data points.

Verbal noun of → extrapolate.

extreme horizontal branch star (EHB)
  ستاره‌ی ِ شاخه‌ی ِ افقی ِ استوم   
setâre-ye šâxe-ye ofoqi-ye ostom

Fr.: étoile de la branche horizontale extrême   

The hottest variety of stars on the → horizontal branch with temperatures ranging from 20,000 to 40,000 K. EHB stars are distinguished from normal horizontal branch stars by having extremely thin, inert hydrogen envelopes surrounding the helium-burning core. They are hot, dense stars with masses in a narrow range near 0.5 Msun. These stars have undergone such extreme mass loss during their first ascent up the giant branch that only a very thin hydrogen envelope survives. Stars identified as EHB stars are found in low metallicity globular clusters as an extension of the normal HB.

extreme; → horizontal; → branch; → star.

extrinsic photoconductivity
  شیدهازندگی ِ برونگین   
šidhâzandegi-ye borungin

Fr.: photoconductivité extrinsèque   

Photoconductivity due to the addition of impurities or external causes.

extrinsic; → photoconductivity.

Šidhâzandegi, → photoconductivity; borungin, → extrinsic.

extrinsic semiconductor
  نیم‌هازا‌ی ِ برونگین   
nimhâzâ-ye borungin

Fr.: semiconducteur extrinsèque   

A semiconductor, such as silicon, whose responsive properties can be altered by the addition of impurities. Copper- and mercury-doped germanium are both examples of this semiconductor material.

extrinsic; → semiconductor.

F corona
  تاج ِ F   
tâj-e F

Fr.: couronne F   

The exterior part of the → solar corona, illuminated by solar light scattered or reflected by dust particles. The same phenomenon also produces the → zodiacal light, much farther away from the Sun. The dust particles are at most several microns in size and make up a disk stretching over almost 1 solar radius (700,000 km) from the Sun's surface. Unlike electrons, which are responsible for the → K corona, the dust particles move relatively slowly. Thus, the light scattered by them has the same spectrum as the → photosphere and shows the → Fraunhofer lines. The F corona is the most luminous part of the corona at 1.5 solar radii from the Sun's surface (M.S.: SDE).

F referring to the Fraunhofer lines; → corona.

Faber-Jackson relation
  بازانش فیبر-جکسون   
bâzâneš-e Faber-Jackson

Fr.: relation Faber-Jackson   

An empirical power-law correlation between the luminosity (L) and the velocity dispersion of stars (σ) in the center of a elliptical galaxies. The original relation can be expressed mathematically as: L ∝ σγ, where the index γ is observed to be approximately equal to 4, but depends on the range of galaxy luminosities that is fitted. → Tully-Fisher relation.

After the astronomers Sandra M. Faber and Robert Earl Jackson, who first noted this relation in 1976 (ApJ 204, 668); → relation.

fabulation
  افسانه‌بافی   
afsâné-bâfi (#)

Fr.: fabulation, affabulation   

1) To tell invented stories; create fables or stories filled with fantasy.
2) To relate an event as a fable.

fabulate; → -tion.

face-on galaxy
  کهکشان ِ رونما   
kahkešân-e runemâ

Fr.: galaxie vue de face   

A → spiral galaxy oriented such that it is viewed from above or below. → edge-on galaxy.

face; → on-; → galaxy.

facilitation
  آسانش   
âsâneš

Fr.: facilitation   

The act or process of facilitating.

facilitate; → -tion.

family of distributions
  خانواده‌ی ِ واباژش‌ها   
xânevâde-ye vâbâžešhâ

Fr.: famille de distributions   

A set of distributions which have the same general mathematical → formula.

family; → distribution.

Fanaroff-Riley classification
  رده‌بندی ِ فاناروف-رایلی   
radebandi-ye Fanaroff-Riley

Fr.: classification Fanaroff-Riley   

A classification scheme for distinguishing a → radio galaxy from an → active galaxy based on their → radio frequency  and → luminosity and their kpc-scale appearance. Analyzing a sample of 57 radio galaxies from the → 3CR catalogue, which were clearly resolved at 1.4 GHz or 5 GHz, Fanaroff & Riley (1974) discovered that the relative positions of regions of high and low → surface brightness in the → lobes of extragalactic → radio sources are correlated with their radio luminosity. They divided the sample into two classes using the ratio RFR of the distance between the regions of highest surface brightness on opposite sides of the central galaxy or quasar, to the total extent of the source up to the lowest brightness contour in the map. → Fanaroff-Riley Class I (FR-I) , → Fanaroff-Riley Class II (FR-II). The boundary between the two classes is not very sharp, and there is some overlap in the luminosities of sources classified as FR-I or FR-II on the basis of their structures. The physical cause of the FR-I/II dichotomy probably lies in the type of flow in the → radio jets.

Bernard L. Fanaroff and Julia M. Riley, 1974, MNRAS 167, 31P; → classification.

Faraday rotation
  چرخش ِ فارادی   
carxeš-e Faraday (#)

Fr.: rotation Faraday   

The rotation of the plane of → polarization experienced by a beam of → linearly polarized radiation when the radiation passes through a material containing a magnetic field with a component in the direction of propagation. This effect occurs in → H II regions in which a magnetic field causes a change in the polarized waves passing through. Same as → Faraday effect.

farad; → rotation.

Faraday's law of induction
  قانون ِ درهازش ِ فارادی   
qânun-e darhazeš-e Faraday

Fr.: loi d'induction de Faraday   

The induced → electromotive force in a circuit is equal in magnitude and opposite in sign to the rate of change of the → magnetic flux through the surface bounded by the circuit. Mathematically, it is expressed as: ∇ x E = -∂B/∂t, which is one of the four → Maxwell's equations.

farad; → law; → induction.

fecundation
  گشنش، گشن‌گیری، بارورسازی   
gošneš, gošngiri (#), bârvarsâzi (#)

Fr.: fécondation   

Biology: The act or process of fecundating.

fecundate; → -tion.

federation
  هیاوش   
hiâyveš

Fr.: fédération   

1) The act of federating or uniting in a league.
2) A political unit formed from smaller units on a → federal basis.

Verbal noun of → federate.

Fermi constant
  پایای ِ فرمی   
pâyâ-ye Fermi

Fr.: constante de Fermi   

The → coupling constant associated with the → weak interaction, which gives rise to → beta decay. CF = 1.167 x 10-5 GeV-2.

Fermi; → constant.

Fermi interaction
  اندرژیرش ِ فرمی   
andaržirš-e Fermi

Fr.: interaction de Fermi   

An old explanation, proposed by Enrico Fermi, of the → weak interaction.

fermi; → interaction.

<< < "no abe acc act aff ama ani ant aps ast atm aut bar bif Boh bou cal car Cen chi Cla col com com Com con con con con con con con con con con con con cor cor Cou cur dec def Den det dif dim dis dis dou E-t edi ele ell ene ero exa exp ext fer Fla fra FU Gam geo gra gra had har hig Hub Hyp imp ind inf ins int int ion iro ite Kep lar lep lin lon lun mag mas mer mig mol Moo mut neg new New non non non nuc obs on- opt Ori oxi par per per phl pho Pla ple pol pos pre Pro pro pub qua rad rad rec red reg rem res rev rot Sak Sco sec seg sha sim sol sou sph sta ste Str sub sup T a the Tho tra tre tum uni vel vis wav wor > >>