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

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.

A measure of the blurring and degradation of the image of astronomical objects caused by → turbulence in the Earth's atmosphere, including the telescope environment. Seeing causes the images of stars to break up into → speckle patterns, which change very rapidly with time. See also → Fried parameter; → differential image motion monitor.

→ see; → -ing.

Šekân "wrinkle, plait; curl; rupture, breach," variant of šekan "fold, curl; ripples on water," from šekastan "to break, split;" Mid.Pers. škastan "to break;" Av. scind-, scand "to break, cleave;" Proto-Iranian *skand- "to break, cleave;" PIE sken- "to cut off."

The angular size of a stellar image for long exposures, as determined by the ratio λ/r₀, where λ is the wavelength and r₀ the typical size of → turbulence patches. → Fried parameter. The most common seeing measurement is the → full-width at half-maximumof the seeing disk. → Airy disk.

→ seeing; → disk.

An optical instrument that follows the variation of → atmospheric turbulence by continuously measuring the → seeing conditions.

→ seeing; → monitor.

1) Of a line, that portion bounded by two points.
2) Of a circle, that portion of a plane bounded by an arc of the circle and its chord.
3) Of a sphere, the solid formed between two parallel planes that cut through a sphere.
4) In computer science, a portion of a program, often one that can be loaded and executed independently of other portions.

From L. segmentum "a strip or piece cut off," originally a geometric term, from secare "to cut" + -mentum "-ment."

Borank, from Kermâni borang "a slice (of fruit);" Borujerdi boleng "piece, section," ultimately from *brin-ka- (probable contracted forms Lari peng and pengi "portion or part of anything"), related to boridan "to cut off;" Mid.Pers. brīn-, blyn-, britan, brinitan "to cut off," Av. brī- "to shave, shear," brin- (with prefix pairi-); cf. Skt. bhrī- "to hurt, injure," bhrinanti "they hurt;" PIE base bhrei- "to cut, pierce."

A large telescope mirror consisting of smaller mirror segments designed to act as a single, larger reflecting surface. Because current monolithic mirrors cannot be constructed larger than about eight meters in diameter, the use of segmented mirrors is a key component for larger aperture telescopes.

Segmented, p.p. of → segment (v.); → mirror.

To separate or set apart from others or from the main body or group; isolate.

From M.E. segregat, from L. segregatus, p.p. of segregare "separate from the flock, isolate, divide," from se- "apart from" + greg-, ablative of grex, gregis "herd, flock, crowd," cf. Gk. gergera "swarm, flock;" maybe related to Old Khotanese -gris- in hamgris- "to assemble."

Savâyidan, from savâ "separate, apart;" probably related to Mid.Pers. s'w- "to crush," sây- "to rub, wear, tear;" cf. Kurd. (Hawramân) sawa, Roshani sêw-/sêwt, Bartangi siw-/siwd, Yazghulani saw-/sed, Bajui sâw-/sâwd "to rub, smear, grind" (Cheung 2007); Mod.Pers. sây-/sudan "to rub, wear, tear, grind, dissolve;" cf. Skt. śā- "to sharpen, whet."

The act or practice of segregating. The state or condition of being segregated. → mass segregation.

Verbal noun of → segregate.

Of, subject to, or caused by → vibrations of the → Earth. → seismic wave.

From seism, → seismo-, + → -ic.

An → elastic wave generated in the → Earth by an → impulse such as an → earthquake or an → explosion. Seismic waves may travel either along or near the Earth's surface or through the Earth's interior.

→ seismic; → wave.

A combining form meaning "earthquake;" → seismology, → seismograph, etc.

From Gk. seismo- combining form of seismos "shock, earthquake," from seiein "to shake."

Larzé-, from larzé "shaking, trembling," from larzidan "to tremble, shiver;" Mid.Pers. larzidan "to shake, tremble;" Manichean Mid.Pers. rarz- "to shiver with fever;" Proto-Iranian *rarz- "to shake, tremble."

An instrument that detects, magnifies, and records → seismic waves, especially those caused by → earthquakes or → explosions.

→ seismo-; → -graph.

The branch of geophysics that is concerned with the study of earthquakes and measurement of the mechanical properties of the Earth.

→ seismo-; → -logy.