An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 716
de Broglie equation
  هموگش ِ دوبروی   
hamugeš-e de Broglie

Fr.: équation de de Broglie   

According to the → de Broglie hypothesis, which has been verified by experiments, every → particle of matter, whatever its nature, has a characteristic → wavelength associated with its wavelike quantum aspect. The de Broglie equation gives the equivalent wavelength of a moving particle: λ = h/mv, where h is → Planck's constant, m the mass of the particle, and v its velocity.
See also: → de Broglie wavelength, → Davisson-Germer experiment.

Named after Louis Victor de Broglie (1892-1987), French physicist, creator of a new field in physics, wave mechanics, who won the Nobel prize in physics in 1929. → equation

de Broglie hypothesis
  انگاره‌ی ِ دوبروی   
engâre-ye de Broglie

Fr.: hypothèse de de Broglie   

The suggestion by Louis de Broglie in 1924 whereby if → electromagnetic waves possess particle properties (→ particle nature), then it might be reasonable to suppose that material particles, such as → electrons, should possess wave properties (→ wave nature). The de Broglie hypothesis was based on the intuitive feeling that nature seems to have strong attachment to symmetry. In other words, if radiation has particle-like properties, then material particles should possess wave-like properties. At the time no direct experimental evidence was present for the validity of this suggestion. The first confirmation of de Broglie's hypothesis was provided by the → Davisson-Germer experiment. See also → wave-particle duality;

de Broglie equation; → hypothesis.

de Broglie wavelength
  موج-طول ِ دوبروی   
mowjtul-e de Broglie

Fr.: longueur d'onde de Broglie   

The wavelength of the wave associated with a → particle as given by the → de Broglie equation.

de Broglie equation; → wavelength.

de Sitter Universe
  گیتی ِ دوسیتر   
giti-ye de Sitter

Fr.: Univers de de Sitter   

A solution to → Einstein's field equations of → general relativity which contains no ordinary matter (ΩM = 0) or radiation (ΩR = 0), is → Euclidean (k = 0), but has a → cosmological constantΛ > 0). The Universe expands exponentially forever. This solution was the first model expanding of → expanding Universe. See also → empty Universe, → Milne Universe.

After the Dutch mathematician and physicist Willem de Sitter (1872-1934) who worked out the model in 1917; → universe.

de Vaucouleurs law
  قانون ِ دووکولور   
qânun-e de Vaucouleurs

Fr.: loi de Vaucouleurs   

A mathematical expression describing the → surface brightness profile of a typical → elliptical galaxy, whereby the projected luminosity distribution varies as exp(-R)1/4.

de Vaucouleurs radius; → law.

de Vaucouleurs radius
  شعاع ِ دووکولور   
šo'â'-e de Vaucouleurs

Fr.: rayon de Vaucouleurs   

An → isophotal radius of a galaxy, where the → surface brightness in the B band falls to 25 mag arcsec-2.

After the French-born American astronomer Gérard de Vaucouleurs (1918-1995); → radius.

  وا-، فرو-   
vâ- (#), foru- (#)

Fr.: de-   

A prefix occurring in loanwords from L. to indicate:
1) Opposition, reversal: decentralize, decode, deactivate, de-emphasis.
2) Removal from: dethrone.
3) Reduction, degradation: declass, devalue.
4) reversal: detract, detect.
5) Derivation from: derive, deverbative.

M.E., from O.Fr. de-, des-, partly from L. de- "from, down, away," and partly from L. → dis-.

Prefix vâ- denoting "reversal, opposition; separation; repetition; open; off; away," variant of bâz-, from Mid.Pers. abâz-, apâc-; O.Pers. apa- [pref.] "away, from;" Av. apa- [pref.] "away, from," apaš [adv.] "toward the back;" cf. Skt. ápāñc "situated behind."
Foru- "down, downward; below; beneath," Mid.Pers. frôt "down, downward," O.Pers. fravata "forward, downward," Skt. pravát- "a sloping path, the slope of a mountain."

  فرو انگیزش   

Fr.: désexcitation   

Transition from an excited energy state to a lower energy level, as in spectral line formation or particle emission from an atomic nucleus.

From → de- + → excitation.


Fr.: désorbiter   

To cause a spacecraft to leave its operational orbit to enter a descent phase or to change course.

From → de- + → orbit.


Fr.: désorbitage   

Of a spacecraft, the act or process of departing from an operational orbit. → de-orbit.

Noun form of → de-orbit.


Fr.: déprojection   

A method for estimating the real orientation of a field and/or related velocities/separations from two-dimensional images.

de-; → projection.


Fr.: dérougir   

To correct the intensity or flux of a spectral line by eliminating the → reddening effect of → interstellar dust.

De-redden, from → de- + redden verb of → red.

Vâsorxidan, from vâ-, → de-, + sorxidan verb of sorx, → red.

de-reddened magnitude
  برز ِ واسرخیده   
borz-e vâsorxidé

Fr.: magnitude dérougie   

A magnitude which has been corrected for the interstellar reddening.

De-reddened, p.p. of → de-redden; → magnitude.

Borz, → magnitude; vâsorxidé p.p. of vâsorxidan, → de-redden.


Fr.: dérougissement   

The process that de-reddens. The state of being de-reddened.

Verbal noun of → de-redden.


Fr.: désactiver   

To cause to be → inactive; remove the → effectiveness of (

de-; → activate.

mordé (#)

Fr.: mort   

1) Deprived of life.
2) No longer producing or functioning. → dead pixel.

M.E. deed, O.E. dead "dead;" cf. O.S. dod, Dan. død, Swed. död, Du. dood, O.H.G. tot, Ger. tot; PIE *dhou-toz-, from base *dheu- "to die."

Mordé "dead," p.p. of mordan, mir- "to die," → death.

dead pixel
  پیکسل ِ مرده   
piksel-e mordé

Fr.: pixel mort   

Of a → CCD detector, a pixel that is not sufficiently active.

dead; → pixel.


Fr.: date limite, ~ boutoir, ~ de clôture   

The time by which something must be finished or submitted; the latest time for finishing something (

Historically, during the American Civil War, the term referred to a physical line or boundary beyond which prisoners were shot; → dead; → line.

Ruzband, literally "day lock, that which blocks date," from ruz, → day, + band, → bond; cf. Ger. Stichtag, Anmeldeschluss, Einsendeschluss and Fr. date de clôture.

marg (#)

Fr.: mort   

The act of dying; the end of life.

M.E. deeth, O.E. deað (cf. O.S. doth, O.Fris. dath, Du. dood, O.H.G. tod, Ger. Tod, O.N. dauði, Dan. død, Swed. död, Goth. dauþas "death"), from *dheu- "to die" + *-thuz "-th;"

Marg "death," from Mid.Pers. marg "death;" Av. mahrka- "death," mərəxš- "ruin;" related to Mod.Pers. mordan (present stem mir-) "to die;" Mid.Pers. murdan "to die;" O.Pers. mrt- "to die," amriyta "dies," martiya- "(mortal) man" (Mod.Pers. mard "man"); Av. mərəta- "died;" cf. Skt. mar- "to die," mrti- "death," marc- "to damage, hurt, injure;" PIE base *mor-/*mr- "to die." Cognates in other IE languages: Gk. emorten "died," ambrotos "immortal;" L. morior "I die," mortuus "dead" (Fr. mourir "to die," mort "dead"); Arm. merani- "to die;" O.C.S. mrutvu "dead;" O.Ir. marb; Welsh marw "died;" O.E. morþ "murder;" Lith. mirtis.

  ۱) وازت؛ ۲) وازتیدن   
1) vâzat; 2) vâzatidan

Fr.: 1) débat; 2) débattre   

1a) A → discussion, as of a public question in an assembly, involving opposing viewpoints.
1b) A formal contest in which the affirmative and negative sides of a proposition are advocated by opposing speakers.
2) To engage in argument or discussion, as in a legislative or public assembly (

M.E. debaten, from O.Fr. debatre, literally "to fight," from → de- "down, completely," + batre "to beat," → beat.

Vâzat, from vâ-, → de-, + zat- (Baluci žat-) variant of zad-, zadan "to strike, beat", → beat.

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