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

A sudden, violent gust of wind, often accompanied by rain, snow, or sleet. A sudden increase of the mean wind speed which lasts for several minutes at least before the mean wind returns to near its previous value. It is often accompanied by rain or snow.

Probably from a Scand. source (cf. Norw. skval "sudden rush of water," Sw. skvala "to gush, pour down").

Bâdzad, from bâd, → wind + zad past stem of zadan "to strike, beat; to do; to play an instrument" (Mid.Pers. zatan, žatan; O.Pers./Av. jan-, gan- "to strike, hit, smite, kill" (jantar- "smiter"); cf. Skt. han- "to strike, beat" (hantar- "smiter, killer"); Gk. theinein "to strike;" L. fendere "to strike, push;" Gmc. *gundjo "war, battle;" PIE *g^when- "to strike, kill").

1) A rectangle having all four sides of equal length.
2) The second power of a quantity, expressed as a² = a × a, where a is the quantity. → inverse square law.

M.E., from O.Fr. esquire "a square, squareness," from V.L. *exquadra, from *exquadrare "to square," from L. → ex- "out" + quadrare "make square," from quadrus "a square," from quattuor→ four.

Câruš, from Av. caθruša- "four sides (of a four-sided figure)", from caθru- "four," Mod.Pers. cahâr, câr "four" + uša- "angle," Mod.Pers. guš, gušé.

A solid angle whose cone is a tetrahedral pyramid with an angle between its edges equal to 1°. 1 square degree = 3.046 x 10^-4 sr = 2.424 x 10^-5 solid angle of a complete sphere.

→ square; → degree.

An international project to construct a highly sensitive radio interferometer array operating between 0.15 and 20 GHz with an effective collecting area of one square kilometer. The number of individual telescopes will be 2000 to 3000. SKA will have a sensitivity 100 times higher than that of today's best radio telescopes and an angular resolution < 0.1 arcsec at 1.4 GHz. The site will be selected in 2012 and early science with Phase 1 is scheduled for from 2016 on. See also the SKA homepage.

→ square; → kilometer; → array.

A → matrix with equal numbers of → rows and → columns (i.e., an n × n matrix).

→ square; → matrix.

A large → asterism of four stars, approximately square in shape, in the northern sky. Three of the stars, → → Markab, → Scheat, and → Algenib, belong to the constellation → Pegasus. The fourth, → Alpheratz, was lost to Pegasus when the constellation boundaries were formalised, and now lies just within the borders of → Andromeda.

→ square; → Pegasus.

Chahârguš, → tetragon; → Pegasus.

Quantity which when multiplied by itself produces another quantity.

→ square; → root.

An oscillation which alternatively assumes, for equal lengths of time, one or two fixed values.

→ square; → wave.

Same as → quadrature of the circle

→ square; → wave.

The mathematical problem of subdividing a square into a number of smaller squares, all of different sizes.

→ square; → square.

In → supersymmetry theories, a hypothetical → boson super-partner of a → quark. See also → slepton.

s from → supersymmetry; → quark.

A → close binary star lying at the center of the → supernova remnant W50, in → Aquila, about 18,000 → light-years away. The system consists of a normal → O star or → B star in a 13.087 day orbit around a compact object that is either a → neutron star or a → black hole. Material transferred from the normal star into an → accretion disk surrounding the compact object is ejected in two jets of ionized gas in opposite directions, at about a quarter of the speed of light. The system is also a periodic X-ray source. The jets are emitted in a cone with a half-angle of about 20°. The cone is inclined by 80° to the line of sight. The compact object precesses with a period of 164 days. This causes the projected angle of the jets to go through a 164 day cycle, giving the variation in the Doppler shifts.

Such called because this object carries number 433 in the Stephenson-Sanduleak catalog of stars with strong emission lines, compiled by Bruce Stephenson and Nicholas Sanduleak in 1977.

A condition in which a dynamical system slightly displaced from its equilibrium configuration always tends to return to this configuration. → instability, → instability strip.

Noun from adj. → stable.

Physics: 1) Having the ability to react to a disturbing force by maintaining or regaining position or condition.
2) Incapable of becoming a different isotope or element by radioactive decay.

M.E., from O.Fr. estable, from L. stabilis "firm, steadfast," literally "able to stand," from stem of stare "to stand;" cognate with Pers. istâdan "to stand" (Mid.Pers. êstâtan; O.Pers./Av. sta- "to stand, stand still; set;" Av. hištaiti; cf. Skt. sthâ- "to stand;" Gk. histemi "put, place, weigh," stasis "a standing still;" L. stare "to stand;" Lith. statau "place;" Goth. standan; PIE base *sta- "to stand").

Pâydâr "stable, firm" literally "having feet," from pâ(y) "foot; step" (Mid.Pers. pâd, pây; Av. pad- "foot;" cf. Skt. pat; Gk. pos, genitive podos; L. pes, genitive pedis; P.Gmc. *fot; E. foot; Ger. Fuss; Fr. pied; PIE *pod-/*ped-) + dâr present stem of dâštan "to have, hold, maintain, possess" (Mid.Pers. dâštan; O.Pers./Av. root dar- "to hold, keep back, maintain, keep in mind;" cf. Skt. dhr-, dharma- "law;" Gk. thronos "elevated seat, throne;" L. firmus "firm, stable;" Lith. daryti "to make;" PIE *dher- "to hold, support").

An equilibrium state of a system in which if a small perturbation away from equilibrium is applied, the system will return to its equilibrium state. An example is a pendulum hanging straight down. If it is pushed slightly, it will experience a force back toward the equilibrium position. It may oscillate around the equilibrium position for a while, but it will finally regain its equilibrium position. → unstable equilibrium.

→ stable; → equilibrium.

A nuclide that is not → radioactive and therefore does not spontaneously undergo → radioactive decay.

→ stable; → nuclide.

1) A long stick used to help in walking. → Sharafeddin's staff.
2) A body of persons, as employees, charged with carrying out the work of an establishment or executing some undertaking. → staff astronomer.

M.E. staf; O.E. stæf "walking stick, rod used as a weapon, pastoral staff;" sense of "group of military officers that assists a commander" attested from 1702; cf. O.N. stafr, M.Du. staf, O.H.G. stab, Ger. Stab, M.Du. stapel "pillar, foundation;" PIE base *stebh- "to support, place firmly on, fasten; post, stem;" cognate with Av. stabra- "strong, firm" and other Iranian words, as below.

1) Cubdast "hand stick," from cub "staff, stick," Mid.Pers. côp "wood, stick" + dast, → hand.
2) Estab, from Av. stabra- "strong, firm;" O.Pers. sta^mb- "to revolt;" Mid.Pers. stabr "strong, firm;" Mod.Pers. ustâm "column" [Steingass], Lori esi "tent pole," setabr "strong, big, thick, dense," setanbé "strong, powerful," estam, setam "oppression;" cf. Skt. stabh- "support," stambh- "to support, fix firmly;" Gk. stephein "to tie around, encircle," astemphes "firm, rigid;" Lith. stebas "staff, pillar."

A professional astronomer who works within a specified observatory or research group.

→ staff; → astronomer.

A single step or phase in an ongoing process.

M.E., from O.Fr. estage "a story or floor of a building, stage for performance," from V.L. *staticum "a place for standing," from L. statum, p.p. of stare "to stand."

Gâmé, from gâm "step, pace" (related to âmadan "to come"); Mid.Pers. gâm "step, stride, pace;" O.Pers. gam- "to come; to go;" Av. gam- "to come; to go," jamaiti "goes;" cf. Skt. gamati "goes;" Gk. bainein "to go, walk, step;" L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE stem *gwem- "to go, come."

The state or condition of not flowing or running. → stagnation point, → stagnation pressure.

L. stagnatum, stagnatus, p.p. of stagnare "to stagnate," from stagnatum "standing water," from PIE root *stag- "to seep drip."

Nâravâni, literally "not flowing," from nâ- negation prefix, → un-, + ravân "flowing, running," pr.p. of raftan "to go, walk; to flow;" (Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack").