An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 58 Search : planet

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.

sayyârak (#)

Fr.: planétoïde   

An older equivalent for → asteroid.

planet + → -oid.

sayyârešenâsi (#)

Fr.: planétologie   

Same as → planetary science.

planet; + → -logy.

post-planetary nebula star
  ستاره‌ی ِ پسا-میغ ِ سیاره‌ای   
setâre-ye pasâ-miq-e sayyâre-yi

Fr.: étoile post-nébuleuse planétaire   

An evolved star whose → planetary nebula has dissipated.

post-; → planetary; → nebula; → star.

preplanetary nebula (PPN)
  پیش-میغ ِ سیاره‌ای   
piš-miq-e sayyâre-yi

Fr.: pré-nebuleuse planétaire   

A short-lived transition object between the → asymptotic giant branch (AGB) and → planetary nebula phases. See also → post-asymptotic giant branch star (post-AGB).

pre-; → planetary; → nebula. The more commonly used term, → protoplanetary nebula, is a misnomer and must be avoided. Indeed → protoplanetary is widely used to refer to disks around → pre-main sequence stars. Since the term → protoplanet is used to denote planets undergoing formation, the use of the term "protoplanetary nebula" to mean a completely different kind of object is an unfortunate choice (Sahai et al. 2005, ApJ 620, 948).


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.

pulsar planet
  سیاره‌ی ِ پولساری، تپار ِ ~   
sayyâre-ye pulsâri, tapaar-e ~

Fr.: planète de pulsar   

A planet orbiting a → pulsar. The first such planet to be discovered was around a → millisecond pulsar known as PSR 1257+12.

pulsar; → planet.

rogue planet
  سیاره‌ی ِ ولگرد   
sayyâre-ye velgard

Fr.: planète vagabonde   

Same as → free-floating object.

rogue; → planet.

Spectro-Polarimetric High-contrast Exoplanet (SPHERE)

Fr.: Spectro-Polarimetric High-contrast Exoplanet (SPHERE)   

The → extreme adaptive optics system and → coronagraphic facility at the → European Southern Observatory (ESO) → Very Large Telescope (VLT) (UT3) available from May 2014. Its primary science goal is imaging, low-resolution spectroscopic, and polarimetric characterization of → exoplanetary system at → visible and → near-infrared wavelengths (0.5-2.32 μm). SPHERE is capable of obtaining → diffraction-limited images at 0''.02 to 0''.08 resolution depending on the wavelength. Its → spectral resolution is 30 to 350, depending on the mode.

spectro-; → polarimetric; → high; → contrast; → exoplanet.

superior planet
  سیاره‌ی ِ زبرین   
sayyâre-ye zabarin

Fr.: planète supérieure   

A planet whose orbit lies outside that of the Earth. The superior planets are Mars, Jupiter, Saturn, Uranus, and Neptune. → planet.

superior; → planet.

terrestrial planets
  سیاره‌های ِ زمینی   
sayyârehâ-ye zamini

Fr.: planètes terrestres   

The four innermost planets in the solar system, Mercury, Venus, Earth and Mars. They are called terrestrial because they have a compact, rocky surface like the Earth's. The planets, Venus, Earth, and Mars have significant atmospheres while Mercury has almost none. These planets are approximately the same size, with the Earth the largest. They are considerably denser than the Jovian planets, ranging from a specific gravity of 4 for Mars to 5.5 for the Earth.

terrestrial; → planet.

Transiting Exoplanet Survey Satellite (TESS)
  ماهواره‌ی ِ بردید ِ برون‌سیاره‌های ِ گذرنده   
mâhvâre-ye bardid-e borun-sayyârehâ-ye gozarandé


A → NASA space telescope devoted to the hunt for planets orbiting the brightest stars in the sky, launched on April 18, 2018. The mission is planned to monitor at least 200,000 stars for signs of → exoplanets using the → planetary transit method. TESS is equipped with four identical refractive → cameras with a combined → field of view (FOV) of 24 × 96 degrees. Each camera consists of a → CCD detector assembly, a → lens assembly, and a lens hood. The → entrance pupil diameter is 10.5 cm and the wavelength range 600 to 1,000 nm. The satellite is a follow-up of NASA's → Kepler spacecraft, but focuses on stars that are 30 to 100 times brighter than those Kepler examined.

transit; → exoplanet; → survey.

transiting planet
  سیاره‌ی ِ گذرنده   
sayyâre-ye gozarandé

Fr.: planète en transit   

A planet that passes in front of its star directly between Earth and the star. The → transit method is used for detecting → exoplanets around stars.

transit; → planet.

TRAnsiting Planets and PlanetesImals Small Telescope (TRAPPIST)


A Belgian facility devoted to the detection and characterization of → exoplanets and to the study of → comets (→ transiting planet) and other → small solar system bodies. It consists of two 60 cm robotic telescopes located at the → European Southern Observatory, → La Silla, in Chile and at Oukaïmden Observatory in Marroco.

transit; → planet; → planetesimal; → small; → telescope.

water planet
  سیاره‌ی ِ آبی   
sayyâre-ye âbi

Fr.: planète océan   

Same as → ocean planet.

water; → planet.

Wide Angle Search for Planets (WASP)
   WASP: جستجوی ِ سیاره با زاویه‌ی ِ گشاده   
WASP: josteju-ye sayâré bâ zâviye-ye gošâdé

Fr.: WASP: recherche à angle large de planètes   

An international collaboration, more accurately named SuperWASP, led by the United Kingdom, that aims at detecting → extrasolar planets by means of the → transit method. SuperWASP consists of two robotic observatories that operate continuously all year around, providing coverage of the sky in both hemispheres. The first, SuperWASP-North, is located on the island of La Palma. The second, SuperWASP-South, is located at the site of the South African Astronomical Observatory (SAAO). The observatories each consist of eight wide-angle cameras that simultaneously monitor the sky for → planetary transit events. Using the array of cameras makes it possible to monitor millions of stars simultaneously at an → apparent visual magnitude from about 7 to 13.

wide; → angle; → search; → planet.

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