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
pulsational pair-instability supernova
  ابر-نووای ِ ناپایداری ِ تپشی ِ جفت، اَبَر-نو‌اختر ~ ~ ~   
abar-novâ-ye nâpâydâri-ye tapeši-ye joft, abar-now-axtar-e ~ ~ ~

Fr.: supernova à instabilité pulsationnelle de paires   

A → supernova resulting from the → pair instability that generates several successive explosions. According to models, a first pulse ejects many solar masses of hydrogen layers as a shell. After the first explosion, the remaining core contracts and searches for a stable burning state. When the next explosion occurs a few years later, several solar masses of material are again ejected, which collide with the earlier ejecta. This collision can radiate 1050 erg of light, about a factor of ten more than an ordinary → core-collapse supernova. After each pulse, the remaining core contracts, radiates neutrinos and light, and searches again for a stable burning state. Later ejections have lower mass, but have higher energy. They quickly catch up with the first shell, where the collision dissipates most of their kinetic energy as radiation. The first SNe from → Population III stars are likely due to pulsational pair instability (Woosley et al. 2007, Nature 450, 390). See also → pair-instability supernova.

pulsational; → pair; → instability.

pycnonuclear reaction
  واژیرش ِ چگال‌هسته‌ای   
vâžireš-e cagâl-hasteyi

Fr.: réaction pycnonucléaire   

A nuclear reaction that takes place at high densities and relatively low temperatures. Pycnonuclear reactions are almost temperature independent and occur even at zero temperature. These reactions are extremely slow at densities typical for normal stars but intensify with increasing density. For example, carbon burns into heavier elements at densities over 1010 g cm-3.

Pycnonuclear, from pycno- a combining form meaning "dense, thick," from Gk. pyknos "dense, solid" + → nuclear; → reaction.

Vâžireš, → reaction; cagâl-hasteyi, from cagâl, → dense, + hasteyi, → nuclear.

quadratic equation
  هموگش ِ چاروشی   
hamugeš-e câruši

Fr.: équation quadratique   

An equation with the general form of ax2 + bx +c = 0, in which the highest power of the unknown is the second power (square).

quadratic; → equation.


Fr.: qualification   

1) A quality, accomplishment, etc., that fits a person for some function, office, or the like.
2) A circumstance or condition required by law or custom for getting, having, or exercising a right, holding an office, or the like.
3) The act of qualifying; state of being qualified (

qualify; → -tion.


Fr.: quantification   

The fact or process of quantifying.

Verbal noun of → quantify.

kuântomeš (#)

Fr.: quantification   

1) The procedure of restricting a continuous quantity to certain discrete values.
2) Physics: The procedure of deriving the quantum-mechanical laws of a system from its corresponding classical laws.

Verbal noun of → quantize.

quantum fluctuation
  افتاخیز ِ کو‌آنتومی   
oftâxiz-e kuântomi

Fr.: fluctuation quantique   

The temporary variation in a → quantum field due to the → uncertainty principle.

quantum; → fluctuation.

quantum information
  ازدایش ِ کو‌آنتومی   
azdâyeš-e kuântomi

Fr.: information quantique   

The science concerned with the transmission, storage, and processing of information using quantum mechanical systems. It exploits the notion of → quantum entanglement between systems and joins several fields of knowledge, mainly quantum physics, information, computation, and probability.

quantum; → information.

quantum of action
  کو‌آنتوم ِ ژیرش   
kuântom-e žireš

Fr.: quantum d'action   

Since → Planck's constant has the dimension of → energy × → time, its sometimes called the quantum of → action.

quantum; → action.

quantum phase transition (QPT)
  گذرش ِ فاز ِ کو‌آنتومی   
gozareš-e fâz-e kuântomi

Fr.: transition de phase quantique   

A phase transitions that occurs at zero temperature as a function of a non-thermal parameter like → pressure, → magnetic field, or → chemical composition. In contrast to ordinary → phase transitions, which are associated with passage through a critical temperature, quantum phase transitions are associated with → quantum fluctuations, a consequence of → Heisenberg's uncertainty principle. For example, see → Bose-Einstein condensation.

quantum; → phase; → transition.

quark-hadron phase transition
  گذرش ِ فاز ِ کو‌آرک-هادرون   
gozareš-e fâz-e kuârk-hâdron

Fr.: transition de phase quark-hadron   

A phase transition, predicted by cosmological models, to have occurred at approximately 10-5 seconds after the Big Bang to convert a plasma of free quarks and gluons into hadron.

quark; → hadron; → phase; → transition.

quartic equation
  هموگش ِ چارُمیک   
hamugeš-e câromik

Fr.: équation quartique   

An equation containing unknowns of the fourth power; the general form: ax4 + bx3 + cx2 + dx + e = 0.

From L. quart(us) "fourth" (→ quarter) + → -ic; → equation.

hamugeš, → equation; câromân, from cârom "fourth," from câr, cahâr "four" + -om "-th" + -ik, → -ic.

quasi-single-scattering approximation
  نزدینش ِ چونان-تک‌پراکنش   
nazdineš-e cunân-tak-parâkaneš


A model of radiative transfer that ignores forward scattering of photons; assuming forward-scattered light as un-scattered.

quasi-; → single; → scattering; → approximation.

quasiperiodic motion
  جنبش ِ چونان-دوره‌ای   
jonbeš-e cunân-dowreyi

Fr.: mouvement quasipériodique   

In a dynamical system, a form of motion that is regular but never exactly repeating. Quasiperiodic motion appears when the system contains two or more incommensurate frequencies.

quasi-; → periodic; → motion.

quintic equation
  هموگش ِ پنجمیک   
hamugeš-e panjomik

Fr.: équation quintique   

An equation containing unknowns of the fifth power.

quintic; → equation.

R association
  آهزش ِ R   
âhazeš-e R

Fr.: association R   

A → stellar association containing a number of → reflection nebulae. The stars are of low or intermediate mass and young, less than a million years old. They are still surrounded by patches of dust that reflect and absorb light from the interstellar cloud in which they formed. This type of association was first suggested by Sidney van den Bergh (1966, AJ 71, 900).

R, from → reflection; → association.

R-type ionization front
  پیشان ِ یونش ِ گونه‌ی ِ R   
pišân-e yoneš-e gune-ye R

Fr.: front d'ionisation de type R   

A spherical → ionization front of → H II regions that moves radially outward from the → exciting star at a velocity much higher than → sound speed in the surrounding cold neutral gas of uniform density (ahead of the front). R-type ionization fronts corresponds to early evolution of H II regions, and will eventually transform into → D-type ionization fronts. If the motion of the front is supersonic relative to the gas behind as well as ahead of the front, the front is referred to as weak R. The strong R front correspond to a large density increase across the front.

R referring to a rarefied gas; → type; → ionization; → front.

radial migration
  کوچ ِ شعاعی   
kuc-e šo'â'i

Fr.: migration radiale   

The process whereby a → disk star changes its → galactocentric distance. Radial migration involves → angular momentum transfer, resulting from → resonances created by transient → density waves such as → bars or → spiral arms in → galactic disks. According to → galactic dynamics models, → churning is the main cause of radial migration. Radial migration of stars plays an important role in shaping the properties of galactic disks.

radial; → migration.

radial motion
  جنبش ِ شعاعی   
jonbeš-e šo'â'i

Fr.: mouvement radial   

A motion away from or toward a central point or axis.

radial; → motion.

tâbeš (#)

Fr.: radiation, rayonnement   

The emission of any → rays, → waves, or → particles from a source; usually applied to the → emission of → electromagnetic energy.

Verbal noun of → radiate.

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