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

Instability caused by a slow dissipation of energy.

→ secular; → instability.

The angle subtended at a star by a baseline that is the distance the Sun moves in a given interval of time with respect to the local standard of rest (4.09 AU per year).

→ secular; → parallax.

A variation of planetary orbital elements which is always in the same direction as time increases.

→ secular; → perturbation.

1) The condition in which the equilibrium configuration of a system is stable over long periods of time.
2) The condition of a star when it is stable against arbitrary adiabatic perturbations.

→ secular; → stability.

In perturbation theory used in celestial mechanics, a steadily increasing disturbance. → periodic term.

→ secular; → term.

Same as → secular perturbation.

→ secular; → variation.

The view that religious considerations should be excluded from civil affairs or public education.

→ secular.

The process of organizing society or aspects of social life around non-religious values or principles.

Verbal noun of secularize "giyânidan" (گیانیدن); → secular

1) Free from or not exposed to danger or harm; safe.
2) To get hold or possession of; procure; obtain.

From L. securus "free from care, quiet, easy," also "careless, reckless;" of things, "free from danger, safe," from *se cura, from se "without, free from," + cura, → care.

Zilé, from Tabari zil, zilé "firm, fixed," zil hâkerdan "to fix, fasten," of unknown origin.

1) Freedom from care, anxiety, or doubt; well-founded confidence.
2) Something that secures or makes safe; protection; defense.
3) A department or organization responsible for protection or safety (Dictionary.com).

→ secure; → -ity.

A technique that uses → spectral energy distribution results from models to reproduce observational data.

→ spectral energy distribution; → fitting.

Mineral or organic material which has been transported and deposited by an agent of erosion such as water, wind, and ice.

From Fr. sédiment, from L. sedimentum "a settling, sinking down," from stem of sedere "to settle, sit"

Nehešt past stem of neheštan "to place, deposit," from ne- "down, below," → ni- (PIE), + heštan "to place, put" from Mid.Pers. hištan, hilidan "to let, set, leave, abandon;" Parthian Mid.Pers. hyrz; O.Pers. hard- "to send forth," ava.hard- "to abandon;" Av. harəz- "to discharge, send out; to filter," hərəzaiti "releases, shoots;" cf. Skt. srj- "to let go or fly, throw, cast, emit, put forth;" Pali sajati "to let loose, send forth."

Of, pertaining to, or of the nature of sediment.

Adj. of → sediment.

A rock composed of materials that were transported to their present position by wind or water. → Sandstone, → shale, and → limestone are sedimentary rocks.

→ sedimentary; → rock.

A trans-Neptunian object (numbered 90377) and a likely → dwarf planet, it is the most distant large object yet found orbiting the Sun. It is at present over 90 A.U.s away, 3 times as far as Pluto. Its precise diameter is unknown, probably 1,600-2,200 km (about 12-17% of Earth). Its estimated orbital period is 12,050 years. Formerly known as 2003 VB12

In Inuit mythology, Sedna (Inuktitut Sanna) is a goddess of the marine animals, especially mammals such as seals.

The second phase in the evolution of a → supernova remnant (SNR) occurring after the → free expansion phase. After the passage of the → reverse shock, the interior of the SNR is so hot that the energy losses by radiation are very small (all atoms are → ionized, no → recombination). The expansion is driven by the → thermal pressure of the hot gas and can therefore be regarded as → adiabatic; the → cooling of the gas is only due to the → expansion. Pressure forces accelerate the swept-up → interstellar medium (ISM) converting → thermal energy (which came from original explosion) into → kinetic energy of the → shell of swept-up mass. As the mass of the ISM swept up by the shell increases, it eventually reaches densities which start to impede the free expansion. → Rayleigh-Taylor instabilities arise once the mass of the swept-up ISM approaches that of the ejected material. This causes the SNR's ejecta to become mixed with the gas that was just shocked by the initial → shock wave. The Sedov-Taylor phase lasts some 10⁴ years and is followed by the radiative or → snowplow phase. Also called → adiabatic phase.

After Sedov, L. (1959, Similarity and Dimensional Methods in Mechanics, New York, Academic Press) and Taylor, G. I. (1950, Proc. Roy. Soc. London, A, 201, 159 and 175); → phase.

To perceive with the eyes; look at.

M.E. seen, from O.E. seon "to see, look, behold, understand, know," ultimately from PIE *sek^w- "to see, notice;" cognate with Du. zien "to see," Ger. sehen "to see," Danish, Swedish and Norwegian Bokmal se "to see," L. signum "mark, token."

Didan "to see, regard, catch sight of, contemplate, experience;" Mid.Pers. ditan; O.Pers. dī- "to see;" Av. dā(y)- "to see," didāti "sees;" cf. Skt. dhī- "to perceive, think, ponder; thought, reflection, meditation," dādhye; Gk. dedorka "have seen."

An → electromotive force produced in a closed electric circuit formed by connecting conductors of different metals in series when the two junctions junctions are maintained at different temperatures. The circuit constitutes a → thermocouple.

Named for the German physicist Thomas Seebeck (1770-1831), who discovered the effect; → effect.

A small single crystal of a semiconductor from which is grown the large single crystal for the manufacture of semiconductor devices.

O.E. sed, sæd; cf. O.N. sað, O.S. sad, O.Fris. sed, M.Du. saet, O.H.G. sat, Ger. Saat; PIE base *se- "to sow."

Toxm "seed" (Tabari tim "seed; race," Laki tôm "seed"), from Mid.Pers. tôhm, tôhmak, tôm, tuxm "seed; extraction; descent;" Av. taoxman- "seed;" O.Pers. taumī:- "family;" cf. Skt. tókman- "offspring, children, race, child," tokma- "young shoot, young blade of corn."

A nucleus from which a variety of → fusion  → chain reactions derive in → stellar nucleosynthesis.

→ seed; → nucleus.