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
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.


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.


Fr.: participation   

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

Verbal noun of → participate.

particular solution
  لویش ِ پارولی   
luyeš-e pâruli

Fr.: solution particulière   

Of partial differential equations, the solution which can be obtained from the general solution by particular choice of the arbitrary functions. → general solution; → singular solution.

particular; → solution.

  ۱) پرکه؛ ۲) پرکش؛ ۳) پرکیدن   
1) parke; 2) parkeš 3) parkidan

Fr.: 1, 2) parition, cloison, division; 3) cloisonner, diviser   

1a) A division into or distribution in portions or shares.
1b) A separation; something that separates or divides; a part, division, or section.
2a) The act or process of dividing something into parts. The state of being so divided.
2b) Math.: → integer partition; → set partition.
2c) Computers: → disk partition.
3) To divide into parts or portions. To divide or separate by a partition.

M.E., from O.Fr. particion, from L. partition- "division, partition, distribution," from p.p. stem of partire "to part, divide," from PIE root *per- "to grant, allot," related to → part and akin to pake, as below.

Parke, from Kermâni parke "piece, part, fragmant," related to pâr "→ part;" parkidan, infinitive from parke; parkeš, verbal noun of parkidan.

partition function
  کرپای ِ پرکش   
karâ-ye parkeš

Fr.: fonction de partition   

See → integer partition.

partition; → function.

partition ratio
  وابر ِ پرکش   
vâbar-e parkeš

Fr.: rapport de partition   

The ratio of the → concentration of a → solute in a single definite form in the stationary phase to its concentration in the same form in the other phase at equilibrium.

partition; → ratio.


Fr.: partition   

A chemical separation process whereby a solute is distributed between two phases.

partition; → -ing.



The act or fact of being partitioned.

partition; → -ment.

parts per million (ppm)
  پار در میلیون   
pâr dar milion

Fr.: partie par million   

A fraction of a whole number in units of 1/1000,000. It is usually used to describe chemical concentrations, very small amounts of pollutants in air, water, body fluids, and uncertainty. For example 30 ppm is 3 x 10-5 or 0.003%.

part; → per; → million.

Pauli exclusion principle
  پروز ِ سکلان ِ پاؤلی   
parvaz-e sokolân-e Pauli

Fr.: principe d'exclusion de Pauli   

A quantum mechanical principle according to which no two identical → fermions can share the same → quantum state. Also known as → exclusion principle.

In honor of Wolfgang Pauli (1900-1958), Austrian theoretical physicist, who formulated the principle in 1925; → exclusion; → principle.

pebble accretion
  فربال ِ ریگ   
farbâl-e rig

Fr.: accrétion de galets   

A planet formation concept that concerns the → accretion of small objects of negligible gravitational mass (ranging from centimeters up to meters in diameter) onto large, gravitating bodies: → planetesimals, → protoplanets, or → planets. In a more narrow sense, pebble accretion is an accretion process where (gas) drag and gravity play major roles. Simply put, this means that the pebble has to be aerodynamically small and the planet to be gravitationally large (C. W. Ormel, in Formation, Evolution, and Dynamics of Young Solar Systems, p. 197, eds. M. Pessah, O. Gressel, Springer, 2017).

pebble; → accretion.

peculiar motion
  جنبش ِ اَفد   
jonbeš-e afd

Fr.: mouvement particulier   

1) The true motion of a star with respect to the Local Standard of Rest. → proper motion.
2) The motion of a cosmological object other than the apparent recession caused by the expansion of the Universe.

peculiar; → motion.


Fr.: péjoration   

1) Depreciation; a lessening in worth, quality, etc.
2) Semantic change in a word to a lower, less approved, or less respectable meaning.

Verbal noun of → pejorate.


Fr.: perception   

The process of recognizing or identifying something. Usually employed of sense perception, when the thing which we recognize or identify is the object affecting a sense organ.

Verbal noun of → perceive.

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