An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 139 Search : all
naryân (#)

Fr.: étalon   

An uncastrated adult male horse, especially one used for breeding.

M.E. stalon, from O.Fr. estalon, "uncastrated male horse," cognate with O.H.G. stal "stable," cf. O.H.G. stall "stand, place, stable, stall," Ger. Stall "stable," Stelle "place"), from PIE root *stel- "to put, stand," with derivatives referring to a standing object or place; akin to Pers. istâdan "to stand," → station.

Nariyân, from nar "male," → masculine.

statistical parallax
  دیدگشت ِ آماری   
didgašt-e âmâri

Fr.: parallaxe statistique   

The mean parallax of a group of stars that are all at approximately the same distance, as determined from their radial velocities and proper motions.

statistical; → parallax.

stellar metallicity
  فلزیگی ِ ستاره‌ای   
felezigi-ye setâre-yi

Fr.: métallicité stellaire   

The metallicity derived from observations of stars in galaxies. It is mainly based on spectral → absorption lines in → ultraviolet (UV) and optical ranges. Stellar metallicity is a direct measure of the amount of metals in a galaxy, since large part of heavy elements lies in its stars.

stellar; → metallicity.

stellar parallax
  دیدگشت ِ ستاره   
didgašt-e setâré

Fr.: parallaxe stellaire   

The apparent → difference in the → position of a → celestial object as seen by an → observer from two widely separated → locations. The parallax of an object can be used to derive its → distance. The relationship between the → parallax angle  p (measured in seconds of arc) and the distance d (measured in → astronomical units) is given by d = 206,264 / p. For a parallax angle p = 1'', the distance to the star would correspond to 206,264 AU. By convention, the distance unit → parsec is defined to be equivalent to 206,264 AU. Therefore, the parallax relation takes the much simpler form: d (in pc) = 1/p (in seconds of arc). The first star whose parallax was measured was → 61 Cygni (Bessel, 1838).
See also:
annual parallax, → diurnal parallax, → dynamical parallax, → geocentric parallax, → heliocentric parallax, → horizontal parallax, → lunar parallax, → mean parallax, → parallactic ellipse, → parsec, → photometric parallax, → secular parallax, → solar parallax, → spectroscopic parallax, → statistical parallax, → trigonometric parallax.

stellar; → parallax.

tangentially polarized light
  نور ِ قطبیده‌ی ِ سایانی   
nur-e qotbide-ye sâyâni

Fr.: lumière polarisée tangentiellement   

The → linearly polarized light that vibrates perpendicularly to an imaginary line joining the source to the point of observation.

Tangentially, adverb of → tangential; → polarized; → light.

tidally locked
  کشندانه قفل   
kešandâné qofl


The description of a → system of two bodies undergoing → tidal locking.

tidal; → -ly; → lock.

tidally stripped
  کشندانه لُختانیده   
kešandâne loxtânide

Fr.: balayé par effet de marées   

Describing a → stellar system that has undergone → tidal stripping.

tidal; → -ly; → strip.

time allocation
  تسک ِ زمان، ~ وقت   
tesk-e zamân, ~ vaqt

Fr.: attribution de temps de télescope   

The assignment of telescope time by an expert panel to proposals after evaluating the merits of the observation projects.

time; → allocation.

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.

trigonometric parallax
  دیدگشت ِ سه‌برسنجی، ~ سه‌برسنجیک   
didgašt-e sebarsanji, ~ sebarsanjik

Fr.: parallaxe trigonométrique   

The → parallax of a nearby star (less than 300 → light-years) against the background of more distant stars resulting from the motion of the Earth in its orbit around the Sun.

trigonometric; → parallax.

Two Micron All Sky Survey (2MASS)

Fr.: 2MASS   

An astronomical → survey conducted from 1997 to 2001 of the entire sky in near-infrared J, H, and K bands (wavelengths 1.25, 1.65, and 2.17 microns respectively). The aim was to detect and characterize point sources brighter than about 1 → mJy in each band, with → signal-to-noise ratio greater than 10, using a pixel size of 2".0. Two automated 1.3-m telescopes were used, one at Mt. Hopkins, AZ, and one at CTIO, Chile. 2MASS is currently producing the following data products: 1) A digital atlas of the sky comprising approximately 4 million 8' × 16' images, having about 4" spatial resolution in each of the wavelength bands. 2) A point source catalog containing accurate positions and fluxes for 300 million stars and other unresolved objects. 3) An extended source catalog containing positions and total magnitudes for more than 1,000,000 galaxies and nebulae.

two; → micron; → all-sky survey.

Tyndall effect
  اسکر ِ تیندال   
oskar-e Tyndall

Fr.: effet Tyndall   

The observation whereby when light passes through a clear fluid holding small particles in suspension, the shorter blue wavelengths are scattered more strongly than the red. The effect is most commonly known as the → Rayleigh scattering.

Names for John Tyndall (1820-1893), who discovered the effect in 1859.

universality of free fall
  هرگانیگی ِ افت ِ آزاد   
hargânigi-ye oft-e âzâd

Fr.: universlité de chute libre   

Same as → weak equivalence principle.

universality; → free; → fall.

Valles Marineris
  درّه‌های ِ مارینر   
darrehâ-ye Mariner

Fr.: Valles Marineris   

A system of canyons located just south of the Martian equator. The system is about 4000 km long. The central individual troughs, generally 50 to 100 km wide, merge into a depression as much as 600 km wide. In places the canyon floor reaches a depth of 10 km, 6 to 7 times deeper than the Grand Canyon on Earth.

L. Valles Marineris "Mariner's Valleys," named after the Mars orbiter Mariner 9, which discovered the Martian canyon in 1971-72. → valley.

darré (#)

Fr.: vallée   

A long, narrow region of low land between ranges of mountains, hills, or other high areas, often having a river or stream running along the bottom.

M.E. valeie, valey, from O.Fr. valee "valley," from V.L. *vallata, from L. vallis "valley," of unknown origin.

Darré "valley," from Mid.Pers. dar, darrak "ravine, cleft;" cf. Skt. pradará- "cleft."

Van Allen belts
  کمربندهای ِ وان آلن   
kamarbandhâ-ye Van Allen

Fr.: ceintures de Van Allen   

The ring-shaped regions of charged particles surrounding the Earth from 1 to 6 Earth radii into space. The charged particles are trapped in by the Earth's magnetic field. The inner belt is between 1.2 and 4.5 Earth radii and contains high-energy electrons and protons which originate mainly from interactions between cosmic rays and the upper atmosphere. The outer belt, located between 4.5 and 6.0 Earth radii, contains lower-energy charged particles mainly coming from the solar wind.

Named after James Van Allen (1914-2006), who discovered the belts in 1958 based on measurements made by Explorer 1, the USA's first successful artificial satellite; → belt.

very small grain (VSG)
  دانه‌ی ِ بسیار کوچک   
dâne-ye besyâr kucak

Fr.: très petit grain   

A special type of carbonaceous → interstellar dust grains with a size ranging from 10 to 150 Å and consisting of tens to hundreds of atoms. In contrast to → big grains, VSGs are not in → thermal equilibrium. They can be heated to very high temperatures (~ 1000 K) by the absorption of a single photon. It is thought that VSGs are clusters of → PAH.

very; → small; → grain.

divâr (#)

Fr.: mur   

1) An upright continuous structure that divides one area from another or surrounds an area.
2) A wall-like, enclosing part, mass, or thing .

M.E., from O.E. w(e)all "rampart, dike, cliff," also "defensive fortification around a city, side of a building" (O.Sax., O.Fris., M.L., M.Du. wal), from L. vallum "wall, rampart."

Divâr "wall," from Mid.Pers. dîvâr "wall;" related to Mid.Pers. bâr, var "enclosure, defences, fortress;" Mod.Pers. bâru "wall, rampart, fortification; fort; tower;" O.Pers. didā- "wall, stronghold, fortress;" Av. var- "castle," from var- "to cover, conceil;" Proto-Iranian *dida-vāra-; cf. Skt. dehī- "wall;" Gk. teikhos "wall;" E. dike, ditch.

white dwarf crystallization
  بلورش ِ سفیدکوتوله   
bolureš-e sefid kutulé

Fr.: cristallisation de naine blanche   

The most important phenomenon occurring during → white dwarf evolution, which results from its cooling. Crystallization is a → phase transition whereby → latent heat is released. At the cooler end of a white dwarf's life (→ cooling time), the → thermal energy of nuclei, which are positively charged ions, becomes small and the effects of electrostatic interaction on the motion of ions become important. The ions repel each other and their distribution will be such that the → Coulomb energy per ion is a minimum. This will cause the ions to form crystal-like lattice structures. As the star cystallizes it releases latent heat, providing an additional energy source that slows the cooling process compared to the → Mestel theory. Once the bulk of the white dwarf is crystalline, heat can travel through the star more easily and the white dwarf cools faster.

white; → dwarf; → crystallization.

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