An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1026
perturbation method
  روش ِ پرتورش   
raveš-e partureš

Fr.: méthode de perturbation   

Approximate method of solving a difficult problem if the equations to be solved depart only slightly from those of a problem already solved.

perturbation; → method.

perturber body
  جسم ِ پرتورنده   
jesm-e parturandé

Fr.: corps perturbateur   

A celestial body that causes a perturbation in the orbit of another body.

Agent noun of → perturb; → body.

petâ- (#)

Fr.: péta-   

A prefix denoting 1015.

Of unknown origin.

sang- (#)

Fr.: petro-   

A combining form meaning "rock," "stone." Also, petri-, and petr- when before a vowel.

From Gk. petro-, combining form of petra "rock."

Sang "rock," → stone.

naft (#)

Fr.: pétrole   

Natural mixture of liquid hydrocarbons and other organic compounds that include crude oil, refined products obtained from the processing of crude oil, and natural gas liquids.

M.L. petroleum literally "rock oil," from L. petra "rock," from Gk. → petro-, + oleum "oil."

Naft, from Mid.Pers. npt "moist, damp; naphtha," nmb "moisture," from which derives Mod.Pers. nam "humidity, moisture;" Av. napta- "moist," nabah- "cloud; sky;" cf. Skt. nábhas- "moisture, cloud, mist;" PIE base *nebh- "cloud, vapor, fog, moist, sky" (Gk. nephos "cloud, mass of clouds," nephele "cloud;" L. nebula "mist," nimbus "rainstorm, rain cloud;" O.H.G. nebul; Ger. Nebel "fog;" O.E. nifol "dark"). The link between "water, moisture" and "naphta" is suggested to be the natural gas or oil seepages surfacing through water. In fact many of the Zoroastrian fire-temples were located in areas which contained large petroleum leakages, such as those in Khuzestân and at Surakhany near Baku.

sangšenâsi (#)

Fr.: pétrologie   

The branch of → geology that deals with → rocks: their classification, composition, structure, occurrence, and conditions of origin.

petro-; → -logy


Fr.: peVatron   

An astrophysical source which accelerates → cosmic rays up to energies of several petaelectronvolts. For example, in the → Galactic center, cosmic ray → protons reach such energies. The source of such particles is a matter of research (→ HESS collaboration, 2016, Nature 531, 476).

PeVatron, from PeV (→ peta- + → electronvolt); + euphonic affix -a-; + → -tron.

Pfund series
  سری ِ پفوند   
seri-ye Pfund

Fr.: série de Pfund   

A series of lines in the infrared spectrum of atomic hydrogen whose representing transitions between the fifth energy level and higher levels.

After August Herman Pfund (1879-1949), an American physicist and spectroscopist; → series.

PG 1159 star
PG 1159

Fr.: PG 1159   

A member of the class of stars in transition between → post-AGB and → white dwarf stars, with temperatures as high as 200,000 K, mean mass about 0.6 Msun, and log g = 5.5-8. PG 1159 stars have no hydrogen or He I lines in their spectra, but do show weak He II lines and stronger lines of ionized carbon and oxygen. These stars are thought to be the exposed inner core of a star that has exploded as a → planetary nebula and is on its way to become a white dwarf. Also called → pre-degenerate star

Named after their prototype PG 1159-035, from the Palomar-Green Catalog of Ultraviolet Excess Stellar Objects (Green et al. 1986, ApJS 61, 305); → star.

  پ-هاش، پی-اچ   
p-hâš, pi-ec

Fr.: potentiel hydrogène   

A → logarithmic measure of → hydrogen ion concentration, originally defined pH = log10 (1/[H+]), where [H+] is the concentration of hydrogen ions in → moles per liter of solution. The hydrogen ion concentration in pure water around room temperature is about 1.0 × 10-7 moles. Therefore, a pH of 7 is considered "neutral," because the concentration of hydrogen ions is exactly equal to the concentration of → hydroxide (OH-) ions produced by → dissociation of the → water. Increasing the concentration of hydrogen ions above 1.0 × 10-7 moles produces a solution with a pH of less than 7, and the solution is considered → acidic. Decreasing the concentration below 1.0 × 10-7 moles produces a solution with a pH above 7, and the solution is considered → alkaline or → basic. The neutral pH is different for each → solvent. For example, the concentration of hydrogen ions in pure ethanol is about 1.58 × 10-10 moles, so ethanol is neutral at pH 9.8. A solution with a pH of 8 would be considered acidic in ethanol, but basic in water.

From Ger. PH, introduced by Danish biochemist S.P.L. Sørensen (1868-1939) in 1909, from P, for Ger. Potenz "power, potency," and H, symbol of → hydrogen.

Phad (γ UMa)
Faxez (#)

Fr.: Phecda   

A blue, → main sequence star of → apparent visual magnitude 2.44 and → spectral type A0 Ve located in → Ursa Major. Other designations: Phecda; Phekda; Phegda; Phekha; Phacd.

Phad, from Ar. al-Fakhidh (ad-Dubb) (الفخذ‌الدب) "the thigh (of the Bear)".

Faxez, from Ar., as above.


Fr.: Phaéton   

A hypothetical → planet which once was postulated to have existed between the orbits of → Mars and → Jupiter and its destruction supposedly led to the formation of the → asteroid belt. The idea of such a hypothetical planet was first put forward by the German astronomer Heinrich Wilhelm Olbers (1758-1840).

In Greek mythology Phaeton was the sun god Helios. Phaeton tried to drive his father's solar chariot but crashed after almost setting fire to the whole earth.

halq (#)

Fr.: pharynx   

The tube or cavity, with its surrounding membrane and muscles, that connects the mouth and nasal passages with the esophagus ( → throat.

From Gk pharynx (genitive pharyngos) "windpipe, throat."

Halq, loan from Ar.

  ۱، ۲) فاز؛ ۳) سیما   
1, 2) fâz; 3) simâ

Fr.: phase   

1) A particular stage or point in a course, development, or graph varying cyclically; the fractional part of the period through which the time has advanced, measured from some arbitrary origin. Phase is measured like an angle, when a complete cycle is equivalent to a phase of 360° (or 2π radians), or, sometimes, as a number between 0 and 1. Two or more waves of the same frequency are → in phase when their maxima and minima take place at the same moments. Otherwise, they are said to be → out of phase or that they have a → phase difference.
2) A state in which matter can exist, depending on temperature and pressure, e.g. the → solid, → liquid, → gaseous, and → plasma states.
3) A recurring form of the → Moon or a → planet seen in the sky. → lunar phase, → phases of Venus.
4) In a → binary star system, → orbital phase.

Mod.L. phases, plural of phasis, from Gk. phasis "appearance," from stem of phainein "to show, to make appear."

1) Fâz, loanword from Fr., as above.
2) Simâ "face, aspect, resemblance."

phase angle
  زاویه‌ی ِ فاز   
zâviye-ye fâz (#)

Fr.: angle de phase   

1) Physics: Of a → periodic wave, the number of suitable units of angular measure between a point on the wave and a reference point.
2) Astro.: For an object in the solar system, the angle "Sun-object-Earth" that is, the angle between the Sun and the observer as seen from the given object. It is 0° when the object is fully illuminated, 90° when the object is half-illuminated (like the Moon at first quarter and last quarter), and 180° when the object is between Earth and the Sun.
3) More generally, the angle between star light incident onto a related revolving object and the light reflected from the object to the observer (Earth).

phase; → angle.

phase curve
  خم ِ فاز   
xam-e fâz

Fr.: courbe de phase   

1) Astro.: A curve describing the → brightness of a reflecting → natural satellite as a function of its → phase angle.
2) Math.: A plot of the solution to a set of equations of motion in a phase space as a function of time.

phase; → curve.

phase delay
  درنگ ِ فاز   
derang-e fâz

Fr.: délai de phase   

The ratio of the phase shift of a sinusoidal signal in transmission through a system to the frequency of the signal.

phase; → delay.

phase diagram
  نمودار ِ فاز   
nemudâr-e fâz

Fr.: diagramme de phases   

A graph showing the equilibrium relationships between phases (such as vapor-liquid, liquid-solid) of a chemical compound, mixture of compounds, or solution.

phase; → diagram.

phase difference
  دگرسانی ِ فاز   
degarsâni-ye fâz

Fr.: différence de phase   

The difference of phase (usually expressed as a time or an angle) between two periodic quantities which vary sinusoidally and have the same frequency.

phase; → difference.

phase equilibrium
  ترازمندی ِ فاز   
tarâzmandi-ye fâz

Fr.: équilibre de phases   

The condition of temperature and pressure under which different phases (e.g. gas, liquid, and solid) of a substance coexist.

phase; → equilibrium.

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