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: 13003 Search : far
presolar grain
  دانه‌ی ِ پیش-خورشیدی   
dâne-ye piš-xoršidi

Fr.: grain pré-solaire   

A → refractory → nanoparticle embedded in → meteorites and → interplanetary dust particles whose → isotopic ratios suggest formation earlier than the Solar System.

presolar; → grain.

Press-Schechter formalism
  دیسه‌گرایی ِ پرس-ششتر   
disegerâyi-ye Press-Schechter

Fr.: formalisme de Press-Schechter   

A mathematical analysis, based on → self-similarity, used to predict the → mass function of spherically collapsing → dark matter halos. The formalism assumes that the fraction of mass in halos more massive than M is related to the fraction of the volume in which the smoothed initial density field is above some threshold δcρ, where ρ is the average density of the Universe, with the volume encompassing a mass larger than M. A variety of smoothing → window functions and thresholds have been argued, but the most common is a top-hat window in real space and δc≅ 1.69. The Press-Schechter formalism provides a relatively good fit to the results of numerical simulations in cold dark matter theories.

First described by William H. Press and Paul Schechter's paper (1974, ApJ 187, 425); → formalism.

pressure
  فشار   
fešâr (#)

Fr.: pression   

The force per unit area.

M.E., from O.Fr. pressure, from L. pressura "action of pressing," from pressus, p.p. of premere "to press, compress."

Fešâr "squeezing, constriction, compression," verb fešordan, fešârdan "to press, squeeze;" phonetic variants Lori xošâr, Aftari xešâr, Qazvini, Qomi xošâl; cf. Khotanese ssarr- "to exhilarate;" loaned in Arm. ôšarak, in Ar. afšaraj "juice."

pressure broadening
  پهنش ِفشاری   
pahneš-e fešâri

Fr.: élargissement par pression   

A broadening of spectral lines caused mainly by the stellar atmospheric density and the surface gravity of the star. The line strength of a spectral line depends on the number of atoms in the star's atmosphere capable of absorbing the wavelength in question. For a given temperature, the more atoms there are, the stronger and broader the spectral line appears. Denser stars with higher surface gravity will exhibit greater pressure broadening of spectral lines.

pressure; → broadening.

pressure gradient
  زینه‌ی ِ فشار   
zine-ye fešâr

Fr.: gradient de pression   

The pressure difference between two adjacent regions of a fluid that results in a force being exerted from the high pressure region toward the low pressure region.

pressure; → gradient.

pressure gradient force
  نیروی ِ زینه‌ی ِ فشار   
niru-ye zine-ye fešâr

Fr.: force du gradient de pression   

A force resulting from → pressure gradient that is directed from high to low pressure.

pressure; → gradient; → force.

pressure ionization
  یونش ِ فشاری   
yoneš-e fešâri

Fr.: ionisation par pression   

A physical state of dense matter in which the electrostatic field of one atom should influence a neighboring atom and hence disturb atomic levels. In extreme case, such as white dwarfs, electron clouds practically rub and electrons are ionized off the parent atoms.

pressure; → ionization.

pressure mode
  ترز ِ فشار، مد ِ ~   
tarz-e fešâr, mod-e ~

Fr.: mode pression   

Same as → p mode

pressure; → mode.

pressure scale height
  بلندی ِ مرپل ِ فشار   
bolandi-ye marpel-e fešâr

Fr.: hauteur d'échelle de pression   

A basic ingredient of the → mixing length theory that scales with the → mixing length. It is defined by the relation: HP = -dr/dln P = -Pdr/dP , where r is the height and P the pressure. See also → scale height.

pressure; → scale; → height.

previous
  پیشین   
pišin (#)

Fr.: précédent   

Occurring before something else in time or order.

From L. praevius "leading the way," from prae-, → pre- + via "way."

Pišin, from piš "before," → pre-.

previously
  پیشانه   
pišâné

Fr.: précédemment, auparavant   

Coming or occurring before something else; prior.

previous; → -ly.

Prevost's law of exchanges
  قانون ِ گهولش ِ په‌ره‌وُ   
qânun-e gahuleš-e Prévost

Fr.: loi des échanges de Prévost   

A statement concerned with thermodynamic heat exchange, according to which bodies in → thermal equilibrium are simultaneously absorbing and emitting radiant energy. A body radiates in the same way whether other bodies are present or not. Also called Prevost's theory of exchanges.

Named after Pierre Prévost (1751-1839), a Swiss philosopher and physicist, who, in 1791, put forward the statement; → law; → exchange.

prey
  ۱) چَویدن؛ ۲) چَواک   
1) cavidan; 2) cavâk

Fr.: 1) faire sa proie de; 2) proie   

1) To seize and devour prey, as an animal does.
2) An animal hunted or seized for food, especially by a carnivorous animal (Dictionary.com).

M.E. preye, from O.Fr. preie, from L. praeda "booty, plunder, game hunted;" ultimately from prehendere "to grasp, seize."

1) Cavidan, related to Khotanese cev- "to get, seize," Ossetic cævyn, cavd "to hit, to strike," Pers. câpidan "to plunder," cafsidan, caspidan "to stick; to plunder;" Proto-Ir. *cap- "to seize."
2) Cavâk, from cav- present stem of cavidan, as above, + -âk suffix denoting object of an action.

prey animal
  جانور ِ چَواک   
jânevar-e cavâk

Fr.: animal proie   

An animal that is hunted and killed by a → predator as food.

prey; → animal.

Priestley's rings
  حلقه‌های ِ پریستلی   
halqehâ-ye Priestley

Fr.: anneaux de Priestley   

The concentric colored rings formed by an electrical → spark when a → discharge takes place on a metallic plate.

Joseph Priestley (1733-1804), English chemist, author, and clergyman; → ring.

primary
  نخستان   
naxostân

Fr.: primaire, principal   

1) First or highest in rank or importance; chief; principal.
2) Abbreviation for → primary body, → primary star, or → primary mirror.

M.E., from L. primarius "of the first rank, principal," from primus "first."

Naxostân, from naxost, from Mid.Pers. naxust "the first," Parthian Mid.Pers. nxwšt, from naxu, Manichean Parthian nwx "beginning" + -ist superlative suffix, Av. -išta-, cf. Skt. -istha-, Gk. -istos, O.H.G. -isto, -osto, O.E. -st, -est, -ost.

primary body
  جسم ِ نخستان   
jesm-e naxostân

Fr.: corps principal   

The body that is being orbited; such as the → Sun in the → solar system. As regards → multiple star systems, the most massive, or → primary star. See also: → secondary body.

primary; → body.

primary cell
  پیل ِ نخستان   
pil-e noxostân

Fr.:   

A → cell in which the electrochemical action producing the current is not normally reversible. Such a cell cannot be recharged by an electric current. → secondary cell.

primary; → cell.

primary cosmic rays
  پرتوهای ِ کیهانی ِ نخستان   
partowhâ-ye keyhâni-ye naxostân

Fr.: rayons cosmiques primaires   

The → cosmic rays which arrive on the Earth's → atmosphere from the outer space. The primary cosmic rays are very high energy → protons and to a lesser extent heavier nuclei which rain upon the Earth from all diretions in the outer space. They contain about 90% protons, 7% → alpha particles and about 1% still heavier nuclei of amost all the atoms from Li to Ni ( → mass number< 60). See also: → secondary cosmic rays.

primary; → cosmic; → ray.

primary eclipse
  گرفت ِ نخستان   
gereft-e noxostân

Fr.: éclipse primaire   

Of a transiting → exoplanet, the event and the interval of time during which the planet passes in front of its host star. The planet occults a portion of the stellar disk, and a fraction of light from the star is seen after traversal through the atmosphere around the planet's limb. → secondary eclipse.

primary; → eclipse.

<< < -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 Io ion iro isl iso iso Jal JHK Jul jur Kel Kep kin kne L2 Lag lam Lap lar lat law Lec len Lep lib lig lin lin lin liq lit loc log lon los low lum lun lux Lyr mac mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mom moo mor mov mul mur Na nar nat nea neg Nes neu New New Nic nod non non non Nor nov nuc nul num OB obl obs occ Ock off Ohm on- ope opi opt opt orb orb ord Ori ort OSI out ove ozo pal pan par par par par pat pec pen per per per per per Pfu pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro Pro pub pul pyr qua qua qua qua qui rad rad rad rad rad rad rak ran rat Ray rea rec rec rec red ref ref reg reg rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set sha SHB sho sib sid sil sim sin sit sky slo Sne Soc sol sol sol sol son sou spa spa spe spe spe spe sph spi spo Squ sta sta sta sta ste ste ste sto str str str sub sub sub sum sup sup sup sup sur sus sym syn T d tap tec tem ten tes the the the the thi thr tid tim tip ton tor tow tra tra tra tra tri tri tru tub tur two Typ ult un- und uni uni uno upp urg UX Van var veg vel ver vib vio vir vis Voi vow wan wat wav WC wea wel whi Wil wir WNh wor X-r yel Z C zer ZZ > >>