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

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").

A point where the → flow  → velocity is → zero. For example a point around an obstacle where a → flow tube splits into two portions.

→ stagnation; → point.

The sum of → static pressure and → dynamic pressure in the → Bernoulli equation.

→ stagnation; → pressure.

An uncastrated adult male horse, especially one used for breeding.

M.E. stalon, from O.Fr. estalon, "uncastrated male horse," cognate with O.H.G. stal "stable," cf. O.H.G. stall "stand, place, stable, stall," Ger. Stall "stable," Stelle "place"), from PIE root *stel- "to put, stand," with derivatives referring to a standing object or place; akin to Pers. istâdan "to stand," → station.

Nariyân, from nar "male," → masculine.

To have or maintain an upright position, supported by one's feet; rise to one's feet (OxfordDictionaries.com).

M.E. standen, from O.En. standan "occupy a place; stand firm; stay, be, exist; oppose, resist attack; stand up, be on one's feet;" cognate with O.Norse standa, O.Saxon and Gothic standan, O.H.G. stantan, Du. staan, Ger. stehen, cognate with Pers. istâdan, as below.

Istâdan "to stand," from 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."

Any set of conditions that describe the normal, desired, or ideal state of something, and that serves a basis for representing or evaluating actual examples of this thing.

M.E., from O.Fr. estandart "banner, standard," probably from Frankish *standord; cf. Ger. Standort "standing-point," from standan "to stand," cognate with Pers. istâdan, as below, with the second component conformed to -ard.

Estândé, literally "made stand, fixed," p.p. istândan transitive verb of istâdan, "to → stand."

A hypothetical vertical distribution of atmospheric temperature, pressure, and density that, by international agreement, is taken to be representative of the atmosphere for purposes of pressure altimeter calibrations, aircraft performance calculations, aircraft and missile design, ballistic tables, etc.

→ standard; → atmosphere.

An astronomical object, belonging to some class, that has a known luminosity. In principle, by comparing the known luminosity to the observed brightness, the distance to the object can be derived. The four major primary distance indicators are Cepheids, supernovae, novae, and RR Lyrae variables. The secondary distance indicators include H II regions, globular clusters, brightest red and blue stars. → primary calibrator; → secondary calibrator.

→ standard; → candle.

The conventional → Big Bang model, which is based on two assumptions: the → cosmological principle of homogeneity and isotropy leading to the → Robertson-Walker metric, and → Einstein's field equations of general relativity along with familiar properties of matter. This model is a remarkably successful operating hypothesis describing the evolution of the Universe from 1/100 second after the initial event through to the present day. It provides explanations for several basic problems such as: → Hubble's law of recession of galaxies, interpreted in terms of the expansion of the Universe; the abundances of the → light elements, in excellent agreement with the predictions of → primordial nucleosynthesis; and the thermal spectrum and angular isotropy of the → cosmic microwave background (CMB) radiation, as expected from a hot, dense early phase of expansion. For a non-standard model, see → ekpyrotic Universe.

→ standard; → cosmology.