An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

A device that rotates or causes rotation.

Agent noun from → rotate.

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.

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."

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.

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.

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.

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 ruber→ red.

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

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.

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.

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.

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."

Same as → significance testing and → test of significance.

→ rule; → decision.

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

→ rule; → three.

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.

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 xatt→ line; 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").

The hind part of the body of an animal, as the hindquarters of a quadruped or sacral region of a bird (Dictionary.com).

M.E. rumpe, from Scandinavian; compare Dan., Norw. Swed. rumpe rumpa "tail;" cognate with Ger. Rumpf "body, trunk."

Kapal, maybe from Ar. kafal.
Sorin, → buttock.

An interval or period during which something, as a machine, operates or continues operating. → observing run.

Run, noun from verb, from M.E. ronnen, alteration of rinnen, (from O.E. rinnan and O.N. rinna) and of rennen, from O.N. renna; akin to O.H.G. rinnan; Ger. rinnen "to flow, run;" Skt. rinati "he causes to flow," and probably to L. rivus "stream;" PIE base *rei- "to flow."

Dâv "a move, a turn (at play)," dâv zadan (kardan) "to make a move (at game)," variant dow (e.g. dow bé dast-e kasi oftâdan), maybe related to dow "run," from davidan, dav- "to run;" Mid.Pers. dawidan, daw- "to run;" cf. Skt. dhāv- "to walk, hurry, flow," dhāvati "flows, runs;" Gk. thoos "fast, quick;" O.E. deaw; E. dew; PIE base *dheu- "to flow."

A massive, young, and hot star that is moving quickly through space. Runaways are probably propelled through space from a binary star when its companion has exploded as a supernova, or ejected from a stellar cluster by the dynamical interactions in the system.

→ run; away, from O.E. aweg, earlier on weg "on from this (that) place;" → star.

Setâré, → star; gorizân present participle of goriz-, gorixtan "to escape; to flee, run away;" Mid.Pers. virextan; Proto-Iranian *vi-raik, from vi- "apart, asunder" + *raik; Av. raek- "to leave, set free, let off;" Mid./Mod.Pers. reg/rig (in mordé-rig "inheritance"); Skt. ric- "to leave," rinakti "gives up, evacuates;" Gk. leipein "to leave;" L. linquere "to leave;" from PIE *linkw-, from *leikw- "to leave behind" (cf. Goth. leihvan; O.E. lænan "to lend;" O.H.G. lihan "to borrow;" O.N. lan "loan").

The water or other liquids that drains or flows from the land into streams and rivers, eventually into seas.

From → run + → off.

Ravânâb, literally "flowing water," from ravân "flowing, running," pr.p. of raftan "to go, walk; to flow" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack" + âb, → water.

Breaking apart or bursting. → plastic, → plasticity.

From L. ruptura "the breaking (of an arm or leg), fracture," from p.p. of rumpere "to break."

Pâregi "rupture," from pâré, → partial; gosast, → Big Rip.