An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 495
  نور-زمان، زمان ِ نوری   
nur-zamân, zamân-e nuri (#)

Fr.: temps-lumière   

The time it takes for light, travelling at about 300 000 km per second, to travel a certain distance.

light; → time.

light-travel distance
  اپست ِ سفر ِ نور   
apest-e safar-e nur

Fr.: distance du voyage de la lumière   

The distance traversed by a photon between the time it is emitted and the time it reaches the observer. It is also referred to as the → look-back time.

light; → travel; → distance.

  نور-سال، سال ِ نوری   
nur-sâl (#), sâl-e nuri (#)

Fr.: année-lumière   

The distance that light travels in one year at about 300,000 km per second, i.e. 9.5 x 1012 km. It is equal to about 63,000 → astronomical units. See also → parsec.

light; → year.


Fr.: faisceau de fibres optiques; guide d'ondes optique   

A bundle of optical fibers arranged randomly for the purpose of transmitting energy, not an image.

light; → guide.


Fr.: genre lumière   

Of, pertaining to, or describing an → event on the → light cone.

light; → -like.

lightlike interval
  اندروار ِ نورسان   
andarvâr-e nursân

Fr.: intervalle genre lumière   

The space-time interval between two events if it is zero, i.e. ds2 = 0.

lightlike; → interval.

âzaraxš (#)

Fr.: foudre   

A → flash of light produced by an → electric discharge in response to the buildup of an → electric potential between → cloud and → Earth's surface, or between different portions of the same cloud.

Lightning, pr.p. of lightnen "make bright," extended form of O.E. lihting, from leht, → light.

Âzaraxš, from âzar "fire," variants âtaš, taš (Mid.Pers. âtaxš, âtur "fire;" Av. ātar-, āθr- "fire," singular nominative ātarš-; O.Pers. ātar- "fire;" Av. āθaurvan- "fire priest;" Skt. átharvan- "fire priest;" cf. L. ater "black" ("blackened by fire"); Arm. airem "burns;" Serb. vatra "fire;" PIE base *āter- "fire") + raxš "lightning, reflection of light," raxšidan "to shine, flash," variant deraxš, deraxšidan "to shine, radiate" (O.Pers. raucah-, Av. raocah- "light" (cf. Skt. roka- "brightness, light," Gk. leukos "white, clear," L. lux "light" (also lumen, luna), E. light, Ger. Licht, Fr. lumière; PIE base *leuk- "light, brightness"); cognate with Mod.Pers. words ruz "day," rowšan "bright, clear," foruq "light," and afruxtan "to light, kindle").


Fr.: vraisemblance   

1) The state of being likely or probable; a probability or chance of something.
2) In technical language likelihood is not synonymous for probability. Same as → likelihood function.

From → likely + -hood a suffix denoting state, condition, character, nature, etc., from M.E. -hode, -hod, O.E. -hād (cf. Ger. -heit).

Šodvâri, noun of šodvâr, → likely.

likelihood function
  کریای ِ شدواری   
karyâ-ye šodvâri

Fr.: fonction de vraisemblance   

A function that allows one to estimate unknown parameters based on known outcomes. Opposed to → probability, which allows one to predict unknown outcomes based on known parameters. More specifically, a probability refers to the occurrence of future events, while a likelihood refers to past events with known outcomes.

likelihood; → function.


Fr.: vraisemblable   

Probably or apparently destined; having a high probability of occurring or being true.

Perhaps from O.N. likligr "likely," from likr "like" (adj.).

Šodvâr, from šod past stem of šodan "to become, to be, to be doing, to go, to pass" + -vâr a suffix with several meanings "resembling, like, in the manner of; having, endowed with." The first element from Mid.Pers. šudan, šaw- "to go;" Av. šiyav-, š(ii)auu- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" cf. Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Gk. kinein "to move;" Goth. haitan "call, be called;" O.E. hatan "command, call;" PIE base *kei- "to move to and fro."

labé (#)

Fr.: bord   

1) The outer edge or border of the apparent disk of a celestial body. → limb brightening, → limb darkening.
2) The raised edge of the mater of a → planispheric astrolabe, bearing a scale divided into 360°. The limb is the reference against which the rete is rotated in the computation process so that the planispheric astrolabe will simulate the sky's appearance on a given day at a specific hour. Vice versa, the limb can be configured from the observation of the altitude of an celestial body on the horizon. In that case, the limb will indicate an angle that, thanks to the hour scale on the back, can be converted into the hour of day or night (online museo galileo, VirtualMuseum).

From L. limbus "border, hem, fringe, edge," cognate with Skt. lambate "hangs down."

Labé "limb, edge," from lab "lip;" Mid.Pers. lap; cognate with L. labium, E. lip; Ger. Lefze.

limb brightening
  روشنش ِ لبه   
rowšaneš-e labé

Fr.: embrillancement centre-bord   

An observed increase in the intensity of radio, extreme ultraviolet, or X-radiation from the Sun from its center to its limb.

limb; → brightening.

limb darkening
  تاریکش ِ لبه   
târikeš-e labé

Fr.: assombrissement centre-bord   

An apparent decrease in brightness of the Sun near its edge as compared to its brightness toward the center. Limb darkening is readily apparent in photographs of the Sun. The reason is that when we look toward the disk's center we look into deeper and hence hotter layers along the line of sight. Toward the limb, we get radiation from higher and hence cooler and less bright layers of the → photosphere. Limb darkening has been detected in the case of several other stars. A similar phenomenon occurs in → eclipsing binaries where the effect of limb darkening on one or both components manifests itself in the shape of the system's → light curve.

limb; → darkening.

âhak (#)

Fr.: chaux   

A white or grayish-white substance obtained by burning → limestone, used in mortars, plasters, cements, and in the manufacture of steel, paper, glass, and various chemicals of calcium.

M.E., O.E. lim; akin to Du. lijm, Ger. Leim, O.N. lim "glue;" L. limus "slime."

Âhak, probably a variant of xâk, → soil.

  سنگ ِ آهک   
sang-e âhak (#)

Fr.: castine, calcaire    

A → sedimentary rock composed principally of calcium carbonate. Limestone is usually formed from shells of once-living organisms or other organic processes, but may also form by inorganic precipitation.

lime; → stone.

hadd (#)

Fr.: limite   

1) General: The final, utmost, or furthest → boundary or → point as to extent, amount, continuance, procedure, etc.
2a) Math.: Of a → sequence, a → number which is approached ever more closely, but never reached, by the successive terms of a convergent infinite sequence.
2b) Of a → variable, a constant C which has the property with respect to some variable V that, as the variable approaches C in value (according to some formula), the numerical difference (C - V) between the constant and the variable diminishes toward 0 but is always greater than 0.

From O.Fr. limite "a boundary," from L. limitem (nom. limes) "a boundary, embankment between fields, border," related to limen "threshold."

Loan from Ar. Hadd "limit, term."


Fr.: limité   

Confined within limits; restricted or circumscribed.

Adj. of → limit.

limiting magnitude
  برز ِ حد   
borz-e hadd

Fr.: magnitude limite   

The faintest magnitude reachable by an instrument.

limit; → magnitude.

limonit (#)

Fr.: limonite   

A widely occurring ore of yellowish-brown to black color that consists of amorphous oxides of iron.

Gk. leimon "meadow" in reference to its occurrence as "bog ore" in meadows and marshes + → -ite.

Lindblad resonance
  باز‌آوایی ِ لیندبلاد   
bâzâvâyi-ye Lindblad

Fr.: résonance de Lindblad   

A kinematic resonance hypothesized to explain the existence of galactic → spiral arms. It occurs when the frequency at which a star encounters the spiral → density wave is a multiple of its → epicyclic frequency. Orbital resonances occur at the location in the disk where Ωp = Ω ± κ/m, where Ωp is → pattern speed, κ → epicyclic frequency, and m an integer representing the number of spiral arms. The minus sign corresponds to the inner Lindblad resonance (ILR) and the plus sign to the outer Lindblad resonance (OLR). The corotation resonance corresponds to Ωp = Ω. In general, the Lindblad resonances are defined for two spiral arms (m = 2), and low order. There are other less important resonances corresponding to higher m values. These resonances tend to increase the object's orbital eccentricity and to cause its longitude of periapse to line up in phase with the perturbing force. Lindblad resonances drive spiral density waves both in galaxies (where stars are subject to forcing by the spiral arms themselves) and in Saturn's rings (where ring particles are subject to forcing by Saturn's moons).

After the originator of the model, Bertil Lindblad (1895-1965), a Swedish astronomer, who made important contributions to the study of the rotation of the Galaxy; → resonance.

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