An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 1001
planetary nebula
  میغ ِ سیاره‌ای   
miq-e sayyâreyi

Fr.: nébuleuse planétaire   

A hot envelope of gas ejected from a central evolved star before becoming a → white dwarf. At the end of the → asymptotic giant phase the pulsating → red giant star is surrounded by an extended shell formed by the material ejected from it. As the evolved star contracts, its → effective temperature rises considerably. When it reaches about 30,000 K, the radiated photons become energetic enough to ionize the atoms in the nebula. The nebula becomes then visible in the optical. It shines essentially in a few → emission lines, produced by cascades during recombination or by collisional excitation with electrons. The central stars of planetary nebulae, → CSPNe, are typically 0.6 to 0.8 solar masses. They have → main sequence masses in the range 1 to 8 solar masses, with an average mass of 2.2 solar masses for a standard → initial mass function. Thus a total of about 1.6 solar masses is in average lost during the → AGB and planetary nebula phases. The life-time of planetary nebulae is relatively short. A typical planetary nebula lasts only a few 10,000 years.

planetary; → nebula. The name comes from the fact that these objects appear as planetary disks in a low-resolution telescope. The first planetary nebula, designated NGC 7009 or the → Saturn Nebula, was discovered in 1782 by the German-born English astronomer William Herschel (1738-1822), who described it as "planetary nebula."

planetary physics
  فیزیک ِ سیارگان   
fizik-e sayyâregân (#)

Fr.: physique des planètes   

The study of the structure, composition, as well as physical and chemical properties of the planets of the solar system, including their atmospheres and their immediate cosmic environment.

planetary; → physics.

planetary precession
  پیشایان ِ سیاره‌ای   
pišâyân-e sayyâre-yi

Fr.: précession planétaire   

The motion of the → ecliptic plane caused by the gravitational influence of the other planets, mainly → Jupiter. The observational effect of planetary precession is similar to that of the → lunisolar precession. But planetary precession causes the → equinoxes to move along the ecliptic in the opposition direction (eastward) from that of luni-solar precession (westward) and at a much slower rate: 0''.12 per year. Same as → precession of ecliptic.

planetary; → precession.

planetary ring system
  راژمان ِ حلقه‌های ِ سیاره‌ای   
râžmân-e halqehâ-ye sayyâre-yi

Fr.: système d'anneaux planétaires   

Interplanetary dust and other small particles organized into thin, flat rings encircling a planet. The most spectacular planetary rings known are those around → Saturn, but the other three → giant planets of the solar system (→ Jupiter, → Uranus, and → Neptune) have their own ring systems.

planetary; → ring; → system.

planetary science
  سیاره‌شناسی   
sayyârešenâsi (#)

Fr.: planétologie   

The branch of astronomy that deals with the science of planets, or planetary systems, and the solar system.

planetary; → science.

planetary system
  راژمان ِ سیاره‌ای   
râžmân-e sayyâreyi

Fr.: système planétaire   

A system composed of a star and all the celestial bodies bound to it by gravity, especially planets and their natural satellites.

planetary; → system.

planetary transit
  گذر ِ سیاره‌ای   
gozar-e sayyâre-yi (#)

Fr.: transit planétaire   

The passage of an → inferior planet against the disk of the Sun, as viewed from Earth. Mercury and Venus pass in front of the Sun only when they are close to one of their → orbital nodes, at → inferior conjunction. For Mercury this occurs at the beginning of November (the → ascending node) or at the beginning of May (the → descending node), while for Venus it takes place at the beginning of December (the ascending node) or at the beginning of June (the descending node). See also → transit of Mercury, → transit of Venus.

planetary; → transit.

PLAnetary Transits and Oscillations of stars (PLATO)
  پلاتو   
PLATO

Fr.: PLATO   

A space observatory under development by the → European Space Agency for launch around 2024. Its objective is to detect and characterize → exoplanets by means of their → transit signature in front of a very large sample of → bright stars, and measure the seismic oscillations (→ asteroseismology) of the parent stars orbited by these planets in order to understand the properties of the exoplanetary systems.

planetary; → transit; → oscillation; → star.

planetesimal
  خرده‌سیاره   
xordesayyâré

Fr.: planétésimal   

Any of numerous small solid bodies in a → protoplanetary disk that in some cases clump together to form → planets but in other cases remain relatively small and become → asteroids and → comets. Similarly, → Kuiper Belt Objects are probably the remnants of the planetesimals that formed the planets.

From → planet + (infinit)esimal, → infinitesimal.

Xordesayyâré, from xordé "small, minute; crumbs," from xord "minute, little, small" (from Mid.Pers. xvart, xôrt "small, insignificant;" Av. ādra- "weak, dependent;" Skt. ādhrá- "small, weak, poor," nādh "to be oppressed;" Gk. nothros "sluggish;" PIE base *nhdhro-) + sayyâré, → planet.

planetoid
  سیارک   
sayyârak (#)

Fr.: planétoïde   

An older equivalent for → asteroid.

planet + → -oid.

planetology
  سیاره‌شناسی   
sayyârešenâsi (#)

Fr.: planétologie   

Same as → planetary science.

planet; + → -logy.

plani-
  تخت-   
taxt- (#)

Fr.: plani-   

Variant of → plano-, as in → planisphere.

plane.

planisphere
  تخت-سپهر، تخت-کره   
taxt-sepehr, taxt-koré

Fr.: planisphère   

A projection or representation of the whole or a part of a sphere on a plane. In particular, a polar projection of the celestial sphere or the Earth on a plane.

plani-; → sphere.

planispheric
  تخت-سپهری، تخت-کره‌ای   
taxt-sepehri, taxt-kore-yi

Fr.: planisphérique   

Of or relating to → planisphere.

planisphere + → -ic..

planispheric astrolabe
  اسطرلاب ِ تخت-سپهری، ~ کره‌ای   
ostorlâb-e taxt-sepehri, ~ kore-yi

Fr.: astrolabe planisphérique   

The most common form of the → astrolabe in which both the → celestial sphere and the observer's horizon are projected on to one or more plane surfaces by means of the stereographic projection. See also → universal astrolabe and → particular astrolabe.

planispheric; → astrolabe.

plano-
  تخت-   
taxt- (#)

Fr.: plano-   

A combining form meaning "flat, plane," used in the formation of compound terms. Also plani- and plan- before a vowel, → plane.

plane.

plano-concave lens
  عدسی ِ تخت-کاو   
adasi-ye taxt-kâv (#)

Fr.: lentille plano-concave   

A → divergent lens composed of one concave surface and one plane surface. This type of lens has a negative focal point and produces a → virtual image.

plano-; → concave; → lens.

plano-convex lens
  عدسی ِ تخت-کوژ   
adasi-ye taxt-kuž (#)

Fr.: lentille plano-convexe   

A → convergent lens that has one flat side and one convex side. Plano-convex lenses focus parallel rays of light to a positive point, thus forming → real images.

plano-; → convex; → lens.

plant
  گیاه   
giyâh (#)

Fr.: plante   

A living organism, in the Kingdom Plantae, with cellulose cell walls and lacking a nervous system or powers of voluntary motion.

M.E. plaunte; O.E. plante; L. planta "shoot, sprig, scion."

Giyâh "plant;" dialectal Bašâkardi gidâ(h), gida; Av. gaodāyu-, literally "cattle nourisher," from gao- "cattle, bull, ox," → Taurus, + dāyu- "nourisher," from dā(y)- "to feed" (Gershevitch 1962); Mod.Pers. dâyé "wet nurse;" cognate with L. femina "woman, female," → feminism; PIE base *dheh(i)- "to suck, suckle."

Plaskett's star
  ستاره‌ی ِ پلسکت   
setâre-ye Plaskett (#)

Fr.: étoile de Plaskett   

A → binary system consisting of two → massive stars, which are → supergiants of → spectral types O7.5 and O6. The two components are so close together that they orbit each other with a period of 14.4 days only. The Plaskett's star is a → double-line binary. The estimated masses of the components are 43 (Plaskett A) and 51 (Plaskett B) → solar masses. The lower mass component is optically brighter than the other star. Also known as HR 2422 and HD 47129 (See, e.g., Bagnuolo et al. 1992, ApJ 385, 708).

Named after the Canadian astronomer John S. Plaskett (1865-1941), who made a detailed spectroscopic study of this star in 1922.

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