optically violent variable (OVV) quasar
kuâsâr-e vartande-ye nurâné surâ
Fr.: quasar variable optiquement violent
A member of a small subset of quasars consisting of bright radio galaxies whose flux of visible light output can vary by as much as 50% in a single day.
A silvery white metal which belongs to the → platinum group elements, symbol Pd. → Atomic weight 106.4, → atomic number 46, → melting point 1554.9 Â°C, → boiling point 2963 Â°C. It is used in alloys and as a catalyst.
Named 1803 by discoverer William Hyde Wollaston (1766-1828), after the asteroid → Pallas, which was discovered at about the same time.
Named after the German naturalist Peter Pallas (1741-1811), who first studied such a type of meteorites.
Of or pertaining to a parallax.
Adj. form of → parallax.
Fr.: angle parallactique
Of an object in the sky, the angle between the → celestial pole, the object, and the → zenith. Since parallactic angle describes the orientation on the sky of the object for a particular observer, it can be an important quantity in some observations.
Fr.: ellipse de parallaxe
The path on the sky of the apparent position of a star as seen from the Earth, due to the Earth's annual motion around the Sun.
Fr.: inégalité parallactique
An irregularity in the Moon's motion caused by the Sun's gravitational attraction, which sets the Moon ahead or behind its normal orbital position. The Moon is about 2 arcminutes ahead of its expected position at first quarter, and a similar amount behind at last quarter.
Fr.: mouvement parallactique
The proper motion of a star due to the effect of the Sun's motion relative to the → local standard of rest.
Didgašt, literally "view change," from did "sight, view; eye," from didan "to see" (Mid.Pers. ditan "to see, regard, catch sight of, contemplate, experience;" 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") + gašt "change, alteration," past stem of gaštan, gardidan "to turn, to change" (Mid.Pers. vartitan; Av. varət- "to turn, revolve;" Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend").
Fr.: angle de parallaxe
The angular displacement associated with → parallax.
1) Said of two or more things, such as lines or planes, that are equally
distant from one another at all points.
Parâsu, from parâ-, → para-, + su "direction, side," from Mid.Pers. sÃ´k "direction, side."
parallel axis theorem
farbin-e âsehâ-ye parâsu
Fr.: théorème des axes parallèles
The → moment of inertia of a body about any given axis is the moment of inertia about a parallel axis through the center of mass, plus the moment of inertia about the given axis if the mass were located at the center of mass. same as → Steiner's theorem.
parallel of altitude
A small circle on the celestial sphere whose plane is parallel to the celestial horizon. Same as → almucantar.
A solid figure whose six bases are → parallelograms, opposite pairs being identical and parallel.
periodically variable supergiant (PVSG)
abarqul-e vartande-ye dowreyi
Fr.: supergÃ©ante variable pÃ©riodiquement
A variable → supergiant star with typical periods of the order of 10 to 100 days and amplitudes less than a few tenths of a magnitude. PVSGs are thought to be pulsating → g modes, caused by a density inversion, arising from an → opacity bump, most likely from Fe, H, and/or He.
Fr.: parallaxe photométrique
havâsepehr-e parâsu-taxthâ, javv-e ~
Fr.: atmosphère plan-parallèle
An approximation used in many stellar atmosphere models that depict the atmosphere as being only one-dimensional and bounded at the top and bottom by horizontal plane surfaces normal to the direction of gravity.
Fr.: lame plan-parallèle
A piece of glass with plane parallel surfaces used to admit light into an optical system and to exclude dirt and moisture.
With a possibility of becoming actual; possibly.