An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 13009 Search : far
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-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-نو-اختری   
gâme-ye 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.

precession of the ecliptic
  پیشایان ِ هورپه   
pišâyân-e hurpeh

Fr.: précession de l'écliptique   

The component of general precession caused by the gravitational attraction of the planets on the Earth's center of mass. It causes the equinox to move eastward by about 0''.12 per year in the opposite direction to the → precession of the equator. This terminology replaces → planetary precession, according to an IAU resolution adopted in August 2006.

precession; → ecliptic.

precession of the equator
  پیشایان ِ هموگار   
pišâyân-e hamugâr

Fr.: précession de l'équateur   

That component of general precession caused by the combined effect of the Moon, the Sun and the planets on the equatorial protuberance of the Earth, producing a westward motion of the equinoxes along the ecliptic about 50'' per year. According to an IAU resolution adopted in August 2006, the present terminology replaces lunisolar precession.

precession; → equator.

<< < -es -iv -ti 21- a p abe abs abs acc acc acc act act ada adi ads aes Age Alb Alf ali all alp alt ama amp ana ang ang ann ano ant ant ape apo app app arb are ari art ass ast ast ast Atl ato ato Aug aut awa azi bac bal Bar Bar Bay bea Bep Bet BIC bij bin bio bir bla bla blu blu bol Boo bou Bq bre bri bub B[e cal cal can car car Cas cat cau cel cen Cer cha cha cha che chi CI cir cir cla cle clo clu co- cob coh col col col com com com com com com com com Com con con con con con con con con con con con con coo cor cor cor cos cos cos cou cov cra cri cro cry cum cur cyc d'A dar dat DC dea dec dec dec def def deh Del den dep des det deu dia dif dif dif dim dip Dir dis dis dis dis dis div dom dos dou dri Dum dus dyn dyn ear eas ecl Edd eff Ein eje ele ele ele ele eli emb emi Enc ene ens eph epo equ equ eru eth Eul eve evo exc exc exi exo exp exp ext ext Fab fai Fan fea fem fer fie fil fir fir fla flo flu foc For for fos fra fre fre fro fun g m Gal gal gal gas gau gel gen geo geo geo gho gla gno gra gra gra gra Gre Gre gro gyr had hal har Har HD hea hel hel Her Her Hic hig hip hol hor hos hov Hub hun hyd hyd Hyd hyp IC ide ill ima imp imp inc inc ind ind inf inf inf inf inj ins ins int int int int int int int int inv inv ion iro Isl iso iso Jac jet jud jur kel Kep kil Kle Kui Lag lam Lap Lar lat law lea len lep Lib lig lim lin lin Lio lit loc LOF lon Lor low lum lun Lup Lyo mac mag mag mag mag mag mai man Mar mas mas mat Max mea mec Mei Mer Mer met met Met mic mid Mil min Mir mix mod mod mol mon Mor mou mul muo mys nan nat nav nec Nep neu New New NGC nob nom non non nor not nuc nuc num Nyq obj obs obs oce oen OH omn opa ope opt opt opt orb ord Ori ort osc out ove oxi pai pan par par par par pas pea pen per per per per Per pet pha Pho pho pho pho Pic Pis Pla pla pla pla Ple poa pol pol pol pol pop pos pos pow pra pre pre pre pri pri pri pro pro pro pro pro pro pro Pto pul puz qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel rep res res res res ret Rhe rid rig ris Roe Ros rot rub rut Sag sam sat sca sca Sch sci sea sec sec see sel sem sen ser Sgr sha shi sho sid sig sim sin Sir ske sli smo soc sol sol sol sol sol sou sou spa spe spe spe spe sph spi spl spu sta sta sta sta sta ste ste sti sto str Str sub sub sub sul sup sup sup sup sur sus sym syn sys Tam Tay tel ten Ter Tha the the the thi thr tib tid tim tok Tor tot tra tra tra tra Tri tri tro tru tur twi Typ ufo ult unc uni uni uni upl ura uti val var vec vel ver ver vil vir vis voc von wak Was wav wax wea wei whi Wie win WN6 wom X-r yea You zer zod > >>