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: 12948 Search : far
photometric parallax
  دیدگشت ِ شیدسنجیک   
didgašt-e šidsanjik

Fr.: parallaxe photométrique   

A method of deriving the distance of a star using its → apparent magnitude and the → absolute magnitude inferred from its → spectral type.

This is a misnomer, because the method has nothing to do with parallax; → photometric; → parallax.

photometric system
  راژمان ِ شید-سنجیک، ~ نور-سنجیک   
râžmân-e šidsanjik, ~ nursanjik

Fr.: système photométrique   

A system of → magnitudes, each of them characterized by a set of well-defined → passbands (or → filters) with known → response curves. The system is defined by the values given for the → standard stars. See also:
AB magnitude system, → five-color system, → Stromgren system, → JHK system, → UBV system, → uvby system.

photometric; → system.

photometry
  شید-سنجی، نور-سنجی   
šidsanji, nursanji

Fr.: photométrie   

In astronomy, the measurement of the light of astronomical objects, generally in the visible or infrared bands, in which a wavelength band is normally specified.

photo- + → -metry.

photomultiplier
  شید-بستاگر، نور-بستاگر   
šid-bastâgar, nur-bastâgar

Fr.: photomultiplicateur   

Electronic tube which converts photons into electrons, multiplies the electrons via a series of electrodes, and produces a measurable current from a very small input signal.

photo- + → multiplier.

photon
  فوتون   
foton (#)

Fr.: photon   

The → quantum of the → electromagnetic field, which mediates the interaction between charged particles. It is the mass-less → boson with zero → electric charge, which propagates with the → speed of light in vacuum. The energy of a photon is connected to its → frequency ν, through the formula E = hν, where h is → Planck's constant.

From phot-, variant of → photo- before a vowel + → -on a suffix used in the names of subatomic particles (gluon; meson; neutron), quanta (photon, graviton), and other minimal entities or components. The term photon was coined by Gilbert N. Lewis in 1926 in a letter to the editor of Nature magazine (Vol. 118, Part 2, December 18, page 874).

photon escape time
  زمان ِ گریز ِ فوتون   
zamân-e goriz-e foton

Fr.: temps d'échappement des photons   

The time required for a photon created in the Sun's core to attain the → photosphere and leave the Sun. If the photons were free to escape, they would take a time of only R/c (a couple of seconds) to reach the surface, where R is the Solar radius and c the speed of light. The solar material is, however, very opaque, so that photons travel only a short distance before interacting with other particles. Therefore, photons undergo a very large number of → random walks before arriving at the surface by chance. The typical time is approximately 5 x 104 years for a constant density Sun.

photon; → escape; → time.

photon hardening
  سختش ِ فوتون   
saxteš-e foton

Fr.: durcissement des photons   

An effect occurring in the outer zones of → H II regions where the number of high-energy ultraviolet photons with energies well above the → ionization potential of hydrogen increases with respect to the number of → Lyman continuum photons. The effect is due to stronger absorption of weaker photons.

hard; → photon.

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.

<< < -es -iv -ti 21- A r abe abs abs acc acc acc act act ada adi adu aff age alc Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app aps arc Arg ari art ass ast ast ast atm ato att aur aut axi B r bac Bal Bar Bar Bay bec Ber Bet Bie bij bin bio bis bla bla blu blu bol Bor bou Bra bre bro Bug C-s cal Cam can car Car Cas cat cav cel cen cer Cha cha cha che cho cir cir cir cla clo clo clu coa coe coh col col col com com com com com com com com com 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 dar dat daw de- Deb dec dec dee def deg del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis div dog Dop dou dra dua dus dwa dyn e-m ear ecl eco eff ein Ein elb ele ele ele ele Els emi emp ene enr env epi equ equ Eri est Euc eva evo exc exc exh exo exp exp ext ext f-n Fah fam fau fee Fer fib fil fin fir fix fle flu foc for for for fra fre fre fri fun fuz gal gal gal Gan gau GCN gen geo geo geo geo Gl glo gra gra gra gra gra gre gro GW1 hab hal han HAR haz hea hel hel Hen Her heu Hig Hil hol hop hor hou Hub Hum Hyd hyd hyd hyp hys ide ign ima imp imp inc inc ind ine inf inf inf inh INP ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jos Jun K2 Kep key kin Kol lag lam Lan lar las lav lea leg len lev lig lim lin lin lin lis lob loc log lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal mar mas mas mat max mea mea mee Men mer met met met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxy pal pan par Par par par pas pea Pen per per per per per pet pha pho pho pho phy pie Pit Pla pla pla pla ple Poi pol pol pol pol pop pos pos pow pre pre pre Pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua Qui rad rad rad rad rad rad ram ran rat rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev rho Rie rim riv rol Ros rot rul S a Sah san Sat sca Sch Sch scr sec sec sec sei sel sem sep set sha she sho sid sig sil sim sin sit sky slu sno sof sol sol sol sol sou sou spa spa spe spe spe sph spi spl spr sta sta sta sta sta ste ste sti sto str str sub sub sub sug sun sup sup sup sup sur syl syn sys tal Tay tel ten ter tex the the the thi tho thu tid tim tod top tot tra tra tra tra tri tri tro tru tur twi Typ UFO ult unc uni uni uni upg ura uti val var vec vel ver ver vig vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yel you zer zod > >>