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

The proper motion of a star due to the effect of the Sun's motion relative to the → local standard of rest.

→ parallactic; → motion.

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").

The angular displacement associated with → parallax.

→ parallax; → angle.

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."

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.

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

→ parallel; → altitude.

→ almucantar.

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.

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.

A paramagnetic substance, which possesses → paramagnetism.

→ para- + → magnet.

Relative to or characterized by → paramagnetism.

→ para- + → magnetic

The property of a substance that possesses a → magnetic permeability greater than that of a vacuum but significantly less than that exhibited by → ferromagnetism. In the absence of an external magnetic field the atomic → magnetic moments of the substance are randomly oriented and thus cancel each other out with no net total magnetic moment. Moreover the coupling between neighboring moments is weak. However, when a magnetic field is applied magnetic moments align with the direction of the field and so the magnetic moments add together. Therefore paramagnetic substances affect external fields in a positive way, by attraction to the field resulting in a local increase in the magnetic field. The → magnetization vanishes when the field is removed.

→ para- + → magnetism

General: Any of a set of physical properties whose values determine the characteristics or behavior of something. → impact parameter; → ionization parameter.
Math.: A constant or variable term in a function that determines the specific form of the function but not its general nature, as a in f(x) = kx, where k determines only the slope of the line described by f(x).

Mod.L. parametrum, from Gk. → para- + metron "measure," → meter.

Parâmun, from parâ-, → para-, + mun/mân "measure," as in Pers. terms pirâmun "perimeter," âzmun "test, trial," peymân "measuring, agreement," peymâné "a measure; a cup, bowl," from O.Pers./Av. mā(y)- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum; PIE base *me- "to measure."

Any of a set of equations that defines the coordinates of the dependent variables of a curve or surface in terms of one or more independent variables or parameters.

→ parametric; → equation.

An → ESO observatory, located on Cerro Paranal in the Atacama Desert, northern Chile, at 2,635 m altitude. It is about 120 km south of the town of Antofagasta and 12 km inland from the Pacific Coast. The Paranal Observatory hosts the → Very Large Telescope (VLT) with four 8.2 m telescopes. Each telescope provides one → Cassegrain and two → Nasmyth focus stations for facility instruments. One Nasmyth focus is available for visitor instruments. In addition each telescope is equipped with a → coudé focus station from which the light can be coherently combined in the interferometric focus. ESO also operates four 1.8 m Auxiliary Telescopes (ATs), that are used as an interferometric array (VISA) and a 4 m infrared survey telescope (VISTA). Currently, more than 10 instruments including two interferometric instruments (MIDI, AMBER) are operational and offered for science observations.

Paranal, the name of the mountain, in the Quechua language meaning "whirlwind;" → observatory.

An astronomical and meteorological calendar written by ancient Greeks from 450 B.C. during at least three centuries. The parapegma was an inscribed stone for public use. It had holes beside the inscription, in which a peg could be inserted next to the appropriate day. The term was later applied to purely written forms of such calendars, or almanacs; plural form parapegmata.

From → para- "next to" + pegma "something that fastens something else together," from pegnyein "to stick."

Characteristic of optical analyses that are limited to infinitesimally small apertures. Also called first-order or Gaussian optics.

→ para-; → axial.

From par(â)-, → para-, + âseyi→ axial.

A ray that lies close to and almost parallel to the optical axis and behaves according to paraxial equations.

→ paraxial, → ray.

A catalog of stars in the → Orion Nebula created by P. P. Parenago in 1954 (Publ. Astr. Inst. Sternberg, Band 25, p. 393-437, Moskau).

Pavel Petrovich Parenago (1906-1960), a Soviet astronomer.

1) General: A father or a mother. A precursor, or → progenitor.
2) Physics: A → nuclide that upon → radioactive decay or → disintegration yields a specific nuclide (the → daughter). See also → parent cloud, → parent element, → parent galaxy, → parent molecule.

From O.Fr. parent, from L. parentem (nominative parens) "father or mother, ancestor," from parere "to bring forth, give birth to, produce," from PIE base *per- "to bring forth"

Permâr, literally "father-mother" (as in Sogd. māt-pitri "parent"), from Gilaki per, → father, + Gilaki mâr, → mother.

Usually of a newborn star, the molecular cloud in which the star has formed.

→ parent; → cloud.