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: 12929 Search : far
proton
  پروتون   
proton (#)

Fr.: proton   

A particle of the hadron family which is one of the two particles that make up atomic nuclei. It has an electric charge of one positive fundamental unit, a diameter of about 1.65 x 10-13 cm, and a mass of about 1.67 x 10-24 g (about 938 MeV c-2).

From Gk. proton, neuter of protos "first." Coined by Eng. physicist Ernest Rutherford (1871-1937).

proton temperature
  دمای ِ پروتونی   
damâ-ye protoni

Fr.: température protonique   

The temperature in the → solar wind, as derived from the mean kinetic energy of protons: mv2/2 = (3/2)kTp, where k is → Boltzmann's constant. There are two types of proton temperature: parallel temperature, measured from protons moving parallel to the magnetic field, and perpendicular temperature relating to protons at right angles to the magnetic field. The proton temperature is usually derived using particle detectors on board space probes that determine the velocity → distribution function of the particles from their energies (N. Meyer-Vernet, 2007, Basics of the Solar Wind, Cambridge Univ. Press). See also → electron temperature.

proton; → temperature.

proton-proton chain
  زنجیره‌ی ِ پروتون-پروتون   
zanjire-ye proton-proton (#)

Fr.: chaîne proton-proton   

A series of → thermonuclear reactions, taking place mainly in → low-mass stars, such as the Sun, which transforms four hydrogen nuclei (protons) into one helium (4He) nucleus and thereby generates energy in the stellar core. First, two protons (1H) combine to form a → deuterium nucleus (2H) with the emission of a → positron (e+) and a → neutrino (ν): 1H + 1H → 2H + e+ + ν. The deuterium nucleus then rapidly captures another proton to form a helium-3 nucleus (3He), while emitting a → gamma ray (γ): 2H + 1H → 3He + γ. There are three alternatives for the next step. In the PP I chain, occurring in 86% of the cases, two 3He nuclei fuse to a final 4He nucleus while two protons are released: 3He + 3He → 4He + 1H + 1H. The mass of the resulting 4He nucleus is less than the total mass of the four original protons used to produce 4He (→ mass defect). The difference, ~ 0.7% of the total mass of the protons, is converted into energy and radiated by the Sun. In this process, the Sun loses some 4 million tons of its mass each second. See also → CNO cycle.

proton; → chain.

proton-proton reaction
  واژیرش ِ پروتون-پروتون   
vâžireš-e-e proton-proton

Fr.: réaction proton-proton   

A → thermonuclear reaction in which two protons collide at very high velocities and combine to form a → deuterium. See also → proton-proton chain.

proton; → reaction.

protoneutron star
  ستاره‌ی ِ پوروا-نوترونی   
setâre-ye purvâ-notroni

Fr.: proto-étoile à neutrons   

A compact, hot, and → neutrino-rich object that results from a → supernova explosion and is a transition between an → iron core and a → neutron star or → black hole. The life span of a protoneutron star is less than one minute.

proto-; → neutron; → star.

protoplanet
  پوروا-سیاره   
purvâ-sayyâré

Fr.: protoplanète   

A stage in the formation of a → planet, which comes about from the aggregation of → planetesimals. The protoplanet eventually becomes a planet by → accretion of material from a → protoplanetary disk.

proto- + → planet.

protoplanetary disk
  گرده‌ی ِ پوروا-سیاره‌ای   
gerde-ye purvâ-sayyâreyi

Fr.: disque protoplanétaire   

A → circumstellar disk of gas and dust surrounding a → pre-main sequence star from which planetary systems form. Protoplanetary disks are remnants of → accretion disks which bring forth stars. Typically, their sizes are ~100-500 AU, masses ~10-2 solar masses, lifetimes ~106-107 years, and accretion rates ~10-7-10-8 solar masses per year. According to the standard theory of planet formation, called core accretion, planets come into being by the growth of → dust grains which stick together and produce ever larger bodies, known as → planetesimals. The agglomeration of these planetesimals of 100 to 1000 km in size into rocky Earth-mass planets is the main outcome of this theory. Beyond the → snow line in the disk, if the masses of these cores of rock and ice grow higher than 10 times that of Earth in less than a few million years, gas can rapidly accrete and give rise to giant gaseous planets similar to → Jupiter. If core building goes on too slowly, the disk gas dissipates before the formation of → giant planets can start. Finally the left-over planetesimals that could not agglomerate into rocky planets or core of giant planets remain as a → debris disk around the central object that has become a → main sequence star. An alternative to core accretion theory is formation of planets in a massive protoplanetary disk by → gravitational instabilities. The validity of these two theories is presently debated. See also → protoplanet.

protoplanet; → disk.

protoplanetary nebula
  پیش-میغ ِ سیاره‌ای   
piš-miq-e sayyâre-yi

Fr.: pré-nebuleuse planétaire   

preplanetary nebula.

proto-; → planetary; → nebula.

protoplasm
  پوروا-پلسم   
purvâplasm

Fr.: protoplasme   

The fluid substance within the living cell that consists of two major divisions, the cytoplasm and the nucleoplasm (cell nucleus). It is composed mainly of nucleic acids, proteins, lipids, carbohydrates, and inorganic salts.

proto- + -plasm, → plasma.

protosolar
  پوروا-خورشیدی   
purvâ-xoršidi

Fr.: protosolaire   

Describing the conditions prior to the formation of the → solar system, or pertaining to the → protostar that became the → Sun.

proto- + → solar.

protosolar abundance
  فراوانی ِ پوروا-خورشیدی   
farâvâni-ye purvâ-xoršidi

Fr.: abondance protosolaire   

The abundance of a chemical element pertaining to the proto-→ solar nebula from which the → solar system was formed. → CI chondrite; → CAI meteorite.

protosolar; → abundance.

protostar
  پوروا-ستاره   
purvâ-setâré

Fr.: protoétoile   

A stage in the process of → star formation, after the → gravitational collapse of the dense → pre-stellar core and before the initiation of → nuclear fusion in the central object which will eventually become a star. Protostars are classified into four groups: → Class 0, → Class I, → Class II, and → Class III.

proto- + → star.

protostellar
  پوروا-ستاره‌ای   
purvâ-setâreyi

Fr.: protostellaire   

Of or pertaining to → protostars.

proto-; → stellar.

protostellar collapse
  ر ُمبش ِ پوروا-ستاره‌ای   
rombeš-e purvâ-setâreyi

Fr.: effondrement protostellaire   

A → gravitational collapse leading to the formation of a → protostar.

protostellar; → collapse.

protostellar disk
  گرده‌ی ِ پوروا-ستاره‌ای   
gerde-ye purvâ-setâreyi

Fr.: disque protostellaire   

A disk of gas and dust surrounding a → protostar. These structures are rotating → accretion disks through which matter is transferred to protostars.

protostellar; → disk.

protostellar jet
  شان ِ پورواستاره‌ای   
šân-e purvâsetâre-yi

Fr.: jet protostellaire   

A high-velocity and highly → collimated jet associated with the earliest phase of → star formation that propagating along the polar axis of the → protostar-→ accretion disk system. Protostellar jets are usually detected in the [S II], [O I], and Hα lines and are therefore referred to as optical jets. They may have more than a parsec in length. Their formation is related to the → magnetohydrodynamics (MHD) of accretion disks. These jets are detected in protostellar sources over a wide range of masses, from the very early stages of formation (sources associated with infalling envelopes whose mass exceeds that of the growing star) all the way to the → classical T Tauri stars, whose envelopes have already dispersed. This phenomenon is thought to play a key role in regulating the star formation process by removing the excess → angular momentum of disk material and enabling matter to flow toward the center. Protostellar winds also provide an important → feedback mechanism between the forming star and the surrounding medium, to which they return mass and energy. Protostellar jets are at the origin of → bipolar outflows. The et sweeps up ambient → molecular cloud material into two thin shells, which manifest themselves as the observed bipolar lobes of → carbon monoxide (CO) emission. Once the molecular cloud material has been swept away (on a timescale of 105 years), the bipolar outflow disappears, leaving the protostellar jet to erratically fire away for a further 106-107 years.

protostellar; → jet.

protosun
  پوروا-خورشید   
purvâ-xoršid

Fr.: proto-Soleil   

The Sun at its protostellar formation stage, before becoming a main sequence star, nearly 5 billion years ago. The protosun was more luminous than today and larger, with a radius comparable to that of the orbits of the inner planets

proto- + → sun.

prototype
  پوروا-گون، پوروا-گونه   
purvâ-gun, purvâ-guné

Fr.: prototype   

The original or model on which something is based or formed.
Something that serves to illustrate the typical qualities of a class.

proto-; → type.

provable
  آوینیدنی   
âvinidani

Fr.: démontrable   

Capable of being demonstrated or proved.

prove; → -able.

prove
  آوینیدن   
âvinidan

Fr.: prouver   

To supply proof of, to establish or demonstrate the truth or validity of.

proof.

<< < -es -iv -ti 217 a- abe abs abs acc acc ach act act ada adi adv aff agg Alc Alf ali all alp alt Ama amp ana ang ang ann ano ant ant ape apo app aps arc arg arm art ass ast ast ast atm ato att aur aut axi B-t bai Bal bar bar Be bee Bes bi- bif bin bin bio bis bla bli blu Boe Bol bor bou bra bri Bro bum CAI cal Can cap car car cat cat CCD Cel cen CGS cha cha che che chr cir cir civ cla clo clo CMB coa coe coh col col col Com com com com com com com com com 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 dev dia dif dif dif dim dip dir dis dis dis dis dis div dom dou dou dri dup dus dyn dyn ear eas ecl Edd eff Ein Ekm ele ele ele ele ell emb emi enc ene ent eph equ equ equ eru eth eup eve EX exc exe exi exo exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla flo flu fog for for Fou fra fre Fre Fro fus G-t gal gal Gam gas Gau Gem gen geo geo geo gia gla gol gra gra gra gra Gre Gre gui H a haf Hal har har He- hea hel Hel her Her hie hig his hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima imp imp imp inc ind ind ine 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 kly L d Lag lam Lap lar lat law Lea len lep lib lig lin lin lin liq lit loc log lon Los low lum lun Lut Lyr mac mag mag mag mag mag maj man Mar mas mas mat mea mec mem mer mes met met met mic mid mil min Mir Miz mod mol mon moo MOS mul mul mut nai nas nat neb neg Neu neu New New Nih noi non non non nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove oxi pac Pal par par Par par pas Pau Pel per per per per per per pha phi pho pho pho phy pip Pla pla pla pla pla Plu Poi pol pol pol pop pos pos pot 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 Ras Ray rea rec rec rec red red ref reg reg rel rel rel rep res res res res rev rhe Rie Rig Rit roe Ros rot Ruf Ryd Sag sam sat sca sca Sch Sco sec sec sec seg sel sem sen set sha SHB sho sib sie sil sim sin sit sky slo sno sod sol sol sol sol sor sou Spa spa spe spe spe sph spi Spi spr sta sta sta sta sta ste ste Ste sto str str sub sub sub suf sun sup sup sup sup sur swo syn sys tak Tay Tel ten ter tet the the the thi Tho thu tid tim toa top tot tra tra tra tra tri tri tro Tru tur twi Typ UBV ult unb uni uni uni up ura uti val var vec Vel ver ver vig vir vis VLT vol wad was wav wav wea wei Whe Wie win WN5 Wol X-r yea You zer zod > >>