An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < -ph pal par par par par pas Pau pen per per per per Per per pha Pho pho pho pho Pia Pis Pla pla pla pla Ple Pog pol pol pol pol pop pos pot Poy pre pre pre pre pri pri pro pro pro pro pro pro pro pub pul pyr > >>

Number of Results: 1026
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.


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.


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.


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.


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.


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.


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.

  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.


Fr.: démontrable   

Capable of being demonstrated or proved.

prove; → -able.


Fr.: prouver   

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



Fr.: proverbe   

A short popular saying, usually of unknown and ancient origin, that expresses effectively some commonplace truth or useful thought (

pro-; → verb.

<< < -ph pal par par par par pas Pau pen per per per per Per per pha Pho pho pho pho Pia Pis Pla pla pla pla Ple Pog pol pol pol pol pop pos pot Poy pre pre pre pre pri pri pro pro pro pro pro pro pro pub pul pyr > >>