An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 3079 Search : on
oxidation
  ا ُکسایش   
oksâyeš (#)

Fr.: oxydation   

The combination of → oxygen with a substance, or the removal of → hydrogen from it.

Verbal noun of → oxidize.

oxidation number
  شمار ِ اکسایش   
šomâr-e oksâyeš

Fr.: nombre d'oxydation   

The total number of electrons that an atom either gains or loses in order to form a chemical bond with another atom. In other words, the charge that atom would have if the compound was composed of ions. The oxidation number of an atom is zero in a neutral substance that contains atoms of only one element. Same as → oxidation state.

oxidation; → number.

oxidation state
  استات ِ اکسایش   
estât-e oksâyeš

Fr.: état d'oxydation   

Same as → oxidation number.

oxidation; → state.

ozone
  ازون   
ozon (#)

Fr.: ozone   

A form of oxygen, O3, in which the molecule is made of three atoms instead of the usual two.

From Ger. Ozon, coined in 1840 by Ger. chemist Christian Friedrich Schönbein (1799-1868) from Gk. ozon, neute pr.p. of ozein "to smell." So called for its peculiar odor.

ozone hole
  سوراخِ اُزون   
surâx-e ozon (#)

Fr.: trou d'ozone   

Not really a "hole," but a region of exceptionally depleted ozone in the stratosphere over the Antarctic that happens at the beginning of Southern Hemisphere spring (August-October). It was first noticed in the 1970s by a research group from the British Antarctic Survey.

ozone; → hole.

ozone layer
  لایه‌یِ اُزون   
lâye-ye ozon (#)

Fr.: couche d'ozone   

An atmospheric layer that contains a high proportion of oxygen that exists as ozone. It acts as a filtering mechanism against incoming ultraviolet radiation. It is located between the troposphere and the stratosphere, around 15 to 20 kilometers above the Earth's surface.

ozone; → layer.

ozone shield
  سپرِ اُزون   
separ-e ozon (#)

Fr.: bouclier d'ozone   

The ozone layer within the stratosphere that filters out potentially lethal intensities of ultraviolet radiation from the Sun.

ozone; shield, from O.E. scield, scild, related to sciell "seashell, eggshell," from P.Gmc. *skeldus (cf. Du. schild, Ger. Schild, Goth. skildus); PIE base *(s)kel- "to cut."

Separ "shield," from Mid.Pers. spar "shield;" cf. Skt. phalaka- "board, lath, leaf, shield," phálati "(he) splits;" Gk. aspalon "skin, hide," spolas "flayed skin," sphalassein "to cleave, to disrupt;" O.H.G. spaltan "to split;" Goth. spilda "board;" PIE base *(s)p(h)el- "to split, to break off;" → ozone.

packing fraction
  برخه‌ی ِ انباشتگی   
barxe-ye anbâštegi (#)

Fr.: coefficient de tassement   

The difference between the isotopic mass of a nuclide and its mass number divided by its mass number. The packing fraction is a measure of the stability of the nucleus.

Packing, from the verb pack "to put together in a pack," from the noun pack, from M.E. pak, packe, from M.D. pac or perhaps M.L.G. pak; → fraction.

Barxé, → fraction; anbâštegi quality noun of anbâštan, anbârdan "to fill, to replete;" Mid.Pers. hambāridan "to fill;" from Proto-Iranian *ham-par-, from prefix ham- + par- "to fill;" cf. Av. par- "to fill," parav-, pauru-, pouru- "full, much, many;" O.Pers. paru- "much, many;" Mid.Pers. purr "full;" Mod.Pers. por "full, much, very;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full.

pair annihilation
  نابودی ِ جفت   
nâbudi-ye joft

Fr.: annihilation de paire   

Mutual destruction of a particle and its antiparticle, such as an electron-positron pair, when they collide. The total energy of the two particles is converted into energy as gamma rays. It is the inverse process to → pair production.

pair; → annihilation

pair production
  فر‌آورش ِ جفت   
farâvareš-e joft

Fr.: production de paires   

The creation of an → elementary particle and its → antiparticle from a → boson. For example, the formation of an → electron and a → positron in the interaction of high-energy → gamma ray photons, having at least 1.02 Mev, with an → atomic nucleus (γ → e- + e+). The → rest masses of the electron and positron being 0.51 MeV each, the excess energy will be carried away by these two particles. Pair production is the inverse process to → pair annihilation.

pair; → production

paleontology
  پارین‌شناسی   
pârin-šenâsi (#)

Fr.: paléontologie   

The study of ancient life through → fossils.

From Fr. paléontologie, from paléo-, → paleo-, + onto-, from Gk. ont- "being," pr.p. of einai "to be," + → -logy.

Pârin-šenâsi, from pârin-, → paleo- + šenâsi, → -logy.

parallactic motion
  جنبش ِ دیدگشتی   
jonbeš-e didgašti

Fr.: mouvement parallactique   

The proper motion of a star due to the effect of the Sun's motion relative to the → local standard of rest.

parallactic; → motion.

parametric equation
  هموگش ِ پارامونی   
hamugeš-e pârâmuni

Fr.: équation paramétrique   

Any of a set of equations that defines the coordinates of the dependent variables of a curve or surface in terms of one or more independent variables or parameters.

parametric; → equation.

parhelion
  پراهور   
parâhur

Fr.: parhélie   

An atmospheric optical phenomenon, seen as a bright spot sometimes appearing at either side of the → Sun, often on a luminous ring or → halo and at the same angular elevation as the Sun. Parhelia are caused by the → refraction and → reflection of → sunlight by → ice crystals suspended in the Earth's → atmosphere. Also called mock Sun or sundog.

From Gk. parhelion "a mock Sun," from → para- "beside" + helios "sun," → helio-.

Parâhur, from parâ-, → para-, + hur "sun," → helio-.

parity conservation
  پتایش ِ همالی   
patâyeš-e hamâli

Fr.: conservation de parité   

In quantum mechanics, the condition of parity in strong and electrodynamic interactions, where it remains constant and does not change with time. In other words, parity conservation implies that Nature is symmetrical and makes no distinction between right- and left-handed rotations or between opposite sides of a subatomic particle. Thus, for example, two similar radioactive particles spinning in opposite directions about a vertical axis should emit their decay products with the same intensity upward and downward. Same as → parity symmetry.

parity; → conservation.

parity violation
  اِناهش ِ همالی   
enâheš-e hamâli

Fr.: violation de la parité   

In quantum mechanics, the condition of → parity in the → weak interaction. For example, the emitted → beta particles in → radioactive decay of → cobalt-60 nuclei are not equally distributed between the two poles of cobalt-60. More beta particles emerge from one pole than the other, and it would be possible to distinguish the mirror image nuclei from their counterparts.

parity; → violation.

Parkes Selected Region (PSR)
  ناحیه‌ی ِ گزیده‌ی ِ پارکس   
nâhiye-ye gozide-ye Parkes

Fr.: Région sélectionnée de Parkes   

A catalog of 397 radio sources between declinations +20° and +27° which were compiled from a finding survey made at 635 MHz with the 64m radio telescope at the Australian National Radio Astronomy Observatory, Parkes, N.S.W. and published in 1968. Originally abbreviated PSR, this catalog, which is also called PKS, replaces and improves on four earlier lists (1964 to 1966).

Parkes, proper noun; selected, p.p. of → select; → region.

partial differential equation
  هموگش ِ دگرسانه‌ای با واخنه‌ی ِ پاری   
hamugeš-e degarsâne-yi bâ vâxane-ye pâri

Fr.: équation différentielle aux dérivées partielles   

A type of differential equation involving an unknown function (or functions) of several independent variables and its (or their) partial derivatives with respect to those variables.

partial; → differential; → equation.

partial ionization zone
  زنار ِ یونش ِ پاری   
zonâr-e yoneš-e pâri

Fr.: zone d'ionisation partielle   

One of several zones of the stellar interior where increased → opacity can provide the → kappa mechanism to drive → pulsations. See also → Kramers' law. In these zones where the gases are partially ionized, part of the energy released during a layer's compression can be used for further ionization, rather than raising the temperature of the gas. Partial ionization zones modulate the flow of energy through the layers of the star and are the direct cause of → stellar pulsation. The partial ionization zones were first identified by the Russian astronomer Sergei A. Zhevakin (1916-2001) in the 1950s. In most stars there are two main ionization zones. The hydrogen partial ionization zone where both the ionization of neutral hydrogen (H ↔ H+ + e-) and the first ionization of helium (He ↔ He+ + e-) occurs in layers with a characteristic temperature of 1.5 x 104 K. The second, deeper zone is called the He+ partial ionization zone, and involves the second ionization of helium (He+↔ He++ + e-), which occurs deeper at a characteristic temperature of 4 x 104 K. The location of these ionization zones within the star determines its pulsational properties. In fact if the → effective temperature of the star is ≥ 7500 K, the pulsation is not active, because the ionization zones will be located very near to the surface. In this region the density is quite low and there is not enough mass available to drive the oscillations. This explains the blue (hot) edge of the instability strip on the → H-R diagram. Otherwise if a star's surface temperature is too low, ≤ 5500 K, the onset of efficient convection in its outer layers may dampen the oscillations. The red (cool) edge of the instability strip is believed to be the result of the damping effect of convection. He+ ionization is the driving agent in → Cepheids. See also → gamma mechanism.

partial; → ionization; → zone.

participation
  پارگرت   
pârgert

Fr.: participation   

An act or instance of participating. The fact of taking part.

Verbal noun of → participate.

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