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: 13176 Search : in
radial migration
  کوچ ِ شعاعی   
kuc-e šo'â'i

Fr.: migration radiale   

The process whereby a → disk star changes its → galactocentric distance. Radial migration involves → angular momentum transfer, resulting from → resonances created by transient → density waves such as → bars or → spiral arms in → galactic disks. According to → galactic dynamics models, → churning is the main cause of radial migration. Radial migration of stars plays an important role in shaping the properties of galactic disks.

radial; → migration.

radial motion
  جنبش ِ شعاعی   
jonbeš-e šo'â'i

Fr.: mouvement radial   

A motion away from or toward a central point or axis.

radial; → motion.

radial spoke
  پره‌ی ِ شعاعی   
parre-ye šoâyi

Fr.: spoke radial   

Any of short-lived (generally lasting less than 24 hours) radial features that periodically appear over the outer half of → Saturn's → B ring, when the ring tilt angle is small. These features revolve at the same rate as the planet's → magnetic field and maintain their shape over much of the course of their existence even though they extend tens of thousands of kilometers across the rings. It is believed that the tiny particles that make up these spokes are electrically charged and temporarily "frozen" into the planet's magnetic field (Ellis et al., 2007, Planetary Ring Systems, Springer).

radial; → spoke.

radial velocity
  تندای ِ شعاعی   
tondâ-ye šo'â'i

Fr.: vitesse radiale   

The component of a three-dimensional velocity vector of an object directed along the line of sight. It is measured by examining the Doppler shift of lines in the spectrum of astronomical objects.

radial; → velocity.

radial velocity curve
  خم ِ تندای ِ شعاعی   
xam-e tondâ-ye šo'â'i

Fr.: courbe de vitesse radiale   

A curve describing the variation of the radial velocity of a star, due to the Doppler effect, under the gravitational effect of a secondary body (companion or exoplanet). The amplitude of these variations depends upon the mass of the secondary and its distance from the star.

radial velocity; → curve.

radial velocity method
  روش ِ تندای ِ شعاعی   
raveš-e tondâ-ye šo'â'i

Fr.: méthode de vitesses radiales   

The technique based on the analysis of the → radial velocity curve, used to detect the presence of an invisible secondary around a host star. This method holds the majority of exoplanet discoveries.

radial velocity; → method.

radian
  رادیان   
râdiyân (#)

Fr.: radian   

A unit of angular measure; one radian is that angle with an intercepted arc on a circle equal in length to the radius of the circle.

From radi(us) + -an an originally adj. suffix.

radiance
  تابش‌مندی   
tâbešmandi

Fr.: luminance   

1) Generally, the → radiant energy per unit → solid angle per unit of → projected area of the → source. It is usually expressed in → watt per → steradian per → square  → meter (W m-2 sr-1). Same as steradiancy.
2) Of any particular → wavelength within the interval covered by a → spectral line, the → energy per unit → surface per steradian, per wavelength; denoted Iλ. The term radiance is often loosely replaced by "→ intensity." The radiance of the whole line is given by I = ∫ Iλ dλ. The radiance of an → emission line depends, among other things, upon the → number of → atoms per unit area in the → line of sight (the → column density) in the → upper level of the line.

From radia(nt), → radiant, + → -ance.

Tâbešmandi, noun from tâbešmand "possessing radiation," from tâbeš, → radiation, + -mand a suffix denoting possession; Mid.Pers. -ômand suffix forming adjectives of quality.

radiant
  ۱) تابنده، تابشی؛ ۲) تابسر   
1) tâbandé, tâbeši; 2) tâbsar

Fr.: radiant   

1) Sending out rays of light; bright; shining.
See also: → radiant energy, → radiant flux, → radiant intensity.
2) The point in the sky from which → meteors in a → meteor shower appear to radiate or come. See also: → radiant drift.

M.E., from M.Fr. radiant, from L. radiantem (nominative radians) "shining," pr.p. of radiare "to shine, radiate," → radiation.

1) Tâbandé, tâbeši adj. from tâbidan, → radiate.
2) Tâbsar, from tâb "light, radiation," → radiation, + sar "head, top, summit, point," → head.

radiant drift
  دلک ِ تابسر   
delek-e tâbsar

Fr.: dérive de radiant   

The apparent slow motion of the → radiant of a → meteor shower from night to night against the background stars due to the Earth moving in its orbit around the Sun.

radiant; → drift.

radiant energy
  کاروژ ِ تابشی   
kâruž-e tâbeši

Fr.: énergie radiative   

The energy that is transmitted in the form of → radiation, in particular as → electromagnetic radiation.

radiant; → energy.

radiant flux
  شار ِ تابشی   
šâr-e tâbeši (#)

Fr.: flux radiatif   

Rate of flow of energy as → radiation.

radiant; → flux.

radiant intensity
  درتنویی ِ تابشی   
dartanuyi-ye tâbeši

Fr.: intensité de rayonnement   

A measure of the amount of radiation emitted from a point expressed as the radiant flux per unit solid angle leaving this source.

radiant; → intensity.

radiate
  تابیدن   
tâbidan (#)

Fr.: rayonner   

To send out → energy, such as → heat or → light, in the form of → rays or → waves.

From L. radiat(us), p.p. of radiare "to shine, to beam" + -ate verbal suffix.

Tâbidan, variants tâftan "to shine," tafsidan "to become hot;" Mid.Pers. tâftan "to heat, burn, shine;" taftan "to become hot;" Parthian t'b "to shine;" Av. tāp-, taf- "to warm up, heat," tafsat "became hot," tāpaiieiti "to create warmth;" cf. Skt. tap- "to heat, be/become hot; to spoil, injure, damage; to suffer," tapati "burns;" L. tepere "to be warm," tepidus "warm;" PIE base *tep- "to be warm."

radiation
  تابش   
tâbeš (#)

Fr.: radiation, rayonnement   

The emission of any → rays, → waves, or → particles from a source; usually applied to the → emission of → electromagnetic energy.

Verbal noun of → radiate.

radiation belt
  کمربند ِ تابش، ~ تابشی   
kamarband-e tâbeš (#), ~ tâbeši (#)

Fr.: ceinture de radiations   

A ring-shaped region in the → magnetosphere of a planet in which charged particles are trapped by the planet's magnetic field. The radiation belts surrounding Earth are known as the → Van Allen belts.

radiation; → belt.

radiation constant
  پایای ِ تابش   
pâypa-ye tâbeš

Fr.: constante de rayonnement   

Same as → radiation density constant.

radiation; → constant.

radiation damping
  میرایی ِ تابشی   
mirâyi-e tâbeši

Fr.: amortissement par rayonnement   

Damping of a system which loses energy by → electromagnetic radiation.

radiation; → damping.

radiation density constant
  پایای ِ چگالی ِ تابش   
pâypa-ye cagâli-ye tâbeš

Fr.: constante de rayonnement   

The constant related to the total energy radiated by a → blackbody and defined as: a = 4σ/c, where σ is the → Stefan-Boltzmann constant and c the → speed of light. Its value is a = 7.5657 x 10-15 erg cm-3 K-4. Same as → radiation constant.

radiation; → density; → constant.

radiation era
  دوران ِ تابش   
dowrân-e tâbeš

Fr.: ère du rayonnement   

The epoch in the history of the Universe, lasting from the → Big Bang until about 400,000 years later, when the temperature had dropped to 109 K and the rate of electron-positron → pair annihilation exceeded the rate of their production, leaving radiation the dominant constituent of the Universe. The radiation era was followed by the → matter era.

radiation; → era.

<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB 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 con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl 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 > >>