An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1001

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.


Fr.: provocation   

1) The act of provoking.
2) Something that → incites, → instigates, angers, or irritates (

Verbal noun of → provoke.


Fr.: provoquer   

1) To anger, enrage, exasperate, or vex.
2) To stir up, arouse, or call forth (feelings, desires, or activity).
3) To → incite or → stimulate (a person, animal, etc.) to action (

M.E., from O.Fr. provoker, provochier and directly from L. provocare "call forth, challenge," from → pro- "forth" + vocare "to call," → voice.

Farâvacidan, from farâ-, → pro-, + vacidan "to call," rarr; convoke.


Fr.: proue   

The forepart of a ship or boat; bow; opposite to stern or poopPuppis.

From M.Fr. proue, from Upper It. (Genoese) prua, from L. prora "prow," from Gk. proira, related to pro "before, forward," → pro-.

Farâl, from farâ "forward" (farâ raftan "to go forward, proceed," farâ rândan "to drive forward"), equivalent to → pro-, + relation suffix -âl, → -al. Compare farâl with prow "bow," Fr. la proue "prow, bow," from dialectal It. proa, prua, from L. prora "bow," from Gk. proira, related to pro "before, forward."

Proxima b
  پروکسیما b   
Proksimâ b

Fr.: Proxima b   

An → extrasolar planet orbiting our nearest stellar neighbor → Proxima Centauri. The planet was detected through a long-term → radial velocity campaign and found to have an → orbital period of ~ 11.2 days, a → semi-major axis of ~ 0.05 → astronomical units (20 times closer to Proxima than the Earth is to the Sun), and a minimum mass 1.3 → Earth masses (M sin i = 1.3 M_Earth), i.e. ~ 30% larger than the Earth (Anglada-Escudé et al. 2016, Nature 536, 437). The planet's surface temperature should allow it to support liquid water, and its mass suggests that it might have a rocky surface. With a semi-major axis of ~ 0.05 AU, it lies in the center of the classical habitable zone for Proxima. However, Proxima Centauri is a → flare star and the → X-ray flux received by the planet is 400 times greater than the flux that Earth receives from the Sun. Energetic particles associated with the flares may erode the atmosphere or hinder the development of primitive forms of life. It is also not known whether the → exoplanet has a magnetic field, like Earth, which could shield it from the dangerous stellar radiation.

Proxima Centauri.

Proxima Centauri
  پروکسیما کنتاؤروس، نزدیکترین ~   
proksimâ Kentâwros, nazdiktarin ~

Fr.: Proxima du Centaure   

The closest star to the Sun, lying 4.24 → light-years away. Other designations: α Centauri C, GL 551, HIP 70890, or simply Proxima. It is the faintest of the three stars that make up the → Alpha Centauri system. Proxima Centauri is a → red dwarf of → spectral type M6 Ve. It has a magnitude of +11.0, but undergoes sudden brightness increases of up to 1 mag lasting several minutes. Proxima is a late-type → flare star with a rotation period of ~ 84 days. Its mass is about 0.123 → solar masses or 129 → Jupiter masses. Proxima orbits the binary system AB at a distance of about 15,000 → astronomical unit (AU)s, with a period of approximately 550,000 years (Kervella et al., 2016, arXiv:1611.0349). In about 200,000 years it will be at the same distance as AB and in 240,000 years it will be farther to Sun than AB. It has an → effective temperature of only around 3,050 K, a luminosity of 0.15 per cent of that of the Sun, a measured radius of 14 per cent of the radius of the Sun and a mass of about 12 per cent of the mass of the Sun. An → exoplanet, named → Proxima b, has been discovered orbiting our nearest neighbor star. Proxima experiences a seven-year activity cycle, similar to the Sun's 11-year cycle (B. J. Wargelin, B. J. et al., 2016, arXiv:1610.03447). But unlike the Sun's relatively moderate flares, Proxima's outbursts of X-ray and ultraviolet radiation could prove deadly for any hypothetical life on its planet, Proxima b.

Proxima, feminine of proximus "nearest," superlative of prope "near;" → approximate; → Centaurus.

Proksimâ, from L., as above; Kentâwros, → Centaurus; nazdiktarin, superlative of nazdik "near," from Mid.Pers. nazdik "near," from nazd "close" (Mid.Pers. nazd, nazdik "near," nazdist "first;" O.Pers. ašna- "close;" Av. nazdišta- "nearest, next," nazdyo "nearer to," nas- "to come near, approach, reach;" cf. Skt. nédīyas- "closer, very close," nas- "to approach, to reach") + -ik, → -ic.

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