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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

   Homepage   
   


A B C D E F G H I J K L M N O P Q R S T U V W X Y Z

<< < "no abe acc act aff ama ani ant aps ast atm aut bar bif Boh bou cal car Cen chi Cla col com com Com con con con con con con con con con con con con cor cor Cou cur dec def Den det dif dim dis dis dou E-t edi ele ell ene ero exa exp ext fer Fla fra FU Gam geo gra gra had har hig Hub Hyp imp ind inf ins int int ion iro ite Kep lar lep lin lon lun mag mas mer mig mol Moo mut neg new New non non non nuc obs on- opt Ori oxi par per per phl pho Pla ple pol pos pre Pro pro pub qua rad rad rec red reg rem res rev rot Sak Sco sec seg sha sim sol sou sph sta ste Str sub sup T a the Tho tra tre tum uni vel vis wav wor > >>

Number of Results: 3079 Search : on
E-type chondrite
  کوندریت ِ گونه‌ی ِ E   
kondrit-e gune-ye E

Fr.: chondrite de type E   

Same as → enstatite chondrite.

enstatite; → type; → chondrite.

Earth's rotation
  چرخش ِ زمین   
carxeš-e zamin (#)

Fr.: rotation de la Terre   

The natural motion of the Earth around its own axis, which takes place once in a → sidereal day. The Earth rotates toward the → east, in the same direction as it revolves around the Sun. If viewed from the north celestial pole, the Earth turns → counterclockwise. The opposite is true when the Earth is viewed from the south celestial pole. The Earth's rotation is responsible for the diurnal cycles of day and night, and also causes the apparent movement of the Sun across the sky. The Earth's rotation velocity at the → equator is 1,673 km h-1 or about 465 m s-1. More generally, at the → latitude  φ it is given by: vφ = veq cos φ, where veq is the rotation velocity at the equator. The Earth's rotation is gradually slowing down under the action of the → tides, which are generated by the → gravitational attraction of the → Moon. As the result of this → tidal friction, the day is becoming longer at a rate of about 2 milliseconds, or 0.002 seconds, per century (or one second every 50,000 years). Moreover, the loss of the Earth's → rotational angular momentum increases the Moon's → orbital angular momentum, because the angular momentum of the → Earth-Moon system is conserved. In consequence, the Moon slowly recedes from the Earth by about 4 cm per year, which leads to increasing its orbital period and the length of a month as well.

Earth; → rotation.

Earth-Moon system
  راژمان ِ زمین-ماه   
râžmân-e Zamin-Mâh

Fr.: système Terre-Lune   

A physical system composed on the → Earth and the → Moon in which both objects directly influence each other. The total energy in the Earth-Moon system is conserved. The most notable influence that the two objects have on each other is → tides.
See also: → tidal braking, → tidal bulge, → tidal capture, → tidal coupling, → tidal disruption, → tidal force, → tidal friction, → tidal heating, → tidal locking, → tidal radius, → tidal stretching.

Earth; → Moon; → system.

eastern elongation
  درازش ِ خاوری   
derâzeš-e xâvari

Fr.: élongation est   

The position of a planet when it can be seen in the western sky just after sunset.

eastern; → elongation.

eclipse obscuration
  تیره‌شد ِ خورگرفت   
tirešod-e xorgereft

Fr.: obscuration de l'éclipse   

The fraction of the Sun's area occulted by the Moon. It should not be confused with → eclipse magnitude, which is the fraction of the Sun's diameter occulted by the Moon. Eclipse obscuration may be expressed as either a percentage or a decimal fraction (e.g., 50% or 0.50) (F. Espenak, NASA).

eclipse; obscuration, verbal noun from → obscure.

eclipse season
  فصل ِ گرفت   
fasl-e gereft

Fr.: saison d'éclipse   

The period during which the Sun is close enough to one of the → lunar orbit nodes so that an eclipse can take place. This time window lasts for 37 days for → solar eclipses and almost 24 days for → lunar eclipses. These seasons occur every 173.31 days. Two eclipse seasons make up an → eclipse year.

eclipse; → season.

ecliptic longitude
  درژنای ِ هورپهی   
derežnâ-ye hurpehi

Fr.: longitude écliptique   

One of the two coordinates in the → ecliptic system; the angle measured eastwards along the ecliptic from 0° to 360°, with the origin at the → vernal equinox.

ecliptic; → longitude.

economic
  بومداتی   
bumdâti

Fr.: économique   

1) Pertaining to the production, distribution, and use of income, wealth, and commodities.
2) Of or relating to the science of economics.
3) Pertaining to an economy, or system of organization or operation, especially of the process of production (Dictionary.com).

Adjective, from → economics.

economic growth
  رست ِ بومداتی   
rost-e bumdâti

Fr.: croissance économique   

An increase in the output that an economy produces over a period of time.

economic; → growth.

economical
  بومداتی   
bumdâti

Fr.: économique   

1) Avoiding waste or extravagance; thrifty.
2) → economic.

economic; → -al.

economics
  بومداتیک   
bumdâtik

Fr.: économie   

The science that deals with description and analysis of the production, distribution, and consumption of goods and services.

From L. oeconomicus "well ordered," from Gk. oikonomikos "practiced in the management of a household or family," from oikonomia, from oiko- "house," → eco-, + -nomia "rule, law," → -nomy; + → -ics.

Bum, → eco- + -dât, → -nomy, + -ik, → -ics.

economize
  بومداتیدن   
bumdâtidan

Fr.: économiser   

1) To practice economy; avoid waste or extravagance.
2) To manage economically; use sparingly or frugally (Dictionary.com).

From econom(y), → economy, + → -ize.

economy
  بومدات   
bumdât

Fr.: économie   

1) Thrifty and efficient use of material resources of a community, society, or household; frugality in expenditures.
2) An act or means of thrifty saving; a saving.
3) The management of the resources of a community, country, etc., especially with a view to its productivity (Dictionary.com).

From M.Fr. economie, → economics.

Bumdât, back formation from bumdâti, → economic.

Eddington factor
  کروند ِ ادینگتون   
karvand-e Eddington

Fr.: facteur d'Eddington   

Same as → Eddington parameter.

Eddington limit; → factor.

Eddington limit
  حد ِ ادینگتون   
hadd-e Eddington (#)

Fr.: limite d'Eddington   

The theoretical upper limit of → luminosity at which the → radiation pressure of a light-emitting body would exceed the body's → gravitational attraction. A star emitting radiation at greater than the Eddington limit would break up. The Eddington luminosity for a non-rotating star is expressed as: LEdd = 4πGMmpcσT-1, where G is the → gravitational constant, M the star mass, mp the → proton mass, c the → speed of light, and σT the → Thomson cross section. It can also be written as LEdd = 4πGMcκ-1, where κ is the → opacity. In terms of solar mass, the Eddington limit can be expressed by: LEdd = 1.26 × 1038 (M/Msun) erg s-1. See also → rotational Eddington limit.

Named after Arthur Stanley Eddington (1882-1944), prominent British astrophysicist; → limit.

Eddington luminosity
  تابندگی ِ ادینگتون   
tâbandegi-ye Eddington

Fr.: luminosité d'Eddington   

Same as → Eddington limit.

Eddington limit; → luminosity.

Eddington parameter
  پارامون ِ ادینگتون   
pârâmun-e Eddington

Fr.: paramètre d'Eddington   

A → dimensionless parameter indicating the degree to which a star is close to the → Eddington limit. It is expressed as Γ = L / LEdd = κ L / (4πGMc), where L and M are the star luminosity and mass respectively, κ is the opacity, c the speed of light, and G the → gravitational constant. At the Eddington limit, Γ = 1, the star would become unbound. Because stellar luminosity generally scales with a high power of the stellar mass (LM3-4), → massive stars with M larger than 10 Msun generally have electron Eddington parameters of order Γ ≅ 0.1-1.

After Arthur Stanley Eddington (1882-1944), prominent British astrophysicist; → parameter.

Eddington-Lemaître Universe
  گیتی ِ ادینگتون-لومتر   
giti-ye Eddington-Lemaître (#)

Fr.: Univers d'Eddington-Lemaître   

A theoretical model in which the → cosmological constant plays a crucial role by allowing an initial phase that is identical to the Einstein static Universe. After an arbitrarily long time, the Universe begins to expand. The difficulty with this model is that the initiation of galaxy formation may actually cause a collapse rather than initiate an → expansion of the Universe.

Eddington limit; Lemaître in honor of Georges-Henri Lemaître (1894-1966), a Belgian Roman Catholic priest, who first proposed the Big Bang theory; → universe.

Eddington-Sweet time scale
  مرپل ِ زمانی ِ ادینگتون-سوییت   
marpel-e zamâni-ye Eddington-Sweet

Fr.: échelle de temps d'Eddington-Sweet   

The time required for the redistribution of → angular momentum due to → meridional circulation. The Eddington-Sweet time for a uniformly → rotating star is expressed as: τES = τKH . GM / (Ω2 R3), where τKH is the → Kelvin-Helmholtz time scale, R, M, and L designate the radius, mass, and luminosity respectively, Ω the → angular velocity, and G the → gravitational constant. The Eddington-Sweet time scale can be approximated by τES≅ τKH / χ, where χ is the ratio of the → centrifugal force to → gravity. For the Sun, χ ≅ 10-5 resulting in an Eddington-Sweet time scale which is too long (1012 years), i.e. unimportant. In contrast, for a rotating → massive star  χ is not so much less than 1. Hence the Eddington-Sweet circulation is very important in massive stars.

Named after the prominent British astrophysicist Arthur S. Eddington (1882-1944), who was the first to suggest these currents (in The Internal Constitution of the Stars, Dover Pub. Inc., New York, 1926) and P. A. Sweet who later quantified them (1950, MNRAS 110, 548); → time scale.

edge-on galaxy
  کهکشان ِ پهلونما   
kahkašân-e pahlunemâ

Fr.: galaxie vue par la tranche   

A → spiral galaxy oriented edge-on to our view. → face-on galaxy.

edge; on, from O.E. on, variant of an "in, on, into" (cf. Du. aan; Ger. an; Goth. ana "on, upon"), from PIE base *ano "on" (cf. Av. ana "on;" Gk. ana "on, upon;" L. an-); → galaxy.

Kahkašân, → galaxy; pahlunemâ "showing the side," from pahlu, → side, + nemâ, from nemudan "to show, display," → display.

<< < "no abe acc act aff ama ani ant aps ast atm aut bar bif Boh bou cal car Cen chi Cla col com com Com con con con con con con con con con con con con cor cor Cou cur dec def Den det dif dim dis dis dou E-t edi ele ell ene ero exa exp ext fer Fla fra FU Gam geo gra gra had har hig Hub Hyp imp ind inf ins int int ion iro ite Kep lar lep lin lon lun mag mas mer mig mol Moo mut neg new New non non non nuc obs on- opt Ori oxi par per per phl pho Pla ple pol pos pre Pro pro pub qua rad rad rec red reg rem res rev rot Sak Sco sec seg sha sim sol sou sph sta ste Str sub sup T a the Tho tra tre tum uni vel vis wav wor > >>