An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 452
frame dragging
  کرّه‌ی ِ چارچوب، چارچوب-کرّه   
kerre-ye cârcub, cârcub-kerré

Fr.: entraînement des repères, effet Lense-Thirring   

The alteration in the → free fall motion of a test → mass in the presence of a massive → rotating object, as compared to the identical case of a non-rotating object. This dragging of → inertial frames is predicted by → general relativity. Also called → Lense-Thirring effect.

frame; → drag.

frame frequency
  بسامد ِ تصویر   
basâmad-e tasvir

Fr.: fréquence image   

The number of times per second that the frame is scanned in television. Also known as picture frequency.

frame; → frequency.

frame of reference
  چارچوب ِ بازبرد   
câcub-e bâzbord

Fr.: système de référence   

A set of axes to which positions and motions in a system can be referred.

frame; → reference.


Fr.: cadrage   

The process of adjusting a television picture to a desired position in the direction of progression.

From → frame + → -ing.

Cârcubeš, verbal noun of cârcubidan, from cârcubframe.

frânsiom (#)

Fr.: francium   

An extremely rare radioactive chemical element; symbol Fr. Atomic number 87; atomic weight of most stable isotope 223; melting point about 27°C; boiling point about 677°C. Its most stable isotope (half-life about 22 minutes) occurs naturally, to a very limited extent, in uranium minerals. More than 30 other isotopes of francium are known; some are prepared by bombarding thorium with protons, deuterons, or alpha particles.

From France, where the French physicist Marguerite Perey (1919-1975) discovered it in 1939 in the alpha particle decay of actinium.

Fraunhofer line
  خط ِ فراؤنهوفر   
xatt-e Fraunhofer

Fr.: raie de Fraunhofer   

One of many absorption lines and bands in the spectrum of the Sun. The most prominent features are labeled with capital letters A to K, starting at the red end. The A and B bands are now known to be caused by absorption in Earth's atmosphere, while the rest are due to absorption in the Sun's → photosphere. C and F are now better known as H-alpha and H-beta (→ Balmer series); the → D lines are of sodium, the → H and K lines of calcium, and the G band of neutral iron and the interstellar → CH (methylidine) molecule.

Named after Joseph von Fraunhofer (1787-1826), German optician and physicist, who discovered these lines in 1814; → line.

Fraunhofer's refractor
  شکست‌گر ِ فراؤنهوفر   
šekastgar-e Fraunhofer

Fr.: réfracteur de Fraunhofer   

The first modern refracting telescope which had an outstanding quality. It was built in 1824 by Fraunhofer for the Russian Imperial Observatory in Dorpat, now Tartu in Estonia. It had a 23-cm → achromatic lens and a German-type → equatorial mounting driven by a clockwork. Wilhelm Struve (1793-1864) used the refractor to observe many → visual binaries, and attempted to measure the distances of stars through their visual → parallaxes. He also obtaibned accurate values for the diameters of the → Galilean satellites of → Jupiter.

Named after Joseph von Fraunhofer (1787-1826), German optician and physicist; → refractor.

âzâd (#)

Fr.: libre   

Not physically bound by something.
free atmosphere, → free body, → free charge, → free electron, → free expansion phase, → free fall, → free flow, → free occurrence, → free oscillation, → free radical, → free system, → free-bound emission, → free-fall time, → free-floating object, → free-free emission, → freedom, → bound-free transition, → force-free magnetic field, → Gibbs free energy, → Helmholtz free energy, → mean free path, → universality of free fall.

From M.E. fre, O.E. freo "free, exempt from," also "noble, joyful;" cf. Ger. frei, Du. vrij; ultimately from PIE *prijos "dear, beloved;" cf. Av. frāy- "to satisfy, propitiate," friθa- "beloved; dear," friθô.tara- "more beloved," Mod.Pers. fari "happy, fortunate, blessed; pleasing, good," Skt. priyá- "beloved, wished for;" Gk. praos "mild, gentle."

Âzâd "free," from Mid.Pers. âzât "free, noble;" Av. āzāta- "high-born, noble," from zan- "to bear, give birth to a child, be born," infinitive zazāite, zāta- "born," āsna- "innate, natural;" cf. Skt. janati "begets, bears;" Gk. gignesthai "to become, happen," genes "born;" L. gignere "to beget;" PIE base *gen- "to give birth, beget."

free atmosphere
  جو ِ آزاد، هواسپهر ِ ~   
javv-e âzâd, havâsepehr-e ~

Fr.: atmosphère libre   

That part of the atmosphere where the effects of the ground on the → turbulence conditions are negligible.

free, → atmosphere.

free body
  جسم ِ آزاد   
jesm-e âzâd (#)

Fr.: corps libre   

A → rigid body not constrained with other bodies and which from any given position can be displaced in any direction in space. Opposite of → constrained body.

free; → body.

free charge
  بارِ آزاد   
bâr-e âzâd

Fr.: charge libre   

An electric charge which is not held by another charge, in contrast to a → bound charge.

free; → charge.

free electron
  الکترون ِ آزاد   
elektron-e âzâd (#)

Fr.: électron libre   

An electron that is not attached to an → atom, → molecule, or → ion and is free to move under the influence of a present electric or magnetic field.

free; → electron.

free expansion phase
  فاز ِ سپانش ِ آزاد   
fâz-e sopâneš-e âzâd

Fr.: phase d'expansion libre   

The first phase of → supernova remnant (SNR) evolution in which the surrounding → interstellar medium (ISM) has no influence on the expansion of the → shock wave, and the pressure of the interstellar gas is negligible. The shock wave created by the → supernova explosion moves outward into the interstellar gas at highly → supersonic speed. Assuming that most of the → supernova energy  ESN is transformed into → kinetic energy of the ejected gas, the ejection velocity ve can be estimated from ESN by using ESN = (1/2) Meve2, which leads to ve = (2ESN / Me)(1/2), where Me is the ejected mass. The schematic structure of the SNR at this phase can be described as follows: behind the strong → shock front which moves outward into the ISM, compressed interstellar gas accumulates forming a → shell of interstellar gas. This shell of swept-up material in front of shock does not represent a significant increase in the mass of the system. After some time the accumulated mass equals the ejected mass of stellar material, and it will start to affect the expansion of the SNR. By definition, this is the end of the free expansion phase, and the corresponding radius of the SNR, called → sweep-up radius, RSW, is defined by Me = (4π/3) RSW3ρ0, that is RSW = (3Me / 4πρ0)(1/3), where ρ0 is the initial density of the ISM. This radius is reached at the sweep-up time tSW = RSW/ve. The free expansion phase lasts some 100-200 years until the mass of the material swept up by the shock wave exceeds the mass of the ejected material. Then the following → snowplow phase starts.

free; → expansion; → phase.

free fall
  افت ِ آزاد   
oft-e âzâd (#)

Fr.: chute libre   

The motion of a body under the influence of → gravity alone. See also → free-fall time.

free; → fall.

free flow
  تچان ِ آزاد   
tacân-e âzâd

Fr.: écoulement libre   

A fluid flow which develops when density differences within the fluid are the only driving forces. See also → forced flow.

free; → flow.

free occurrence
  رخداد ِ آزاد   
roxdâd-e âzâd

Fr.: occurrence libre   

An → occurrence of a → variable in a → wff, → iff it is not a → bound occurrence.

bound; → occurrence.

free oscillation
  نَوِش ِ آزاد   
naveš-e âzâd

Fr.: oscillation libre   

Oscillation of any system in stable equilibrium under the influence of internal forces only, or of a constant force originating outside the system, or of both.

free; → oscillation.

free radical
  رادیکال ِ آزاد   
râdikâl-e âzâd

Fr.: radical libre   

A chemical radical that can exist independently from atoms or group of atoms.

free; → radical.

free system
  راژمان ِ آزاد   
râžmân-e âzâd

Fr.: système libre   

A → mechanical system if all of its constituent particles or bodies can occupy arbitrary points in space or have arbitrary velocities. Otherwise, it is called a → constrained system.

free; → system.

free-bound emission
  گسیل ِ آزاد-بندیده   
gosil-e âzâd-bandidé

Fr.: émission libre-liée   

The radiation emitted when a → free electron is captured by an → ion. See also: → free-free emission; → bound-free transition.

free; → bound; → emission.

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