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: 13116 Search : far
photon noise
  نوفه‌ی ِ فوتون   
nufe-ye foton

Fr.: bruit de photons   

An intrinsic noise caused by the quantum nature of light. Same as → quantum noise.

photon; → noise.

photon sphere
  سپهر ِ فوتون   
sepehr-e foton

Fr.: sphère de photons   

A surface where if a photon is emitted from one of its points the photon follows a closed orbit and returns periodically to its departure point. Such a surface exists only near sufficiently → compact objects where the → curvature of → space-time is very important. In other words, a body can take a stable orbit around a → black hole provided that it moves with the → speed of light. However, only photons can have such a velocity; hence the term "photon sphere." For a non-rotating → Schwarzschild black hole, the photon sphere has a radius of R = 3GM/c2 = 3 RS/2, where G is the → gravitational constant, M is the mass, c is the → speed of light, and RS is the → Schwarzschild radius. For a rotating, → Kerr black hole, the situation is much more complex due to the → Lense-Thirring effect. In that case circular paths exist for radii whose values depend on the rotation direction. More specifically, in the equatorial plane there are two possible circular light paths: a smaller one in the direction of the rotation, and a larger one in the opposite direction.

photon; → sphere.

photon tiring limit
  حد ِ خستگی ِ فوتون   
hadd-e xastegi-ye foton

Fr.: limite par fatigue du photon   

The maximum → mass loss rate of a star when the → wind luminosity equals the total available → stellar luminosity. The mechanical luminosity of the wind at infinity is given by: Lwind = Mdot (v2/2 + GM/R) = Mdot (v2/2 + vesc2/2). For Lwind = L*, the mass loss rate is Mdotmax = 2L*/(v2 + vesc2). Following Owoki & Gayly (1997), Mdottir is the maximum mass loss rate when the wind just escapes the gravitational potential, with v tending toward zero. Mdottir is much larger than typical mass loss rates from → line-driven winds, where the driving lines become saturated with increasing density limiting the wind mass loss rates to about 10-4 Msun yr-1 in even the most luminous stars.

photon; tiring, from tire "to weary; become weary," → tired; → limit.

photon-baryon plasma
  پلاسما فوتون-باریون   
plâsmâ foton-bâriyon

Fr.: plasma photon-baryon   

The plasma filling space before the → recombination epoch that mainly consisted of → cosmic microwave background radiation photons, electrons, protons, and → light elements.

photon; → baryon; → plasma.

photonics
  فوتونیک   
fotonik

Fr.: photonique   

The technology of generating and harnessing light and other forms of radiant energy whose quantum unit is the photon. The science includes light emission, transmission, deflection, amplification and detection by optical components and instruments, lasers and other light sources, fiber optics, electro-optical instrumentation, related hardware and electronics, and sophisticated systems.

photon + → -ics.

photosphere
  شیدسپهر، رخشان‌سپهر   
šidsepehr, raxšânsepehr

Fr.: photosphère   

1) The visible surface of the Sun (temperature 5700 K), just below the → chromosphere and just above the → convective zone. The solar photosphere is a thin layer of roughly 300 km wide. Its temperature decreases uniformly with height, from about 6,600 K (pressure 0.868 → millibars) at its bottom, to about 4,400 K (pressure 125 mb), where it merges with the chromosphere. The photosphere has a "rice-grain" appearance, called → granulation, caused by rising (hot) and falling (cool) material in the → convective cells just below the photosphere. Other main features of the photosphere are → sunspots, → faculae, and → supergranulation.
2) The region of a star which gives rise to the continuum radiation emitted by the star.

photo- + → sphere.

photospheric
  شیدسپهری   
šidsepehri (#)

Fr.: photosphérique   

Of or pertaining to a → photosphere.

photosphere; → -ic.

photosynthesis
  شیدهندایش   
šidhandâyeš

Fr.: photosynthèse   

The process in green plants, algae, diatoms, and certain forms of bacteria by which carbohydrates are synthesized from carbon dioxide and water using light as an energy source. Most forms of photosynthesis release oxygen as a byproduct.

photo- + → synthesis.

photovisual magnitude
  بُرز ِ شیدچشمی   
borz-e šidcašmi

Fr.: magnitude photovisuelle   

Magnitude defined for the combination of a photographic plate and a yellow filter, approximating the spectral sensitivity of the eye.

photo- + → visual; → magnitude.

photovoltaic detector
  آشکارگر ِ شید-ولتایی   
âškârgar-e šidvoltâyi

Fr.: détecteur photovoltaïque   

A detector usually constituted by a p-n junction. Upon irradiation, the electron-hole pairs which are created, are immediately separated by the strong electric field across the junction, and a current is generated, which is proportional to the number of incident photons per second.

photo- + → voltaic; → detector.

phrase
  وتپار   
vatpâr

Fr.: locution, expression   

A sequence of two or more words arranged in a grammatical construction and acting as a unit in a → sentence.

From L.L. phrasis "diction," from Gk. phrasis "speech, way of speaking, enunciation," from phrazein "to express, tell," from phrazesthai "to consider."

Vatpâr, literally "part of speech," from vat-, "to speak, say;" cf. (Kurd.) wittin "to speak, say," → letter, + pâr "piece, part, portion," → partial.

physical
  فیزیکی   
fiziki (#)

Fr.: physique   

Pertaining to the physical sciences, especially physics.

physics + → -al.

physical adsorption
  برشم ِ فیزیکی   
baršam-e fiziki

Fr.: adsorption physique   

Same as → physisorption.

physical; → adsorption.

physical chemistry
  شیمی ِ فیزیکی   
šimi-ye fiziki (#)

Fr.: chimie physique   

The branch of chemistry dealing with the relations between the physical properties of substances and their chemical composition and transformations.

physical; → chemistry.

physical condition
  بوتار ِ فیزیکی   
butâr-e fiziki

Fr.: condition physique   

The state of a → physical system regarding its temperature, density, pressure, etc. at a given time.

physical; → condition.

physical constant
  پایای ِ فیزیکی   
pâyâ-ye fiziki (#)

Fr.: constante physique   

A fundamental → physical quantity that is generally believed to be both universal in nature and constant in time.

physical; → constant.

physical dimension
  وامون ِ فیزیکی   
vâmun-e fiziki

Fr.: dimension physique   

Any of basic physical quantities, such as mass, length, time, electric charge, and temperature in terms of which all other kinds of quantity can be expressed.

physical; → dimension.

physical law
  قانون ِ فیزیکی   
qânun-e fiziki (#)

Fr.: loi physique   

A theoretical principle which is deduced from particular observational facts regarding the behavior of matter. Physical laws are expressed by a general statement that a particular → physical phenomenon always occurs if certain → conditions are present.

physical; → law.

physical libration
  هلازان ِ فیزیکی، رخگرد ِ ~   
halâzân-e fiziki, roxgard-e ~

Fr.: libration physique   

A real periodic variation in the rotation rate of a celestial object, as distinct from a → geometrical libration. In particular, slight oscillations in the → Moon's rotation caused by the → gravitational attraction of the Earth on the → equatorial bulge of the Moon's near side. The Moon's physical libration is about 0.03° in longitude and about 0.04° in latitude.

physical; → libration.

physical optics
  نوریک ِ فیزیکی   
nurik-e fiziki

Fr.: optique physique   

The branch of optics concerned with the wave properties of light, → diffraction, → polarization, and other phenomena for which the ray approximation of → geometric optics is not valid. Also called → wave optics.

physical; → optics.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc coh col col col Com com com com com com com com Com con con con con con con con con con con con con coo Cor Cor cor cos cos cos Cou cou Cra Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg ura uti val var vec Vel ver Ver vie Vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>