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

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<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu Coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>

Number of Results: 13048 Search : far
valve
  دریچه، سوپاپ   
daricé, supâp

Fr.: valve, soupape   

Any device that halts or regulates the flow of a fluid through a passage, pipe, etc.

From L. valvae "leaves of a door."

Daricé, leterally "small door, window," → stop. Supâp, loan from Fr. soupape, from O.Fr. sourpape, probably from souspape "a blow under chin," from sous "under," from L. subtus, → sub-, + *pape "jaw," from paper, from L. pap(p)are "to eat."

valve mechanism
  ساز-و-کار ِ سوپاپ   
sâzokâr-e supâp

Fr.: mécanisme de valve   

A mechanism proposed by Eddington to explain → stellar pulsations. Same as the → kappa mechanism. In this analogy the stellar layer acts like a heat engine with radiation taking the role of stream. The expanding and contracting layer acts as the piston, and the opacity of the layer behaves as the valve mechanism (Eddington, 1917, The pulsation theory of → Cepheid variables, The Observatory 40, 290).

valve; → mechanism.

Van Allen belts
  کمربندهای ِ وان آلن   
kamarbandhâ-ye Van Allen

Fr.: ceintures de Van Allen   

The ring-shaped regions of charged particles surrounding the Earth from 1 to 6 Earth radii into space. The charged particles are trapped in by the Earth's magnetic field. The inner belt is between 1.2 and 4.5 Earth radii and contains high-energy electrons and protons which originate mainly from interactions between cosmic rays and the upper atmosphere. The outer belt, located between 4.5 and 6.0 Earth radii, contains lower-energy charged particles mainly coming from the solar wind.

Named after James Van Allen (1914-2006), who discovered the belts in 1958 based on measurements made by Explorer 1, the USA's first successful artificial satellite; → belt.

Van Cittert-Zernike theorem
  فربین ِ فان سیترت-زرنیکه   
van farbin-e Cittert-Zernike

Fr.: théorème de Cittert-Zernike   

In → Young's experiment of → interference with double apertures, if a monochromatic source is a considerable distance from the → aperture plane and aperture separation is small, → fringe visibility from an extended source is proportional to the → Fourier transform of the source's spatial distribution. The transform variable is the angular separation of the aperture-plane sampling points divided by the wavelength. The van Cittert-Zernike Theorem is at the heart of → aperture synthesis.

Developed independently by Dutch physicists Pieter Hendrick van Cittert (1889-1959) in 1934 and Frits Zernike (1888-1966) in 1939; → theorem.

van den Bergh catalogue (vdB)
     
kâtâlog-e van den Bergh

Fr.: catalogue de van den Bergh   

A catalog of → reflection nebulae containing 158 objects. The catalog gives information for all BD and CD stars north of δ = -33 deg which are surrounded by reflection nebulosity visible on both the blue and red prints of the → Palomar Observatory Sky Survey .

van den Bergh, S., 1966, AJ, 71, 990; → catalog

van der Waals equation
  هموگش ِ وان در والس   
hamugeš-e van der Waals

Fr.: équation de van der Waals   

An → equation of state that satisfactorily describes the behavior of → real gass over a wide range of temperatures and pressures. It is derived from considerations based on kinetic theory, taking into account to a first approximation the size of a molecule and the cohesive forces between molecules: (P + a / V2) (V - b) = RT, where P, V, and T are pressure, volume, and temperature and R the gas constant. a and b are characteristic constants for a given substance. For a = b = 0, the van der Waals equation reduces to the characteristic equation of an → ideal gas. See also → Dieterici equation.

Named after Dutch physicist Johannes Diderik van der Waals (1837-1923), Nobel Prize in Physics 1910; → equation.

van der Waals force
  نیروی ِ وان در والس   
niru-ye van der Waals

Fr.: force de van der Waals   

A weak attractive force between neutral atoms and molecules arising from polarization induced in each particle by the presence of other particles. All molecules contain electrically charged particles, and even though the molecule as a whole is electrically neutral there do exist between molecules van der Waals attractive forces of electric origin.

Named after Dutch physicist Johannes Diderik van der Waals (1837-1923), Nobel Prize in Physics 1910; → force.

vanadium
  وانادیوم   
vânâdiom (#)

Fr.: vanadium   

A soft, ductile, silver-grey metal; symbol V. → Atomic number 23; → atomic weight 50.9415; → melting point about 1,890°C; → boiling point 3,380°C; → specific gravity about 6 at 20°C; and → valence +2,+3, +4, or +5. → It is used in various alloys to increase its shock resistance.

Named 1830 by Swedish chemist Nils Gabriel Sefström (1787-1845), from Old Norse Vanadis, epithet of the goddess Freya, + → -ium.

vane
  ۱، ۲) پره؛ ۳) بادنما   
1, 2) parré (#); 3) bâdnemâ (#)

Fr.: 1) aile, pale; 2) barbe; 3) girouette   

1) A blade attached radially to a central axis, as in a windmill, propeller, revolving fin, or the like. → spider vane.
2) → wind vane.
3) The flat part of a bird's → feather.

M.E., from O.E. fana "flag;" cognate with Ger. Fahne "flag," Gothic fana "piece of cloth."

Parré, from parr, → feather.

vanish
  ونیدن   
venidan

Fr.: 1, 2) disparaître, se volatiser; 3) s'en aller   

1) To disappear from sight, especially quickly; become invisible.
2) To disappear by ceasing to exist; come to an end.
3) Math.: To become zero or to tend to zero.

M.E., from O.Fr. esvanir "disappear; cause to disappear," from L. evanescere "disappear, pass away, die out," from → ex- "out" + vanescere "to vanish," from vanus "empty," cognate with O.E. wanian "to lessen," wan "deficient;" O.N. vanta "to lack;" L. vacare "to be empty," vastus "empty, waste;" see below for Iranian cognates.

Venidan, from Kurd. ven "missing; away; absent," cf. Pers. vang "empty, empty-handed, poor;" related to Av. ūna- "deficient, empty," ū- "to be incomplete;" akin to Skt. vā- "to disappear, diminish," ūná- "deficient;" L. vanus "empty," as above.

vanquish
  وانیدن   
vânidan

Fr.: vaincre   

1) To → conquer or subdue by superior force, as in battle.
2) To defeat in any contest or conflict; be victorious over (Dictionary.com).

O.Fr. venquis-, extended stem of veintre "to defeat," from L. vincere "to overcome, conquer."

Vânidan, from Mid.Pers. vânidan "to vanquish, to conquer;" cf. Av. van- "to vanquish, to defeat;" Skt. van- "to win, conquer;" O.E. winnan, E. win, PIE *uen- "to win, conquer."

vapor
  بخار   
boxâr (#)

Fr.: vapeur   

The gaseous form of substances that are normally in liquid or solid form.

M.E. vapour, L. vapor "exhalation, steam, heat," of unknown origin.

Boxâr, loan from Ar. buxâr.

vaporization
  بخارش   
boxâreš

Fr.: vaporisation, évaporation   

The act of vaporizing. The state of being vaporized.
The rapid change of water into steam.

Verbal noun of → vaporize.

vaporize
  ۱) بخاریدن؛ ۲) بخاراندن   
1) boxâridan; 2) boxârândan

Fr.: 1) s'évaporer; 2) évaporer   

1) To become converted into vapor.
2) To cause to change into a vapor.

vapor + → -ize.

variability
  ورتندگی   
vartandegi

Fr.: variabilité   

The quality, state, or degree of being variable or changeable.

Quality noun from → variable.

variability index
  دیشن ِ ورتندگی   
dišan-e vartandegi

Fr.: indice de variabilité   

A measure of variability of a star (such as Welch-Stetson variability index) which combines the information from two passbands assuming that changes in the star's luminosity occur nearly simultaneously at all optical wavelengths.

variability; → index.

variable
  ورتنده   
vartandé

Fr.: variable   

Something that may or does vary. → variable star.
Math.: A symbol, usually a letter, which in a mathematical or logic expression represents any member of a set of possible values or possible objects.

M.E., from O.Fr. variable, from L. variabilis "changeable," from variare "to change," → vary.

Vartandé agent noun from vartidan "to change," → vary.

variable star
  ستاره‌ی ِ ورتنده   
setâre-ye vartandé

Fr.: étoile variable   

A star whose luminosity changes over periods of time; there are many reasons and many types. → cataclysmic variable; → Cepheid; → pulsating star; → nova; → long-period variable; → short-period variable; → Luminous Blue Variable (LBV); etc.

variable; → star.

variable star designation
  نامگزینی ِ ستاره‌ی ِ ورتنده   
nâmgozini-ye setâre-ye vartandé

Fr.: designation des étoiles variables   

A set of conventions used for naming → variable stars. Stars with existing → Bayer designations are not given new designations. Alternatively, the letters R through Z are used followed by the Latin genitive of the name of the hosting constellation. Otherwise, two letters of alphabet are used (334 combinations) with the Latin genitive of the name of the constellation. Finally, the letter V (variable) is used followed by numbers 335, 336, and so on. Some examples are: → P Cygni, → T Tauri, → FU Orionis, → EX Lupi, and → V2052 Oph.

variable; → star; → designation.

variance
  ورتایی   
vartâyi

Fr.: variance   

A measure of the scatter of the values of a random variable (X) about its mean (μ). Var(X) = E(X -μ)2. The positive square root of the variance is called the → standard deviation.

M.E., from O.Fr. variance, from L. variantia, from variare "to change," → vary.

Vartâyi quality noun from vartâ agent noun from vartidan, → vary.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer AGB air Alf Alg all alp alt AM amo ana And ang ani ano Ant Ant apa apo app app Ara Arc ari Arr ash ass ast ast asy atm ato att aut ave axi Bab bal Bal bar bar bea Bek Bes bia Big bin bin bip biv bla bli blu Boh Bol Bos bou bra bri bro buo cal cal can cap car Car cat cat CCD Cen cen CH cha cha che Che chr cir cir cit cla clo clo clu Coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con Cop Cor cor cor cos cos cou cou Cow cre cri cro cry cur cya Cyg dan dar dat de- deb dec dec ded def deg del dem den dep des det dev dia dif dif dih dio Dir dis dis dis dis dis dis DO don dou dow dro dur dwa dyn Dys ear ebb ecl edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ esc eth Eur Eve exa exc exe exi exp exp ext ext ext fac fal far fed Fer fer fie fin fir fis fla flo flu fol for for fou fra fre Fre fro fut G-t gal gal gam gas Gau Gem gen geo geo geo gia Gli Gol gra gra gra gra gre gri gui H I Hag hal har hat He- hea hel Hel her Hes hie hig his hom hor hot Hub Hug hur hyd hyd hyg hyp ice ide ima Ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv Io ion iro isl iso iso Jac jet jud jur Kel Kep kil Klo Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Meg Mer Mer met met Met mic Mid Mil min Mir mit mod mod mol mon Mor mou mul mul mys nan Nat nau nec neo neu nev New NGC no nom non non nor not nuc nuc num nut obj obs obs occ ocu oft ome Oor ope opp opt opt orb ord ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per per pha phi pho pho pho phy pio Pla pla pla pla Pla plu Poi pol pol pol poo pos pos pot pra pre pre pre pre pri pri pro pro pro pro pro Pro pro pse pul pur qua qua qua qua que rac rad rad rad rad rad rad ran rar ray rea rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot Rus Sac sal sat sca sca Sch sci Scu sec sec Sed sel Sel sen ser Sex Sha she sho sid sig sil sim sin siz sla Sma sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spi spr squ sta sta sta sta ste ste ste Sto Str str str sub sub suc sun sup sup sup sup sur swa syn syn tab tar tek tem ter tes the the the the Tho thr tid tim Tis Too Tor tra tra Tra tra tra tri tri tru Tul tur two Typ ult un- und uni uni unk upp Urc utt val var vec vel ver vib vio vir vis voi vor wan wat wav wax wea Wei whi Wil win WN9 wor X-r yel you zer zod > >>