An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 139 Search : all
optically violent variable (OVV) quasar
  کو‌آسارِ ورتنده‌ی ِ نورانه سورا   
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.

optically; → violent; → variable; → quasar.

pâlâdiom (#)

Fr.: palladium   

A silvery white metal which belongs to the → platinum group elements, symbol Pd. → Atomic weight 106.4, → atomic number 46, → melting point 1554.9 °C, → boiling point 2963 °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.


Fr.: pallasite   

A class of → iron meteorite containing → olivine crystals.

Named after the German naturalist Peter Pallas (1741-1811), who first studied such a type of meteorites.


Fr.: parallactique   

Of or pertaining to a parallax.

Adj. form of → parallax.

parallactic angle
  زاویه‌ی ِ دیدگشتی   
zâviye-ye didgašti

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.

parallactic; → angle.

parallactic ellipse
  بیضی ِ دیدگشت   
beyzi-ye didgašt

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.

parallactic; → ellipse.

parallactic inequality
  ناهموگی ِ دیدگشتی   
nâhamugi-ye didgašti

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.

parallactic; → inequality.

parallactic motion
  جنبش ِ دیدگشتی   
jonbeš-e didgašti

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.

parallactic; → motion.

didgašt (#)

Fr.: parallaxe   

The apparent → shift of a nearby object's → position in relation to more distant ones when the nearby object is observed from different → viewing angles. See also → stellar parallax.

From M.Fr. parallaxe, from Gk. parallaxis "change, alteration," from parallassein "to alter, make things alternate," from → para- "beside" + allassein "to change," from allos "other;" → alias.

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").

parallax angle
  زاویه‌ی ِ دیدگشت   
zâviye-ye didgašt

Fr.: angle de parallaxe   

The angular displacement associated with → parallax.

parallax; → angle.


Fr.: parallèle   

1) Said of two or more things, such as lines or planes, that are equally distant from one another at all points.
2) Electricity: An arrangement of the components in an electric circuit so that the same voltage is applied to each component. Compare → series.

From M.Fr. parallèle, from L. parallelus, from Gk. parallelos "parallel," from para allelois "beside one another," from → para- "beside" + allelois "each other," from allos "other," → alias.

Parâsu, from parâ-, → para-, + su "direction, side," from Mid.Pers. sôk "direction, side."

parallel axis theorem
  فربین ِ آسه‌ها‌ی ِ پراسو   
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; → axis; → theorem.

parallel of altitude
  پرهون ِ فرازا   
parhun-e farâzâ

Fr.: almucantar   

A small circle on the celestial sphere whose plane is parallel to the celestial horizon. Same as → almucantar.

parallel; → altitude.


  پراسورویه، لوزی‌وار   
parâsuruyé, lowzivâr

Fr.: parallélépipède   

A solid figure whose six bases are → parallelograms, opposite pairs being identical and parallel.

From Gk. parallelepipedon, from parallelos, → parallel + epipedon "plane surface," from neuter of epipedos "flat," from → epi- + pedon "ground," cognate with L. ped-, pes, → foot.

Parâsuruyé, from parâsu, → parallel, + ruyé, → surface. Lowzivâr, from lowzi, → rhombus + -vâr, → -oid.


Fr.: parallélogramme   

A four-sided → polygon whose opposite sides are parallel. A parallelogram all of whose angles are right angles is a → rectangle.

From Fr. parallélogramme, from L. parallelogrammum, from Gk. parallelogrammon "bounded by parallel lines," from parallelos, → parallel, + gramme "line," related to graphein "to write, draw" → -graph.

Parâsubar, from parâsu, → parallel, + bar, → side.

periodically variable supergiant (PVSG)
  ابرغول ِ ورتنده‌ی ِ دوره‌ای   
abarqul-e vartande-ye dowreyi

Fr.: supergéante variable périodiquement   

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.

periodical; → -ly; → variable; → supergiant.

photometric parallax
  دیدگشت ِ شیدسنجیک   
didgašt-e šidsanjik

Fr.: parallaxe photométrique   

A method of deriving the distance of a star using its → apparent magnitude and the → absolute magnitude inferred from its → spectral type.

This is a misnomer, because the method has nothing to do with parallax; → photometric; → parallax.

plane-parallel atmosphere
  هواسپهر ِ پراسو-تخت، جو ِ ~   
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.

plane; → parallel; → atmosphere.

plane-parallel plate
  تیغه‌ی ِ تخت-پراسو   
tiqe-ye taxt-parâsu

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.

plane; → parallel; → plate.


Fr.: potentiellement   

With a possibility of becoming actual; possibly.

potential; → -ly.

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