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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 1076
pragmatics
  ورزال‌گراییک   
varzâl-gerâyik

Fr.: pragmatique   

A branch of → semiotics dealing with the relation between language and the users, especially the constraints they encounter in using language in social interaction, and the corresponding effects on other users in the communication.

pragmatic; → -ics.

pragmatism
  ورزال‌گرایی   
varzâl-gerâyi

Fr.: pragmatisme   

Philo.: The doctrine that the truth or value of a concept or assertion is determined by its practical effects upon human interests.

pragmatic; → -ism.

Prandtl number
  عدد ِ پرانتل   
adad-e Prandtl

Fr.: nombre de Prandtl   

A dimensionless number representing the ratio of the fluid viscosity to the thermal conductivity of a substance; a low number indicates high convection.

Named after the German physicist Ludwig Prandtl (1875-1953); → number.

praxis
  ورزیدار   
varzidâr

Fr.: praxis   

1) The practice and practical side of knowledge or skills, as opposed to the → theory.
2) Accepted practice or custom.

M.L. praxis "practice, action," from Gk. praxis "practice, action, doing," from stem of prassein "to do, to act."

Varzidâr, from varzid past stem of varzidan, → practice, + -âr prefix forming nouns of action, such as kerdâr, raftâr, didâr, goftâr, jostâr, etc.

pre-
     
piš- (#)

Fr.: pré-   

A prefix meaning "before, prior to, in advance of, early, beforehand, in front of."

M.E., from O.Fr. pré-, from L. præ (adverb) "before."

Piš- "before; in front," from Mid.Pers. pêš "before, earlier," O.Pers. paišiya "before; in the presence of."

pre-cluster core
  مغزه‌ی ِ پیش-خوشه‌ای   
maqze-ye piš-xuše-yi

Fr.: cœur pré-amas   

A precursor of a small, loosely bound → star cluster (→ bound cluster) as well as an → OB association, with masses ranging from about 10 to 1000 → solar masses or more.

pre-; → cluster; → core.

pre-degenerate star
  ستاره‌ی ِ پیش-واگن   
setâre-ye piš-vâgen

Fr.: étoile pré-dégénérée   

Same as → PG 1159 star.

post-; → degenerate; → star.

pre-dispersion
  پیش-پاشش   
piš-pâšeš

Fr.: pré-dispersion   

A technique in spectroscopy which uses a combination of several dispersive elements (prisms in series or a grism) before focusing the light on the primary disperser, usually a grating, in order to achieve high spectral resolutions.

pre-; → dispersion.

pre-main sequence binary
  درین ِ پیش-رشته‌ی ِ فریست   
dorin-e piš-rešte-ye farist

Fr.: binaire pré-séquence principale Markarian's Chain   

A → binary system whose components are → pre-main sequence stars.

pre-; → main sequence; → binary.

pre-main sequence B[e] star (HAeB[e])
  ستاره‌یِ B[e]ی ِ پیش-رشته-ی فریست   
setâre-ye B[e]-ye piš-rešte-ye farist

Fr.: étoile B[e] pré-séquence principale   

A → Herbig AeBe star displaying → forbidden emission lines in its spectrum.

pre-; → main; → sequence; → B[e] star.

pre-main sequence star
  ستاره‌ی ِ پیش-رشته‌ی ِ فریست   
setâre-ye piš-rešte-ye farist

Fr.: étoile pré-séquence principale   

A star that evolves in the → Hayashi phase and has not yet reached the → zero-age main sequence.

pre-; → main sequence, → star.

pre-nova stage
  گامه‌ی ِ پیش-نووایی، ~ پیش-نو-اختری   
gâme-ye piš-novâ-yi, ~ piš-now-axtari

Fr.: étape pré-nova   

The stage of a star before its eruption to become a nova.

pre-; → nova; → stage.

pre-stellar
  پیش-ستاره‌ای   
piš-setâreyi

Fr.: pré-stellaire   

An adjective relating to a stage before the formation of a → protostar. → pre-stellar core.

pre-; → stellar.

pre-stellar core
  مغزه‌ی ِ پیش-ستاره‌ای   
maqze-ye piš-setâreyi

Fr.: cœur pré-stellaire   

A small, gravitationally unstable molecular → clump of typical size of less than 0.1 pc resulting from → gravitational collapse and → fragmentation of a larger → molecular cloud. It is a centrally concentrated structure which evolves into a → class 0 object, where eventually a single star or a stellar system is formed. Core masses range between 0.5 and 5 solar masses, with a mean number density of at least 104-105 cm-3, and a temperature as low as about 10 K. A pre-stellar core evolves into a → Class 0 object. Also called dense core.

pre-stellar; → core.

pre-WD star
  ستاره‌ی ِ پیش-کوتوله‌ی ِ سفید   
setâre-ye piš-kutule-ye sefid

Fr.: étoile pré-naine blanche   

A → post-planetary nebula star that is approaching the top of the → white dwarf sequence. These stars have exhausted the capacity of → nuclear burning in their cores.

pre-; → white; → dwarf.

prebiotic
  پیشزیستی   
pišzisti

Fr.: prébiotique   

Existing before or making possible the appearance of living organisms. Prebiotic molecules are biologically essential components such as amino acids, sugars, and nucleic-acid bases which are precursors of the origin of life.

pre- + → bio- + -tic equivalent of → -ic.

precess
  پیشایانیدن   
pišâyânidan

Fr.: précesser   

1) To correct celestial coordinates for → precession.
2) To undergo → precession.

Back formation from → precession.

Back formation from pišâyân, → precession.

precessed coordinates
  هم‌آراهای ِ پیشایانیده   
hamârâhâ-ye pišâyânidé

Fr.: coordonnées précessées, ~ corrigées de la précession   

The apparent position of a celestial object corrected for the epoch → precession.

Precessed, p.p. of → precess; → coordinates.

precession
  پیشایان   
pišâyân

Fr.: précession   

The periodic motion of the → rotation axis of a body such as a → spinning top in which the axis of rotation gradually sweeps out a conical shape. In the case of the spinning Earth, it is due to the combined → gravitational attractions of the → Sun, the → Moon, and → planets on Earth's → equatorial bulge. Since the Earth's axis is tilted to its → orbital plane or → ecliptic, the gravitational force of the Sun and the Moon on the Earth's equatorial bulge tend to pull it back toward the plane of ecliptic. As a result, the axis → precesses. Earth's axis of rotation precesses with a period of about 25,770 years, describing one complete circle on the → celestial sphere (→ precession constant). This circle has a radius of approximately 23°.5, equal to the → inclination of the Earth's orbit. Since the → vernal equinox is the reference direction for the → equatorial coordinate system, the coordinates of "fixed" objects change with time and must therefore be referred to an → epoch at which they are correct. → sign of zodiac.
See also → general precession; → precession of the ecliptic; → precession of the equator; → precession of the equinoxes; → precessional circle; → precession time; → geodetic precession; → general precession in longitude; → general precession in right ascension; → orbital precession; → perihelion precession; → planetary precession; → precession period.

L.L. præcissionem "a coming before," from L. præcessus, p.p. of præcedere "to happen before," from the fact that the equinoxes occur earlier each year with respect to the preceding year, from præ- "before," → pre-, + cedere "to walk, to go, to happen."

Pišâyân, literally "coming before," from piš- "before" → pre- + ây- (present stem of âmadan "to come, arrive, become"), from Av. ay- "to go, to come," aēiti "goes;" O.Pers. aitiy "goes;" Skt. e- "to come near," eti "arrival;" L. ire "to go;" Goth. iddja "went," Lith. eiti "to go;" Rus. idti "to go;" + -ân suffix of space and time.

precession constant
  پایای ِ پیشایان   
pâyâ-ye pišâyân

Fr.: constante de précession   

The amount by which the equinoctial points drift westward annually due to precession. Its value for epoch J2000.0 is 50''.26, resulting from the westward → precession of the equator (50".38), and the eastward → precession of the ecliptic (0".12).

precession; → constant.

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