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

The path of a object in → circular motion.

→ circular; → orbit.

The → polarization of an → electromagnetic radiation in which the electric field vector describes a circle about the direction of propagation at any point in the path of the radiation. Circular polarization is a combination of two perpendicular → linearly polarized waves that are 90 degrees out of phase with each other. Circular polarization may be referred to as "right-hand" or "left-hand," depending on the rotation direction as viewed by the observer.

→ circular; → polarization.

Circular band-pass interference filter whose thickness and central wavelength vary along the perimeter. They are used in low-resolution spectrophotometers mainly in the infra-red.

→ circular; → variable; → filter.

Light exhibiting → circular polarization.

→ circular; → polarized; → light.

The continuous movement of something from place to place or in an enclosed space. → meridional circulation.

M.E. circulacioun, from M.Fr. circulation or directly from L. circulationem, from circulare "to form a circle," from circulus "small ring," → circle.

Parhuneš, verbal noun from parhunidan, from parhun, → circle.

L. prefix meaning "around, round about."

From L. circum "around," accusative of circus "circle, ring," from Gk. kirkos, krikos "ring," PIE *sker-, *ker- "to turn, bend."

Pirâ- "around, about," variants par-, fer-, pâl- (as in ferdows, pardis, pâliz, from Av. pairidaeza- "enclosure, park"); Mid.Pers. pêrâ; O.Pers. pariy "around, about;" Av. pairi "around, over;" cf. Skt. pari; Indo-Iranian *pari- "around;" Gk. peri "around, about, beyond;" L. per "through;" PIE base *per- "through, across, beyond." The word paradize, with various forms in European languages, is a loan from Av. pairidaeza- "enclosure, park" (other Av. examples: pairifrâsa- "asking round about," pairivâra- "circumvallation").

Of or relating to an object that revolves around a → binary system.

→ circum- + → binary.

A relatively thin structure of matter composed mainly of gas and dust that orbits both the → primary and → secondary stars in → binary systems.

→ circumbinary; → disk.

An → accretion disk formed around a → black hole.

→ circum-; → black; → hole.

In a triangle, the point where the perpendicular bisectors of the triangle's sides converge.

→ circum-; → center.

A circle which passes through all three vertices of a triangle Also "Circumscribed circle".

→ circum-; → circle.

1) The boundary line of a circle.
2) The boundary line of a figure, area, or object.

From M.E., from O.Fr. circonference, from L. circumferentia, from circumferens, circumferent-, pr.p. of circumferre "to carry around," from → circum- + ferre "to carry," from PIE root *bher-; "to carry;" cf. Av./O.Pers. bar- "to bear, carry," barəθre "to bear (infinitive)," barəθri- "a female that bears (children), a mother," Mod.Pers. bordan "to carry," Skt. bharati "he carries," Gk. pherein, P.Gmc. *beranan (O.H.G. beran, Goth. bairan "to carry").

Pirâmun, from Mid.Pers. pêrâmôn, from O.Pers./Av. mâ-, mây- "to measure," from PIE *me- "measure," cf. Skt. mati "measures," matra "measure," Gk. metra "lot, portion," L. metri "to measure." In Mod.Pers. this stem is extant in peymaân, peymaâné, âzmun, âzmâyeš.

An → affix made up of two separate parts which surround and attach to a base.

→ circum-; → affix.

The interface between a galaxy and the → intergalactic medium. The circumgalactic medium comprises gas located in the → halo of a galaxy extending out to the → virial radius.

→ circum-; → galactic.

Surrounding or revolving around the Moon.

Circumlunar, from → circum- + → lunar.

Situated around a → nucleus, as of a → circumnuclear disk.

→ circum- + → nuclear.

A thick disk of gas and dust clouds surrounding the → Galactic Center up to about 20 → light-years. The disk is very clumpy; the → clumps have densities of several 10⁵ particles/cm³, radii of about 0.3 light-years, and gas temperatures above 100 K. The hydrogen mass of the disk is a few 10⁴ → solar masses. Such circumnuclear disks are present also in other galaxies.

→ circumnuclear; → disk.

Situated around or near a pole, as of the Earth or the sky. → circumpolar star.

→ circum-; → polar.

Star that, from a given observer's → latitude, does not rise or set, but circles around the → celestial pole. To be circumpolar, a star must have a polar distance that is less than the observer's latitude. Whether a given star is circumpolar at the observer's latitude (φ) may be calculated in terms of the star's → declination (δ). The star is circumpolar if φ + δ ≥ +90° (observer in northern hemisphere), or φ + δ ≤ -90° (observer in southern hemisphere).

→ circumpolar; → star.

To draw a line around; encircle.

L. circumscribere "to draw a line around, confine," from → circum- + scribere "write," from PIE *skreibh-, from *sker- "to cut, incise."

Pirâkašidan, from pirâ-, → circum- + vešidan "to write," → inscribe.