An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 736
rotational modulation (ROT)
  دگر‌آهنگش ِ چرخشی   
degarâhangeš-e carxeši

Fr.: modulation rotationnelle   

A very small variation in the surface brightness of a single star due to its rotation. Several types of stars are known to have photospheric spots. Brightness variation occurs as rotation carries star spots or other localized activity across the line of sight.

rotational; → modulation.

rotational motion
  جنبش ِ چرخشی   
jonbeš-e charkheshi

Fr.: mouvement de rotation   

Of a → rigid body, a motion in which there are always two points of the body which remain motionless.

rotational; → motion.

rotational period
  دوره‌ی ِ چرخش   
dowre-ye carxeš

Fr.: période de rotation   

rotation period.

rotational; → period.

rotational transition
  گذرش ِ چرخشی   
gozareš-e carxeši

Fr.: transition rotationnelle   

A slight change in the energy level of a molecule due to the rotation of its constituent atoms about their center of mass.

rotational; → transition.

rotational velocity
  تندای ِ چرخشی   
tondâ-ye catxeši

Fr.: vitesse de rotation   

The velocity of a → rotational motion; same as → angular velocity.

rotational; → velocity.

  چرخنده، چرخاننده   
carxandé (#), carxânandé (#)

Fr.: rotateur   

A device that rotates or causes rotation.

Agent noun from → rotate.

carxâ (#)

Fr.: rotor   

A rotating part of an electrical apparatus, e.g. the armature of a generator, or of a mechanical device.
A system of several flat blades attached to a hub, which rotates either horizontally to give lift and thrust to a helicopter, or vertically to help control it.
Meteo.: The circulation of flow about a horizontal or nearly horizontal axis.

Short for rotator, → rotate, + → -or.

Carxâ agent noun of carxidan, → rotate.

raj (#)

Fr.: ligne, rangée   

CCD detector: Series of pixels arranged along a line. → column

O.E. ræw "a row, line;" cf. Du. rij "row;" O.H.G. rihan "to thread," riga "line;" Ger. Reihe "row, line, series."

Raj "line, row," variants raž, rak, râk, rezg (Lori), ris, risé, radé, rasté, râsté, related to râst "right, true; just, upright, straight;" Mid.Pers. râst "true, straight, direct;" Soghdian rəšt "right;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Av. rāz- "to direct, put in line, set," razan- "order;" cf. Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" PIE base *reg- "move in a straight line," hence, "to direct, rule."

Roxburgh criterion
  سنجیدار ِ راکسبرگ   
sanjidâr-e Roxburgh

Fr.: critère de Roxburgh   

An integral constraint used to quantify the uncertainty on the extent of → convective overshooting and its effect on models of stars.

Roxburgh, I. 1989, A&A, 211, 361; → criterion.

RR Lyrae star
  ستاره‌ی ِ RR چنگ   
setâre-ye RR Cang

Fr.: étoile RR Lyrae   

A member of a large class of → pulsating stars of type A2-F6 with periods less than 1 day. They are similar to → Cepheids, except that their periods are much shorter and are less luminous. RR Lyrae stars belong to → Population II and are often found in → globular clusters (hence one of their older names cluster variables) or elsewhere in the → galactic halo. They are used as distance indicators (→ standard candle) out to more than 200 kpc.

Lyra; → star.

rubidiom (#)

Fr.: rubidium   

A metallic chemical element; symbol Rb. Atomic number 37; atomic weight 85.4678; melting point 38.89°C; boiling point 686°C; specific gravity 1.53 at 20°C. It was discovered in the mineral lepidolite by the German chemist Robert Wilhelm Bunsen and the German physicist Gustav-Robert Kirchoff in 1861. Bunsen isolated rubidium in 1863.

From L. rubidus "deep red," because of the two "deep red lines" in its spectra.

  یاقوت، یاکند   
yâqut (#), yâkand (#)

Fr.: rubis   

Red form of corundum, Al2O3, which owes its color to traces of chromium. Used in laser as a gem stone.

M.E. rubi, from O.Fr. rubi, from M.L. rubinus lapis "red stone," from L. rubeus "red," related to ruberred.

Yâqut, yâkand related to Gk. hyakinthos "hyacinth," probably ult. from a non-I.E. Mediterranean language.

Rudolphine Tables
  زیج ِ رودولفی   
zij-e Rudolfi

Fr.: Tables rudolphines   

A set of astronomical tables created in 1627 by Johannes Kepler (1571-1630) based on observations by Tycho Brahe (1546-1601). These tables allowed Kepler to derive the three laws of planetary motions bearing his name (→ Kelpler's laws). These are the first tables in which → atmospheric refraction has been taken into account. They overruled the → Prutenic Tables.

From the L. title Tabulae Rudolphinae, in memory of Rudolf II (1552-1612), king of Hungary and Bohemia, and Holy Roman Emperor; → table.

Ruffini-Horner method
  روش ِ روفینی-هورنر   
raveš-e Ruffini-Horner

Fr.: méthode de Ruffini-Horner   

A method for finding the value of a → polynomial given by a real number and deriving its → roots. It consists essentially of factoring the polynomial in a nested form. Also known as → nested multiplication.

Named after Paolo Ruffini (1765-1822) and William Horner (1786-1837), who independently elaborated the method; → method.

Ruhmkorff coil
  پیچه‌ی ِ روهمکورف   
pice-ye Ruhmkorff

Fr.: bobine de Ruhmkorff   

An → induction coil which was a forerunner of today's automobile ignition coil. It consists of two coils wound on a single → iron core, and uses an → alternating current produced by a break-wheel to induce a high-voltage current in the secondary coil.

After Heinrich Daniel Ruhmkorff (1803-1877), a German-born instrument maker, who settled in Paris in 1819 for the rest of his life; → coil.


Fr.: règle   

1) A law or regulation that governs behaviors, actions, or operations. → Arnett's rule, → commutation rule, → Fleming's rule, → Hund's rule, → left-hand rule, → Maxwell's rule, → right-hand rule, → rigorous selection rule, → selection rule, and → Trouton's rule.
2) A strip of rigid material marked off in units used especially for measuring length.
3) In some → planispheric astrolabes, a bar which rotates across the front of the astrolabe and is used to locate positions on the → rete, and to relate them to the scale of hours marked on the → limb. Also called the → index.

M.E. riule, reule, from O.Fr. riule, from L. regula "straight stick, bar, ruler," related to regere "to rule, straighten, guide;" cognate with Pers. râst "right, straight," razan "rule," as below.

Razan from Av. razan "rule, order," from rāz- "to direct, put in line, set," rasman- "the lines or files of the army;" O.Pers. rāsta- "straight, true," rās- "to be right, straight, true;" Mid.Pers. râst "true, straight, direct;" Soghdian rəšt "right," rây-, râyênitan "to arrange;" Mod.Pers. râst "right, true; just, upright, straight;" raj "line, row," variants raž, rak, râk, rezg (Lori), radé, râdé "line, rule, row," rasté, râsté "row, a market with regular ranges of shops;" ris, risé "straight;" cf. Skt. raj- "to direct, stretch," rjuyant- "walking straight;" Gk. orektos "stretched out;" L. regere "to lead straight, guide, rule," p.p. rectus "right, straight;" PIE base *reg- "move in a straight line," hence, "to direct, rule."

rule of decision
  رزن ِ واسون   
razan-e vâsun

Fr.: régle de décision   

Same as → significance testing and → test of significance.

rule; → decision.

rule of three
  رزن ِ سه   
razan-e sé

Fr.: règle de trois   

Te method of finding the fourth term in a proportion when three terms are given.

rule; → three.

ruled grating
  توری ِ شیاردار   
turi-ye šiyârdâr

Fr.: réseau à traits   

A → diffraction grating with a series of grooves that have been ruled on a reflective surface with a diamond tool mounted on a ruling machine. Ruled gratings may have triangular or trapezoidal groove profiles, whereas → holographic gratings usually have sinusoidal groove profiles.

Ruled, → rule; → grating.

Turi, → grating; šiyârdâr "having grooves," from šiyâr, → groove, + -dâr "having, possessor," → property.

ruled surface
  رویه‌ی ِ خط‌ساخته   
ruye-ye xatt sâxté

Fr.: surface réglée   

A surface, such as a cylinder or cone, that can be generated by moving a straight line.

Ruled, p.p. of rule; → surface.

Ruyé, → surface; xatt sâxté "built, formed by a line," from xattline; sâxté, p.p. of sâxtan "to build, make, fashion; to adapt, adjust, be fit" (from Mid.Pers. sâxtan, sâz-, Manichean Parthian s'c'dn "to prepare, to form;" Av. sak- "to understand, to mark," sâcaya- (causative) "to teach").

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