An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 120 Search : ore
Penrose theorem
  فربین ِ پنروز   
farbin-e Penrose

Fr.: théorème de Penrose   

A collapsing object whose radius is less than its Schwarzschild radius must collapse into a singularity.

Penrose process; → theorem.

perpendicular axis theorem
  فربین ِ آسه‌ها‌ی ِ پالار   
farbin-e âsehâ-ye pâlâr

Fr.: théorème des axes perpendiculaires   

The → moment of inertia of a plane object (→ lamina) about an axis perpendicular to the plane is equal to the sum of the moments of inertia about any two perpendicular axes in the plane. Thus if x and y axes are in the plane, Iz = Ix + Iy.

perpendicular; → axis; → theorem.


Fr.: phosphorescence   

A specific type of → photoluminescence that continues for an appreciable time after the stimulating process has ceased. Phosphorescence is due to the existence of metastable → excited states of the atoms and molecules from which a change to the normal state is hindered for some reason or other. The change from the → metastable metastable state to the normal one becomes possible only as a result of some additional excitation, for example the application of heat.

phosphorus; → -escence.

Poincaré recurrence theorem
  فربین ِ باز‌آمد ِ پو‌آنکاره   
farbin-e bâzâmad-e Poincaré

Fr.: théorème de récurrence de Poincaré   

In an → isolated system, any initial state will occur again in the course of the → evolution of the system over a sufficiently long but finite → time.

Poincaré sphere; → recurrence; → theorem.


Fr.: pore   

1) A small hole such as a space especially in a rock, soil, etc. → porous dust grain, → porosity.
2) A minute orifice in an animal or plant, as in the skin or a leaf.
3) Sun: A small → sunspot that does not have a → penumbra. Pores are up to about 2,500 km across and are lighter than a sunspot's → umbra. They appear and disappear at the surface of the Sun where sunspots are rarely formed, e.g. at low latitudes. Their lifetimes can be as short as 1/2 hour and as long as several days.

From L. porus "a pore," from Gk. poros "a pore," literally "passage, way," from PIE root *per- "to lead, pass over."

Lik, from Gilaki lik "hole," variants luk, luke, liuk, luxa, Tabari luk, li, Sangesari, Semnâni lu, Aftari lo.

Poynting's theorem
  فربین ِ پوینتینگ   
farbin-e Poynting

Fr.: théorème de Poynting   

The space through which electromagnetic radiation passes is filled with electric and magnetic fields at right angles to each other and to the direction of propagation of the radiation. The rate of energy transfer is given by the Poynting vector.

In honor of John Henry Poynting (1852-1914), English physicist; → theorem.

pre-cluster core
  مغزه‌ی ِ پیش-خوشه‌ای   
maqze-ye piš-xuše-yi

Fr.: cœur pré-amas   

A precursor of a small, loosely bound → star cluster (→ bound cluster) as well as an → OB association, with masses ranging from about 10 to 1000 → solar masses or more.

pre-; → cluster; → core.

pre-stellar core
  مغزه‌ی ِ پیش-ستاره‌ای   
maqze-ye piš-setâreyi

Fr.: cœur pré-stellaire   

A small, gravitationally unstable molecular → clump of typical size of less than 0.1 pc resulting from → gravitational collapse and → fragmentation of a larger → molecular cloud. It is a centrally concentrated structure which evolves into a → class 0 object, where eventually a single star or a stellar system is formed. Core masses range between 0.5 and 5 solar masses, with a mean number density of at least 104-105 cm-3, and a temperature as low as about 10 K. A pre-stellar core evolves into a → Class 0 object. Also called dense core.

pre-stellar; → core.

Pythagorean theorem
  فربین ِ پوتاگوراس، ~ فیساغورس   
farbin-e Pythagoras, ~ Fisâqures

Fr.: théorème de Pythagore   

The proposition that the → square of the → hypotenuse of a → right triangle is equal to the → sum of the squares of the other two sides: a2 + b2 = c2.

After Pythagoras (c570 BC-c495BC), Greek philosopher and mathematician; → theorem.

Pythagorean triple
  سه‌تایه‌ی ِ پوتاگوراس، ~ فیساغورس   
setâye-ye Pythagoras, ~ Fisâqures

Fr.: triplet de Phythagore   

Any group of three → integers that satisfy the relations specified by the → Pythagorean theorem. Some examples: 3, 4, and 5; 5, 12, and 13; 8, 15, 17.

Pythagorean theorem; → triple; → triplet.

reactor core
  مغزه‌ی ِ واژیرگر   
maqze-ye vâžirgar

Fr.: cœur de réacteur   

The part of a → nuclear reactor in which → nuclear fission takes place and huge quantities of heat energy are generated.

reactor; → core.

reciprocity theorem
  فربین ِ دوسویگی   
farbin-e dosuyegi

Fr.: théorème de réciprocité   

1) General: Any theorem that expresses various reciprocal relations for the behavior of some physical systems, in which input and output can be interchanged without altering the response of the system to a given excitation.
2) In classical electromagnetism, the theorem stating that the current in a detector divided by the voltage at the source remains constant when source and detector are interchanged, as long as the frequency and all the impedances are left unchanged.

Reciprocity, from L. reciproc(us) "returning the same way, alternating" + → -ity; → theorem.

Farbin, → theorem; dosuyegi, quality noun of dosuyé nuanced term of dosu "two-sided," from do, → two, + su "direction, side," from Mid.Pers. sôk "direction, side."

residue theorem
  فربین ِ مونک‌ها   
farbin-e munakhâ

Fr.: théorème des résidus   

The theorem stating that the value of the line integral of a complex function, taken along a simple closed curve encircling a finite number of isolated singularities, is given by 2πi times the sum of the residues of the function at each of the singularities.

residue; → theorem.

  بازساختن، بازگرداندن   
bâzsâxtan, bâzgardândan

Fr.: restaurer   

1) To bring back into existence, use, or the like; reestablish.
2) To bring back to a former, original, or normal condition, as a building, statue, or painting (

M.E., from O.Fr. restorer, from L. restaurare "repair, rebuild, renew," from → re- "back, again" + -staurare, from PIE root *sta- "to stand, set down, make or be firm," → state.

Bâzsâxtan, from bâz- "back, again," → re-, + sâxtan "to build, make, fashion; to adapt, adjust, be fit" (from Mid.Pers. sâxtan, sâz-, Manichean Parthian s'c'dn "to prepare, to form;" Av. sak- "to understand, to mark," sâcaya- (causative) "to teach").
Bâzgardândan, from bâz-+ gardândan "to turn (around)," accusative of gardidan, gaštan "to change, to turn, → revolve."

restored image
  وینه‌ی ِ بازساخته، تصویر ِ ~   
vine-ye bâzsâxté, tasvir-e ~

Fr.: image restaurée   

An image that has been upgraded by a process of → image restoration.

Restored, p;p. of restore, → restoration; → image.

Tasvir, → image; bâzsâxté, p.p. of bâzsâxtan, → restoration.

Rolle's theorem
  فربین ِ رول   
farbin-e Rolle

Fr.: théorème de Rolle   

If a function f(x) is → continuous on an interval [a,b] and is → differentiable at all points within this interval, and vanishes at the end points x = a and x = b, that is f(a) = f(b) = 0, then inside [a,b] there exists at least one point x = c, a < c < b, at which the derivative f'(x) vanishes.

Named after Michel Rolle (1652-1719), a French mathematician; → theorem.

Russell-Vogt theorem
  فربین ِ راسل-فوکت   
farbin-e Russell-Vogt

Fr.: théorème de Russell-Vogt   

A uniqueness theorem involving the equations of state of stellar structure. → Vogt-Russell theorem.

Named after the German astronomer Heinrich Vogt (1890-1968) and the American astronomer Henry Norris Russell (1877-1957); → theorem.

sampling theorem
  فربین ِ نمونان‌گیری   
farbin-e nemunân-giri

Fr.: théorème d'échantillonnage   

Same as → Nyquist-Shannon sampling theorem.

sampling; → theorem.

second core
  مغزه‌ی ِ دوم   
maqze-ye dovom

Fr.: deuxième cœur   

A hydrostatic object predicted to result from the → second collapse of a → molecular cloud in an early stage of star formation.

second; → core.

Shannon's sampling theorem
  فربین ِ نمونان‌گیری ِ شانون   
farbin-e nemunân-giri-ye Shannon

Fr.: théorème d'échantillonnage de Shannon   

Same as → sampling theorem.

Shannon entropy; → sampling; → theorem.

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