An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1965 Search : ion

Fr.: discrimination   

1) An act or instance of discriminating, or of making a distinction.
2) Unfair treatment of a person, racial group, minority, etc; action based on prejudice (

Verbal noun of → discriminate.

  بهس، بحث   

Fr.: discussion   

An act or instance of discussing; → consideration or → examination by → argument, → comment, etc., especially to explore solutions; informal debate (

Verbal noun from → discuss.

  واپاشی، فروپاشی   
vâpâši, forupâši (#)

Fr.: desintégration   

The breaking up of a body into fragments. For example, that of an unstable nuclei either spontaneously or as a result of bombardment by fast-moving particles, or the breaking up of a comet.

Disintegration, verbal noun of disintegrate, from → dis- + → integration.

Vâpâši, forupâši, from vâ-, frou-de- + pâši, noun of pâšidandisperse.


Fr.: disjonction   

A → proposition of the form "A or B" (A ∨ B), where A and B are themselves propositions. A disjunction is → true when one or the other of its components (called → disjuncts) is true, and false otherwise.

dis-; → junction.

disk accretion
  فربال ِ گرده‌ای، ~ پت گرده، ~ ~ دیسک   
farbâl-e gerde-yi, ~ pat geredé, ~ ~ disk

Fr.: accrétion par disque   

An accretion process involving an → accretion disk.

disk; → accretion.

disk partition
  پرکش ِ دیسک، ~ گرده   
parkeš-e disk, ~ gerde

Fr.: partition de disque   

A logical division of a hard disk that is treated as a separate unit by operating systems and file systems.

disk; → partition.

disk population
  پرینش ِ گرده، ~ ِ دیسک   
porineš-e gerdé, ~ disk

Fr.: population disque   

Of a spiral galaxy, those stars that lie in a flattened disk and move in nearly circular orbits around its centre. They are Population I stars of all ages up to the age of the disk, but in general are younger than stars in → halo population.

disk; population, from L.L. populationem "a people, multitude," from populatio, from populare "to inhabit," from populus "people," related to plebes "the common people," cf. Gk. plethos "people, multitude, great number," from PIE base *pel- "to be full;" Mod.Pers. por "full," O.Pers. paru- "much, many," Av. pouru- "much, many," pərəna- "full," par- "to fill," Skt. puru-, Gk. polus, O.E. full "completely, full," from P.Gmc. *fullaz, O.H.G. fol, Ger. voll, Goth. full.

Like Gk., Pers. uses the concepts of "multitude, many, full" to denote "people, group, herd, flock". The following examples are all terms derived from O.Pers. paru- "much, many," Av. par- "to fill," pouru- "much, many," pərəna- "full" (Mod.Pers. por "full"): literary Pers. bâré "herd, flock," parré "a rank or file of soldiers, a circular disposition of troops," Lori, Qâyeni bor "group, tribe, herd," Torbat-Heydariyeyi, Qomi borr "heap, bundle, group," Qomi borreh "group, assemblage of people," Pashtu parrak "flock, herd," Urdu para "flock, herd," Lârestâni baila "group, tribe," Tabari balik "herd, flock." With this introduction, porineš "population," verbal noun of porinidan "to populate," infinitive of porin "populous," from por "mutitude, many, full" + -in attribution suffix.

disk truncation
  کل‌کرد ِ دیسک، ~ گرده   
kolkard-e disk, ~ gerdé

Fr.: troncature de disque   

In models of magnetized → accretion disks, the process whereby the disk is disrupted at a radius where the → magnetic pressure overcomes the → ram pressure of the accreted material. This occurs at a distance typically 3-7 stellar radii, below the → corotation radius.

disk; → truncation.

pâšeš (#)

Fr.: dispersion   

1) The resolution of white light into its component wavelengths, either by → refraction or by → diffraction. Dispersion is actually an effect in which radiations having → different wavelengths travel at different speeds in the medium. Since the → angle of refraction of each radiation vary as a function of its → wavelength, the component waves deviate from each other.
2) The rate of change of → refractive index with wavelength: dn/dλ. → Cauchy's equation shows that dispersion varies approximately as the inverse cube of the wavelength.
3) The selective → retardation of → radio waves when they propagate through a → plasma. As a result, higher → frequency waves from a → pulsar will arrive at the Earth before the lower frequencies due to the presence of → intervening → ionized gas in the → interstellar medium. → dispersion measure.
4) Statistics: The spread of values of a → variable around the → mean or → median of a → distribution.

Verbal noun of → disperse.

dispersion curve
  خم ِ پاشش   
xam-e pâšeš

Fr.: courbe de dispersion   

A graph displaying the variation of the → refractive index of a substance against the wavelength of the electromagnetic wave passing through the substance.

dispersion; → curve.

dispersion equation
  هموگش ِ پاشش   
hamugeš-e pâšeš

Fr.: équation de dispersion   

An equation representing the variation of → refractive index as a function of → wavelength; for example → Cauchy's equation and → Sellmeier's equation.

dispersion; → equation.

dispersion measure
  اندازه‌ی ِ پاشش   
andâze-ye pâšeš

Fr.: mesure de dispersion   

A parameter used in radio astronomy which describes the amount of dispersion in a radio signal due to its passage through an intervening plasma. It is proportional to the product of the interstellar electron density and the distance to the source.

dispersion; → measure.

dispersion relation
  بازانش ِ پاشش   
bâzâneš-e pâšeš

Fr.: relation de dispersion   

An equation that describes how the → angular frequency, ω, of a wave depends on its → wave number, k. For the simplest of waves, where the speed of propagation, c, is a constant, ω(k) = ck. If the → phase velocity depends on k, that is for a dispersive medium, the function ω(k) is nonlinear.

dispersion; → relation.


Fr.: disqualification   

An act or instance of disqualifying; the state of being disqualified.

disqualify; → -tion.


Fr.: rupture   

Forcible division into pieces of an object. → tidal disruption.

From L. disruptio "a breaking asunder," noun of action from p.p. stem of disrumpere "break apart, split, shatter, break to pieces," from → dis- "apart" + rumpere "to break."

Gosixt, past stem of gosixtan "to tear away, to beark off."


Fr.: dissection   

The act of dissecting.

dissect; → -tion.

  افتال، افتالش   
eftâl, eftâleš

Fr.: dissipation   

The loss of energy over time by a → dynamical system, typically due to the action of → friction or → turbulence. The lost energy is converted into heat, raising the temperature of the system. See also: → Ohmic dissipation. → viscous dissipation.

Noun form of → dissipate.


Fr.: dissociation   

General: An act or instance of dissociating; the state of being dissociated.
Chemistry: Separation of a molecule into two or more fragments (atoms, ions, radicals) by the absorption of electromagnetic radiation or the action of collisional phenomena.

From → dis- + (as)sociation, → association.

dissociation energy
  کاروژ ِ واهزش   
kâruž-e vâhazeš

Fr.: énergie de dissociation   

Energy required to dissociate a molecule. → dissociate.

dissociation; → energy.

dissociative recombination
  بازمیازش ِ واهزشی   
bâzmiyâzeš-e vâhazeši

Fr.: recombinaison dissociative   

A process where a positive molecular ion recombines with an electron, and as a result it dissociates into two neutral products. For example, AB+ + e-→ A + B, where e- is an electron, AB+ is a diatomic or polyatomic molecular ion, and A and B are the neutral fragmentation products. Dissociative recombination is the dominant recombination process in planetary ionospheres and interstellar clouds.

dissociative; → recombination.

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