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

A sphere containing a polyhedron (such as a pyramid) all of whose vertices lie on the surface of the sphere. The polyhedron so contained is said to be inscribed in the sphere.

Circumscribed p.p. of → circumscribe; → sphere.

Surrounding or revolving around the Sun, such as circumsolar space, circumsolar dust.

Circumsolar, from → circum- + → solar.

Watchful and discreet; cautious; prudent:

→ circum-; → suspect.

Circumspect observation or action; caution; prudence.

→ circumspect.

A condition or fact attending an event and having some bearing on it.

L. circumstantia "surrounding condition," neut. pl. of circumstans, pr.p. of circumstare "to stand around," from → circum- + stare "to stand" from PIE *sta- "to stand."

Pirâstâd, from pirâ-, → circum-, + âstâd, istâd "standing," from istâdan "to stand," Mid.Pers. êstâtan, O.Pers./Av. sta- "to stand, stand still; set," Av. hištaiti, cf. Skt. sthâ- "to stand," âsthâ- "condition, circumstance," Gk. histemi "put, place, weigh," stasis "a standing still," L. stare "to stand."

Surrounding or occurring around a star.

Circumstellar, from → circum- + → stellar.

Any concentration of material in the form of a disk orbiting around a star. → accretion disk; → protoplanetary disk.

→ circumstellar; → disk.

Interstellar → dust grains localized around various types of stars, such as → asymptotic giant branch stars. Circumstellar dust occurs in the form of a spherical shell or a disk and is at the origin of an → infrared excess for the central star. See also → circumstellar matter.

→ circumstellar; → dust.

A very extensive envelope of cold gaseous materials surrounding evolved cool stars, notably → red giants, → red supergiants (→ Mira variables), or → asymptotic giant branch stars. The typical size of such envelopes is several thousands times that of the stellar radius and their temperature ranges from 1000 to10 K. Circumstellar envelopes result from mass loss from the central star (10^-7 to 10^-4→ solar masses per year) and expand with moderate velocities (10 to 15 km sec^-1). The low temperature of the envelope is at the origin of the formation of molecules, which in certain conditions provide → maser emission (H₂O, OH, SiO). Similarly, dust grains form in the envelope produce an → infrared excess emission.

→ circumstellar; → envelope.

The circumstances or physical conditions related to the immediate surroundings of a star.

→ circumstellar; → environment.

A zone around a star within which a planet can have temperatures that permit liquid water, depending on the luminosity of the star and the distance of the planet from it.

→ circumstellar; → habitable zone.

Maser emission from molecules in the circumstellar envelopes of → red giants, and also from regions around → protostars.

→ circumstellar; → maser.

Dust, gas and plasma around stars, generally present in the form of stellar winds or nebulae ejected by the stars.

→ circumstellar; → matter.

A stream of matter into the interstellar medium from a central star.

→ circumstellar; → outflow.

A shell of dust, molecules, and neutral gas around an evolved star resulting from an intensive mass loss phase, such as the asymptotic giant branch phase for low- and intermediate mass stars and LBVs or supernovae for massive stars.

→ circumstellar; → shell.

A colorful halo centered on the zenith, appearing when the solar elevation above the horizon is not too high (< 32°).

→ circum-; → zenithal; → arc.

Lying between the Earth and the orbit of the Lune. → translunar.

L. cis, cistra "on this side," cf. Gk. ekeinos "that person," E. he, it, O.H.G. he.

Insuumâhi, insumângi, from insu "this side," from in "this" + su "side" + mâhi, mângi→ lunar, → moon.

Any large town or populous place.

M.E. cite, from O.Fr. cite "town, city," from L. civitas "citizenry; community," from civis "native, townsman;" related to L. cuna "cradle; bed;" Gk. kome "village;" Skt. śiva- "auspicious, dear;" O.E. ham "dwelling, house, village;" E. home; Ger. Heim (→ hamlet); Iranian dialects kiye "house, home;" Xonsâri ki "house;" Anâraki xiya, Tâti Karingân kâ, Sangesari keh "house, home;" PIE *kei- "to lie; bed."

Šahr "city," from Mid.Pers. šahr "land, country, city;" O.Pers. xša- "to rule," pati-xša- "to have lordship over," Xšyāršan- "hero among kings" or "ruling over heroes" the proper name of the Achaemenid emperor Helenized as Xerxes, upari.xšay- "to rule over," xšāyaθiya- "king;" Mid.Pers. šâh "king," pâdixšâ(y) "ruler; powerful; authoritative;" Mod.Pers. šâh "king," pâdšâh "protecting lord, emperor, monarch, king," šâyestan "to be worth, suit, fit;" Av. xšā(y)- "to rule, have power," xšayati "has power, rules," xšāyô "power;" cf. Skt. ksā- "to rule, have power," ksáyati "possesses;" Gk. ktaomai "I acquire," ktema "piece of property;" PIE base *tkeh- "to own, obtain."

Of or relating to citizens and their interrelations with one another or with the state.

M.E., from L. civilis "of or proper to a citizen," from civis "citizen, townsman," from PIE *kei- "to lie, homestead;" → city.

Šârin, from šâr "city," variant šahr; Mid.Pers. šahr "city, country, land" (O.Pers./Av. xšaθra- "kingship, kingdom," (Skt. ksatra-), from xšay-, "to rule;" cf. Skt. ksayati "possesses;" Gk. ktaomai "I acquire," ktema "piece of property") + -in suffix of adjectives, relations and agent nouns (as in qamin "sorrowful," nušin "sweet, agreeable (thing)."

→ Mean solar time.

→ civil; → time.