An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1234
sanjidâr (#)

Fr.: critère   

A standard or rule that can serve as basis for a judgment or decision.

From Gk. kriterion "means for judging, standard," from krites "judge," from krinein "to separate, distinguish, judge." L. cribrum "sieve" *krei- "to sieve, discriminate, distinguish."

Sanjidâr verbal noun from sanjid- past tense stem of sanjidan "to compare; to measure" (Mid.Pers. sanjidan "to weigh," from present tense stem sanj-, Av. θanj- "to draw, pull;" Proto-Iranian *θanj-) + suffix -âr.

  پرژنکار، پرژنگر   
paržankâr, paržangar

Fr.: critique   

A person who judges, evaluates, or criticizes.

M.E., from M.Fr. critique, from L. criticus "a judge, literary critic," → critique.

Paržangar, from paržan present stem of paržanidan, "criticize", → critique, + -kâr, -gar suffixes of agent nouns, → -or.


Fr.: critique   

1) Of or pertaining to → critics or → criticism.
2) Of, relating to, or being a state or level at which a significant change takes place (

critic; → -al.

critical angle
  زاویه‌ی ِ پرژنی   
zâviyeh-ye paržani

Fr.: angle critique   

Angle of incidence of light proceeding from a denser medium toward a thinner, at which grazing refraction occurs (angle of refraction 90°).

critical; → angle.

critical Bonnor-Ebert mass
  جرم ِ پرژنی ِ بونور-ابرت   
jerm-e paržani-ye Bonnor-Ebert

Fr.: masse critique de Bonnor-Ebert   

The upper value of mass that a → Bonnor-Ebert sphere must have in order that → hydrodynamic equilibrium be maintained. This → critical mass is given by: Mcrit = 1.18 (a4/G3/2)Pext-1/2, where a = (kT/m)1/2 is the isothermal → sound speed inside the sphere, G is the → gravitational constant, and Pext the pressure of the external medium (see, e.g., F. H. Shu, 1977, ApJ 214, 488).

critical; → Bonnor-Ebert mass.

critical density
  چگالی ِ پرژنی   
cagâli-ye paržani

Fr.: densité critique   

1) Cosmology: The average density of matter in the Universe that would be needed to eventually halt the → cosmic expansion. In a spatially → flat Universe, the critical density is expressed by ρc = (3c2/8πG)Ht2, where c is the → speed of light, G is the → gravitational constant, and Ht the → Hubble parameter. The critical density is currently 9.3 × 10-30g cm-3, about 6 hydrogen atoms per cubic meter (for H0 = 70 km s-1 Mpc-1).
2) In → gravitational lensing, the minimum density that would be needed by an intervening object to bend light rays. It is expressed by: Σ = (c2/4πG)(dos/doldls), where c is the speed of light, G is the gravitational constant, dos, dol, and dls represent angular diameter distances between the observer and the source, the observer and the lens, and the lens and the source respectively. It has units of mass per unit solid angle.
3) Radiative processes: The density at which the collisional → de-excitation rate equals the → radiative transition rate. The critical density for level j is given by: nc = Σi < j Aji = Σi ≠ j qji, where Aji is the → Einstein coefficient of → spontaneous emission and qji is the rate for collisional de-excitation of → energy level j, summed over all possible processes. This expression often simplifies to the ratio of two numbers, since in many cases there is a single important path for emission and a dominant collisional de-excitation process. In the low density limit the → emissivity is proportional to the product Ne (electron density) x Ni (ion density), whereas for densities exceeding the critical density, the emissivity is proportional to Ni. Thus, line emission in a nebula occurs most efficiently near the critical density.

critical; → density.

critical mass
  جرم ِ پرژنی   
jerm-e paržani

Fr.: masse critique   

Of a fissile material (235U or 239Pu), the minimum mass needed for a sustained nuclear chain reaction, as in an atomic bomb.

critical; → mass.

critical metallicity
  فلزیگی ِ پرژنی   
felezigi-ye paržani

Fr.: métallicité critique   

The → metallicity of a → star-forming  → molecular cloud when → cooling → rates by → metals dominate the → gravitational  → heating during → protostellar collapse. The minimum → Jeans mass achieved by gravitational → fragmentation depends on the presence/absence of → coolants in the cloud. Since cooling rate in metal lines is more efficient than in primordial molecular lines (H2 and HD), metals favor fragmentation in gas and formation of → low-mass stars.

critical; → metallicity.

critical opalescence
  اپالستی ِ پرژنی   
opâlesti-ye paržani

Fr.: opalescence critique   

The strong → scattering that occurs in a fluid near the → critical point. Large density fluctuations bring about inhomogeneities of all sizes. This results in the scattering of light at all wavelengths giving a milky appearance to the fluid.

critical; → opalescence.

critical velocity
  تندای ِ پرژنی   
tondâ-ye paržani

Fr.: vitesse critique   

1) Velocity of → fluid through a pipe at which the motion changes from → laminar to → turbulent flow.
2) Same as → break-up velocity.

critical; → velocity.

  ۱)، ۲) پرژنش، پرژنکاری، پرژنگری؛ ۳) پرژن   
1), 2) paržaneš, paržankâri, paržangari; 3) paržan

Fr.: critique   

1) The act of passing judgment as to the merits of anything.
2) The act or art of analyzing and evaluating or judging the quality of a literary or artistic work, musical performance, art exhibit, dramatic production, etc.
3) A critical comment, article, or essay; → critique (

critic; → -ism.


Fr.: critiquer, faire la critique de   

To judge or discuss the merits and faults of.

critic; → -ize.


Fr.: critique   

1) An article or essay criticizing a literary or other work; detailed evaluation; review.
2) A criticism or critical comment on some problem, subject, etc.
3) The art or practice of criticism (

From M.Fr. Fr. critique, from L. criticus "a judge, literary critic," from Gk. kritikos "able to make judgments," from krinein "to sift, separate, decide;" cognate with Pers. qarbâl "sieve," → sieve of Eratosthenes. from PIE base *krei- "to sift, distinguish."

Paržan, from Tâti Karingâni puržen, Zazaki pirožin, Tabari parjan "sieve," related to parvizan "sieve" (Laki vežonen "to sift"); ultimately from Proto-Ir. *pari-uaicana-, from the base *uaic- "to separate, sift, select, sort out;" Av. vaēc- "to select, sort out, sift;" Mod.Pers. bixtan, biz- "to sift."

  چلیپا، خاج   
calipâ (#), xâj (#)

Fr.: croix   

(n.) 1a) The Southern Cross, → Crux. 1b) A figure or pattern formed by the intersection of two lines.
(adj.) 2a) Involving interchange; reciprocal. 2b) Lying or passing crosswise; intersecting.

M.E. cros, from O.E., probably from Old Norse kross, from O.Ir. cros, from L. crux "stake, cross."

Calipâ, loanword from Aramaic. Xâj loanword from Arm.

cross correlation
  هم‌باز‌آنش ِ چلیپایی، ~ خاجی   
hamvbâzâneš-e calipâyi, ~ xâji

Fr.: corrélation croisée   

In radio astronomy, the process performed by a → cross correlator or the result of the process.

cross; → correlation.

cross correlator
  هم‌باز‌آن‌گر ِ چلیپایی، ~ خاجی   
hambâzângar-e calipâyi, ~ xâji

Fr.: corrélateur   

In radio interferometry, a device that multiplies together the signals received by each pair of antennas in an array and performs several operations on the signal (filtering out the noise added to the signal by the receiver electronics, correcting for the Doppler shift and geometric delay due to the position and motion of the antennas). The correlated signal, corresponding to the spatial frequency given by the distance between the two antennas, is then combined with the other spatial frequency to reconstruct the map of the source.

cross; → correlator.

cross disperser
  پاشنده‌ی ِ چلیپایی، ~ خاجی   
pâšande-ye calipâyi, ~ xâji


A device producing cross dispersion.

cross; → disperser.

cross dispersion
  پاشش چلیپایی، ~ خاجی   
pâšeš-e calipâyi, ~ xâji

Fr.: dispersion croisée   

Dispersion of a light beam by using two dispersing elements (grating, grism), one for separating spectral orders, the other for resolving spectral features within an order.

cross; → dispersion.

cross identification
  ایدانش ِ چلیپایی   
idâneš-e calipâyi

Fr.: identification croisée   

The identification of an object in a data base or catalog and matching it with the same object identified in another catalog.

cross; → identification.

cross product
  فر‌آورد ِ برداری   
farâvard-e bordâri

Fr.: produit vectoriel   

Same as → vector product.

cross; → product.

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