An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 703
radiative transfer equation
  هموگش ِ تراوَژ ِ تابش   
hamugeš-e tarâvaž-e tâbeš

Fr.: équation de transfer radiatif, ~ ~ de rayonnement   

The equation that describes the → radiative transfer. It states that the → specific intensity of radiation Iσ during its propagation in a medium is subject to losses due to → extinction and to → gains due to → emission: dIσ/dx = - μσ . Iσ + ρ . jσ, where x is the coordinate along the → optical path, μσ is the → extinction coefficient, ρ is the mass → density, and jσ is the → emission coefficient per unit mass.

radiative; → transfer; → equation.

radiative transition
  گذرش ِ تابشی   
gozareš-e tâbeši

Fr.: transition radiative   

A transition between two states of an atomic or molecular entity, the energy difference being emitted or absorbed as photons.

radiative; → transition.

radiative zone
  زنار ِ تابشی   
zonâr-e tâbeši

Fr.: zone radiative   

The region of a star in which the energy generated by → nuclear fusion in the core is transferred outward by → electromagnetic radiation and not by → convection. Such zones occur in the interior of low-mass stars, like the Sun, and the envelopes of → massive star. The radiative zone of the Sun starts at the edge of the core of the Sun, about 0.2 solar radii, and extends up to about 0.7 radii, just below the → convective zone.

radiative; → zone.

radiatively driven wind
  باد ِ تابشی   
bâd-e tâbeši

Fr.: vent radiatif   

Same as → radiation-driven wind

radiative; → drive; → wind.

  ریشه، ریشگی، ریشال   
rišé (#), rišegi (#), rišâl

Fr.: racine   

1) Math.: The indicated root of a quantity, as denoted by an expression written under the → radical sign.
2) Chemistry: A group of atoms present in a series of compounds which conserves its identity in the course of chemical changes which affect the rest of the molecule. For example, the → cyano radical and → hydroxyl group.

M.E., from L.L. radicalis "of or having roots," from → radix "root."


radical axis
  آسه‌ی ِ پایه   
âse-ye pâyé

Fr.: axe radical   

Of two circles, the straight line containing all points P such that the lengths of the tangents from P to the two circles are equal.

radical; → axis.

radical sign
  نشانه‌ی ِ ریشال، ~ ریشگی   
nešâne-ye rišâl, ~ rišegi

Fr.: signe radical   

The symbol √ placed before a number or quantity to indicate the extraction of the square root. The value of a higher (the n-th) root is indicated by a raised positive digit (n) in front of the symbol, as in 3√ (cube root). The first known occurrence of this symbol was in the book Die Cross, published in 1525, by the German mathematician Christoff Rudolff.

radical; → symbol.

  ۱)؛ ۲) رادیو؛ ۳) پرتو، رادیو   
1); 2) râdio; 3) partow, râdio

Fr.: radio   

1) An apparatus for receiving or transmitting radio broadcasts.
2) Pertaining to the → radio waves of the → electromagnetic radiation.
3) As a prefix, indicating → radition or → radioactivity.

1); 2) Short from radiophone and radio-telegraphy.
3) Combining form of → radiation.

Râdio, loan from Fr., as above; partowray.

radio Arc
  کمان ِ رادیویی   
kamân-e râdio-yi

Fr.: arc radio   

A large number of narrow filaments in → radio continuum occurring toward the → Galactic Center, about 15 to 20 arc-minutes (some 50 parsecs in projection) north of → Sgr A*. The radio Arc is the prototype of → non-thermal filaments (NTFs) and resolves into a set of more than a dozen vertical filaments with lengths of about 30 pc distributed symmetrically with respect to the → Galactic equator (Yusef-Zadeh et al. 1984, Nature 310, 557). Among more than 100 NTFs found in the Galactic center region, the Arc is the only one known to show inverted spectrum with a → spectral index α = +0.3 (Law et al. 2008, ApJS 177, 515, and references therein). This implies a very hard energy spectrum of particles for a source of → synchrotron radiation.

radio; → arc.

radio astronomy
  رادیو-اخترشناسی، اخترشناسی ِ رادیویی   
râdio axtaršenâsi, axtaršenâsi-ye râdioi

Fr.: radio astronomie   

The branch of astronomy that deals with the study of the Universe by means of → radio waves.

radio; → astronomy.

radio burst
  بلک ِ رادیویی   
belk-e râdio-yi

Fr.: sursaut radio   

A burst of emission in the radio frequencies of the electromagnetic spectrum.

radio; → burst.

radio continuum emission
  گسیل ِ پیوستار ِ رادیویی   
gosil-e peyvastâr-e râdio-yi

Fr.: émission de continuum radio   

A → continuum emission with frequencies in the radio range of the electromagnetic spectrum.

radio; → continuum; → emission.

radio counterpart
  همتای ِ رادیویی   
hamtâ-ye râdio-yi

Fr.: contrepartie radio   

The representation of an object in radio wavelengths while it has emission in other parts of the electromagnetic spectrum.

radio; counterpart, from O.Fr. contrepartie, from contre "facing, opposite," → counter-, + partie "copy of a person or thing," originally feminine p.p. of partir "to divide."

Hamtâ "counterpart, resembling, equal," from ham- "together, with; same, equally, even" (Mid.Pers. ham-, like L. com- and Gk. syn- with neither of which it is cognate. O.Pers./Av. ham-, Skt. sam-; also O.Pers./Av. hama- "one and the same;" Skt. sama-; Gk. homos-; originally identical with PIE numeral *sam- "one," from *som-. The Av. ham- appears in various forms: han- (before gutturals, palatals, dentals) and also hem-, hen-) + "fold, plait, ply; piece, part," also a multiplicative suffix; Mid.Pers. tâg "piece, part;" → radio.

radio emission
  گسیل ِ رادیویی   
gosil-e râdio-yi

Fr.: émission radio   

Electromagnetic radiation carried by → radio waves.

radio; → emission.

radio flux
  شار ِ رادیویی   
šârr-e râdioyi

Fr.: flux radio   

Total radiation in radio wavelengths going out from the 2π solid angles of a hemisphere. → flux.

radio; → flux.

radio flux density
  چگالی ِ شار ِ رادیویی   
cagâli-ye šârr-e râdioyi

Fr.: densité de flux radio   

The flux of → radio waves that falls on a → detector per → unit → surface area of the detector per unit → bandwidth of the radiation per unit → time. The unit is → jansky.

radio; → flux; → density.

radio frequency
  بسامد ِ رادیویی   
basâmad-e râdio-yi (#)

Fr.: fréquence radio   

The → electromagnetic radiation with the frequency range between 3 → kiloherz (kHz) to 300 → gigahertz (GHz). See also → radio wave.

radio; → frequency.

radio galaxy
  رادیو-کهکشان، کهکشان ِ رادیویی   
râdio kahkešân, kahkešân-e râdioyi

Fr.: radiogalaxie   

A galaxy that is extremely luminous at radio wavelengths between 10 MHz and 100 GHz. The radio luminosity of a strong radio galaxy (1037-1039 watts) can be up to a million times greater than the radio output of an ordinary galaxy and up to a hundred times greater than the optical luminosity of a galaxy such as the Milky Way. The optical counterparts of radio galaxies are usually an → elliptical galaxy. Radio galaxies often exhibit jet structure from a compact nucleus. They typically display two → radio lobes that are often approximately aligned with the jets observed in the optical and that may extend for millions of → light-years.

radio; → galaxy.

radio interferometer
  اندرزنش‌سنج ِ رادیویی   
andarzanešsanj-e râdioyi

Fr.: interféromètre radio   

An → interferometer designed for radio frequencies.

radio; → interferometer.

radio jet
  رادیو-شان، شان ِ رادیویی   
radio-šân, šân-e râdioyi

Fr.: jet radio   

An → astrophysical jet appearing in the radio wavelengths of the electromagnetic spectrum.

radio; → jet.

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