An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 1067
photoelectric heating
  گرمایش ِ شید-برقی   
garmâyeš-e šid-barqi

Fr.: chauffage photoélectrique   

A heating process occurring in → diffuse molecular clouds which is believed to be the main heating mechanism in cool → H I regions. Far-ultraviolet (FUV) photons, in the energy range 6 eV <hν < 13.6 eV, expel electrons from → interstellar dust grains and the excess → kinetic energy of the electrons is converted into gas → thermal energy through → collisions. The high energy limit corresponds to the cut-off in the → far-ultraviolet (FUV) radiation field caused by the hydrogen absorption (hν = 13.6 eV), while the low energy limit corresponds to the energy needed to free electrons from the grains (hν ~ 6 eV). In the cold neutral medium (Tkin≥ 200 K) photoelectric heating accounts for most of the heating, the → X-ray and → cosmic ray heating rates (→ cosmic-ray ionization) being more than an order of magnitude smaller. In a relatively dense neutral medium (nH≥ 100 cm-3), where a significant fraction of carbon is in the neutral form, carbon ionization becomes an important heating source, but it is still not comparable to the photoelectric effect. The heating rate cannot be directly measured, but it can be estimated through observations of the [C II] line emission, since this is believed to be the main → coolant in regions where the photoelectric heating is dominant (See, e.g., Juvela et al., 2003, arXiv:astro-ph/0302365).

photoelectric; → heating.

photoelectric magnitude
  بُرز ِ شید-سنجیک، ~ نور-سنجیک   
borz-e šidsanjik, ~ nursanjik

Fr.: magnitude photoélectrique   

The magnitude of an object as measured with a photoelectric photometer.

photoelectric; → magnitude.

photoelectric photometry
  شید-سنجی ِ شید-برقی   
šidsanji-e šidbarqi

Fr.: photométrie photoélectrique   

A photometry in which the magnitudes are obtained using a photoelectric photometer.

photoelectric; → photometry.

photoelectron
  شید-الکترون، نور-الکترون   
šid-elektron, nur-elektron

Fr.: photoélectron   

An electron emitted from an atom or molecule by an incident photon in the → photoelectric effect.

photo-; + → electron.

photoemissive effect
  اسکر ِ شید-گسیلی   
oskar-e šid-gosili

Fr.: effet photoémissif   

The emission of electrons as a result of incident radiation in the → photoelectric effect. Also called → external photoelectric effect.

photo- + → emissive; → effect.

photoevaporation
  شید-بخارش، نور-بخارش   
šidboxâreš, nurboxâreš

Fr.: photoévaporation   

A process going on in a molecular cloud surface whereby the surface material ionized by ultraviolet photons of neighboring stars is dissipated.

photo- + → evaporation.

photoexcitation
  شید-بر‌انگیزش   
šid-barangizeš

Fr.: photoexcitation   

The mechanism of raising an electron to higher energies by photon absorption, when the energy of the photon is too low to cause photoionization.

photo- + → excitation.

photograph
  عکس، شید-نگار، نور-نگار   
aks, šidnegâr, nurnegâr

Fr.: photographie   

A picture produced by photography. → picture.

From → photo- + → -graph.

Aks, from Ar. 'aks "to inverse, reverse." Šidnegâr, nurnegâr, from šid, nur, → photo-, + negâr, → graph.

photographic magnitude
  بُرز ِ عکسبرداریک   
borz-e aksbardârik

Fr.: magnitude photographique   

The apparent magnitude of a star as determined by measuring its brightness on a photographic plate. The photographic magnitude scale is now considered obsolete.

Adj. of → photography; → magnitude.

photographic survey
  بردید ِ عکسبرداریک   
bardid-e aksbardârik

Fr.: relevé photographique   

Recording a large area of the night sky by photographic techniques, as practiced in the past before the advent of electronic detectors.

Adj. of → photography; → survey.

photography
  عکسبرداری، شید-نگاری، نور-نگاری   
aksbardâri, šidnegâri, nurnegâri

Fr.: photographie   

The process of recording and producing images by exposing light-sensitive detectors to light or other forms of radiation.

photo-, → -graphy.

Aksbardâri, literally "taking photograph," from aks, → photograph, + bardâri verbal noun of bardâštan "to take," composite verb from bar- "on; up; upon; in; into; at; forth; with; near; before; according to" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + dâštan "to have, to possess" (Mid.Pers. dâštan; O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind;" cf. Skt. dhr-, dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE *dher- "to hold, support").
Šidnegâri, nurnegâri, action noun from šidnegâr, nurnegâr, → photograph.

photoionization
  شید-یونش، نور-یونش   
šid-yoneš, nur-yoneš

Fr.: photoionisation   

The physical process in which an incident high-energy photon ejects one or more electrons from an atom, ion, or molecule.

photo- + → ionization.

photoionize
  شید-یونیدن، نور-یونیدن   
šid-yonidan, nur-yonidan

Fr.: photoioniser   

To cause, or to undergo → photoionization.

photo-; → ionize.

photoionized
  شید-یونیده، نور-یونیده   
šid-yonidé, nur-yonidé

Fr.: photoionisé   

Subject to, or produced by → photoionization.

photo-; → ionized.

photoluminescence
  شید-فروزستی   
šid-foruzesti

Fr.: photoluminescence   

A process in which → absorption of photons at → ultraviolet (UV) / → optical wavelengths is followed by → electronic transitions associated with the emission of longer wavelength optical and → near-IR photons. Photoluminescence has two types: → phosphorescence and → luminescence. The excitation of the photoluminescence process under astrophysical conditions results from the absorption of a single UV/optical photon, leading to an electronic transition from a → ground state (1) to a higher state (2). State (2) typically is a bound, high-lying vibrational-rotational level of the first or second electronically excited state of a molecule or molecular ion, or a high state in the → conduction band of a semiconductor particle. The excited system relaxes through a series of → vibrational-rotational transitions until the electron finds itself in an intermediate state (3), from where an optical electronic transition back to the ground state (1) is possible. In a → polycyclic aromatic hydrocarbon (PAH) molecule, for example, state (3) can either be the lowest state in the → singlet or → triplet vibrational-rotational manifold of the first excited electronic level (Witt, A. N., Vijh, U. P., 2003, astro-ph/0309674).

photo-; → luminescence.

photometer
  شید-سنج، نور-سنج   
šidsanj, nursanj

Fr.: photomètre   

An instrument for measuring the amount of light.

photo- + → -metry.

photometric
  شید-سنجی، شید-سنجیک، نور-سنجی، نور-سنجیک   
šidsanji, šidsanjik, nursanji, nursanjik

Fr.: photométrique   

Pertaining to or related to → photometry.

photometer + → -ic.

photometric band
  باند ِ شیدسنجیک، ~ نورسنجیک   
bând-e šid-sanjik, ~ nur-sanjik

Fr.: bande photométrique   

The range of → wavelengths allowed by a → filter used in a → photometric system.

photometric + → band.

photometric binary
  دُرین ِ شید-سنجیک، ~ نور-سنجیک   
dorin-e šidsanjik, ~ nursanjik

Fr.: binaire photométrique   

A binary star whose binarity is detectable from its variability and light-curve that has certain specific characteristics.

photometric + → binary.

photometric calibration
  کبیزش ِ شید-سنجیک، ~ سنور-سنجیک   
kabizeš-e šidsanjik, ~ nursanjik

Fr.: calibration photométrique   

A calibration which converts the measured relative magnitudes into an absolute photometry.

photometric + → calibration.

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