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: 13176 Search : far
angular diameter distance
  اپست ِ زاویه‌ای   
apest-e zâviye-yi

Fr.: distance angulaire   

1) The ratio of an object's → linear size (l) to its → angular size (δθ, in → radians), that is DA = l/δθ. It is used to convert observed angular separations into proper separations at the source.

2) In cosmology, a distance defined as the ratio of an object's physical transverse size (l) to its angular size (δθ). It is used to convert angular separations in telescope images into proper separations at the source. The angular diameter distance is defined by: DA = l / δθ. Consider a light source of size l at r = r1 and t = t1 subtending an angle δθ at the origin (r = 0, t = t0). The proper distance between the two ends of the object is related to δθ by: δθ = l / [a(t1). r1], where a(t1) is the → scale factor at the present epoch. Therefore, DA = r1 / (1 + z). The angular diameter distance has the particularity that it does not increase infinitely with z→ ∞. It gets its maximum value at a → redshift of ~ 1 and then decreases for higher z. Therefore, more distant objects appear larger in angular size. This is explained by considering the size of the Universe when the light of the object was emitted. At that time the Universe was smaller and therefore the object occupied a larger fraction of the size of the Universe. In other words, objects appear larger because the entire Universe acts as a → gravitational lense.

angular; → diameter; → distance.

angular differential imaging (ADI)
  تصویرگری ِ دگرسانه‌ای ِ زاویه‌ای   
tasvigari-ye degarsâne-yi-ye zâviye-yi

Fr.: imagerie différentielle angulaire   

A high-contrast imaging technique that reduces minute temporal and spatial → seeing fluctuations and facilitates the detection of faint point sources, in close separation from their stars. It consists of the acquisition of a sequence of images with an → altazimuth mounting telescope while the instrument field derotator is switched off. This keeps the instrument and telescope optics aligned and allows the field of view to rotate with respect to the instrument. For each image, a reference → point spread function (PSF) is constructed from other appropriately selected images of the same sequence and subtracted to remove quasistatic PSF structure (Marois et al. 2006, ApJ 641, 556).

angular; → differential; → imaging.

angular dispersion
  پاشش ِ زاویه‌ای   
pâšeš-e zâvie-yi

Fr.: dispersion angulaire   

The rate of change of the angles of emergence θ of various wavelengths from a dispersing prism: dθ/dλ.

angular; → dispersion.

angular distance
  اپست ِ زاویه‌ای   
apest-e zâviye-yi

Fr.: distance angulaire   

Between two points A and B, the angle → subtended by lines drawn from an observing point O to A and B. Same as → angular separation.

angular; → distance.

angular frequency
  بسامد ِ زاویه‌ای   
basâmad-e zaviye-yi (#)

Fr.: fréquence angulaire   

The number of complete rotations per unit time, expressed in radian per second: ω = 2πν, where ν is the frequency (cycles per second).

angular; → frequency.

angular kinetic energy
  کاروژ ِ جنبشی ِ زاویه‌ای   
kâruž-e jonbeši-ye zâviye-yi

Fr.: énergie cinétique angulaier   

Same as → rotational energy.

angular; → kinetic; → energy.

angular momentum
  جنباک ِ زاویه‌ای   
jonbâk-e zâviye-yi

Fr.: moment angulaire, moment cinétique   

The product of → moment of inertia and → angular velocity; synonymous with moment of momentum about an axis. Angular momentum is a vector quantity; it is conserved in an isolated system.

angular; → momentum.

angular momentum catastrophe
  نگونزار ِ جنباک ِ زاویه‌ای   
negunzâr-e jonbâk-e zâviye-yi

Fr.: catastrophe du moment angulaire   

A problem encountered by the → cold dark matter model of galaxy formation. The model predicts too small systems lacking → angular momentum, in contrast to real, observed galaxies. → cusp problem; → missing dwarfs.

angular; → momentum; → catastrophe

angular momentum parameter
  پارامون ِ جنباک ِ زاویه‌ای   
pârâmun-e jonbâk-e zâviye-yi

Fr.: paramètre de moment angulaire   

The ratio J/M, where J is the → angular momentum of a → rotating black hole and M the mass of the black hole.

angular; → momentum; → parameter.

angular momentum problem
  پراسه‌ی ِ جنباک ِ زاویه‌ای   
parâse-ye jonbâk-e zâviye-yi

Fr.: problème de moment angulaire   

1) The fact that the Sun, which contains 99.9% of the mass of the → solar system, accounts for about 2% of the total → angular momentum of the solar system. The problem of outward → angular momentum transfer has been a main topic of interest for models attempting to explain the origin of the solar system.
2) More generally, in star formation studies, the question of the origin of the angular momentum of a star and the evolution of its distribution during the early history of a star. Consider a filamentary molecular cloud with a length of 10 pc and a radius of 0.2 pc, rotating about its long axis with a typical → angular velocity of Ω = 10-15 s-1. At a matter density of 20 cm-3, the cloud is about 1 → solar mass. The cloud collapses to form a star with radius of 6 x 1010 cm. The conservation of angular momentum (∝ ΩR2) requires that as the radius decreases from 0.2 pc to the stellar value, a factor of 107, the value of Ω must increase by 14 orders of magnitude to 10-1 s-1. The star's rotational velocity will be 20% the speed of light and the ratio of → centrifugal force to gravity at the equator will be about 104. Observational data, however, indicate that the youngest stars are in fact rotating quite slowly, with rotational velocities of 10% of the → break-up velocity. The angular momentum problem was first studied in the context of single stars forming in isolation (L. Mestel, 1965, Quart. J. R. Astron. Soc. 6, 161). For more information see, e.g., P. Bodenheimer, 1995, ARAA 33, 199; H. Zinnecker, 2004, RevMexAA 22, 77; R. B. Larson, 2010, Rep. Prog. Phys. 73, 014901, and references therein.

angular; → momentum; → problem.

angular momentum transfer
  تراوژ ِ جنباک ِ زاویه‌ای   
tarâvaž-e jonbâk-e zâviye-yi

Fr.: transfert de moment angulaire   

A process whereby in a rotating, non-solid system matter is displaced toward (→ accretion) or away from (→ mass loss) the rotation center. See also → magnetorotational instability.

angular; → momentum; → transfer.

angular momentum transport
  ترابرد ِ جنباک ِ زاویه‌ای   
tarâbord-e jonbâk-e zâviye-yi

Fr.: transfert de moment angulaire   

Same as → angular momentum transfer.

angular; → momentum; → transport.

angular power spectrum
  بیناب ِ توانی ِ زاویه‌ای   
binâb-e tavâni-ye zâviye-yi

Fr.: spectre de puissance angulaire   

Of the → cosmic microwave background radiation, a plot of how much the temperature varies from point to point on the sky versus the angular frequency. This spectrum answers fundamental questions about the nature of the Universe. → cosmic microwave background anisotropy; → dipole anisotropy.

angular; → power; → spectrum.

angular resolution
  واگشود ِ زاویه‌ای   
vâgošud-e zâviye-yi

Fr.: résolution angulaire   

Of a telescope, the smallest angle betwwen two → point sources that produces distinct images. It depends on both the wavelength at which observations are made and on the diameter of the telescope. Same as → spatial resolution.

angular; → resolution.

angular separation
  جدایی ِ زاویه‌ای   
jodâyiye zâviye-yi

Fr.: séparation angulaire   

Same as → angular distance.

angular; → separation.

angular size distance
  اپست ِ زاویه‌ای   
apest-e zâviye-yi

Fr.: distance angulaire   

Same as → angular diameter distance.

angular; → size; → distance.

angular velocity
  تندا‌ی ِ زاویه‌ای   
tondâ-ye zâviye-yi

Fr.: vitesse angulaire   

A measure of the angular displacement per unit time. Of a particle traveling on a circular path or a rotating body, the ratio of the angle traversed to the amount of time it takes to traverse that angle: ω = dθ/dt. For a rigid body, all lines in it rotate through the same angle in the same time, and the angular velocity is the characteristic of the body as a whole. The angular velocity is related to the linear velocity by the equation v = rω, where r is the distance of the point from the rotation axis. → vector angular velocity.

angular; → velocity.

animal
  جانور   
jânevar (#)

Fr.: animal   

Any living creature that is distinguished from plants by independent movement and responsive sense organs.

From L. animale "living being, being which breathes," neuter of animalis "animate, living; of the air," from anima "breath; soul; breeze," cognate with Pers. jân, as below.

Jânevar, jânvar, Mid.Pers. gyânwar "animal; animate," literally "living, alive; quick," from jân, Mid.Pers. (+ prefix *ui-) gyân "(breathing) soul," gyânig "spiritual, vital;" Av. viiānayā "spirit(ness)"; Proto-Iranian *HanH- "to breathe" cf. Skt. ani- "to breathe," aniti "breathes;" Gk. anemos "wind;" L. animus "soul, spirit," anima "breeze, breath, soul;" Goth. uz-anan "to exhale" (Cheung 2007) + -e epenthesis + -var possession suffix; also hen o hen "to pant;" dialects, e.g. Lori, Kurd., henâs, henâsa "breath," henowša "panting."

animate
  فرهنیدن   
farhanidan

Fr.: animer   

1) To give life to; make alive; make lively or vigorous; give motion to.
2) To give an image or cartoon character the appearance of movement using animation techniques.

From L. animatus p.p. of animare "give breath to," also "to endow with a particular spirit, to give courage to," from anima "life, breath"  L. animus "soul, spirit," anima "breeze, breath, soul;" Goth. uz-anan "to exhale;" Gk. anemos "wind;" PIE root *ane- "to blow, to breathe;" cognate with Pers. jân "vital spirit, soul, mind," as below.

Farhanidan, from far- perfection prefix + han variant of jân "vital spirit, soul;" hen o hen "to pant;" Lori, Kurd., henâs, henâsa "breath," henowša "panting;" Mid.Pers. (+ prefix *ui-) gyân "(breathing) soul," gyânig "spiritual, vital;" Av. viiānayā "spirit(ness);" Proto-Iranian *HanH- "to breathe" cf. Skt. ani- "to breathe," aniti "breathes;" Gk. and L., as above, + -idan infinitive suffix.

animation
  فرهنش   
farhaneš

Fr.: animation   

1) An act or instance of animating or enlivening; the state or condition of being animated.
2) The technique of imaging successive drawings or positions of cartoons to create an illusion of movement when the film is shown as a sequence.

animate; → -tion.

<< < -es -it -sc 201 951 abe abs abs aca acc acc aco act ada adh ado aer aft air Alf alg alk alp Alt alt amb ana And ang ani ann ant ant ant apo app app Apu arc arg Arn art ass ast ast ast atm ato att aur aut avo azi bac bal bar bar bat Bea Bel bet bia big bin bio Bir bla bla blo Blu bol Boo bou box bre Bri bro bur cal cal Can cap car Car cat cau cel cen cen cha Cha cha che Chi chr cir cir civ cla clo clo CMB coa coe coh col col col com com com com com com com com Com con con con con con con con con con con con con coo cor cor cor Cos cos cos cou cou cra cri cro cry cul cur cyc D l dar dat day dea dec dec dec def def deg Del Den dep der det deu dew dic dif dif dil dip dir dis dis dis dis dis diu dog Dop dou Dra Dsc dus dwa dyn Dys Ear ecc eco edg egg Ein Ela ele ele ele ele ell eme emp enc eng ent epi equ equ equ eru eth Eur eve exa exc exe exi exo exp ext ext ext fab fai Fan fea fem fer fie fil fir fir fla fli flu foc for for for fra fre fre fri fun fuz gal gal gal Gam gau Gau gen geo geo geo geo Gib glo gov gra gra gra gra gre gro Gui H-a hal Ham har Hay hea hei hel Hel her het hie hig hoa hom hor hot Hub Hug hur hyd hyd hyl hyp ice ide ima ima imp imp inc inc ind ine inf inf inf ing inn ins ins int int int int int int int int inv inv ion iro Isl iso iso Jab jet Jov Jup Kar Kep kil Kip Kra Lag Lam Lan Lar las law lea Leg Leo lev lig lim lin lin lin lit loc loc log Lor low lum lun lun Lym Mac mag mag mag mag mag mai Mal map mas mas mat Mau mea mea med Men mer Mes Met met mic mic Mie mil min Mir mix mod mol mom Moo mor mov mul mur n-b nan nat nea neg Ner neu new New NGC noc nom non non nor nor nuc nuc nul nut obj obl obs occ oct off old one ope opp opt opt orb ord org Ori osc oth ove Owl P-s Pal par par par par Pas pat pec pen per per per per per Pha pha pho pho pho phy pie pix Pla pla pla pla Pli Poi pol pol pol pol por pos pos pow pre pre pre pre pri pri pri pro pro pro pro pro pro pro pub pul pyc qua qua qua qua qui rad rad rad rad rad rad rai ran rar Ray rea Rea rec rec red red ref ref reg rel rel rel ren res res res res ret rev Ric rig rin roc roo rot rot rur S5- Sal sat sca sca Sch sci Scu sec sec sed sel sel sem seq set sha she sho sid sie sil sim sin sit sky slo sno sod sol sol sol sol son sou spa spa spe spe spe spe sph spi spo squ sta sta sta sta ste ste ste Sti sto str str sub sub sub sul sup sup sup sup sur sur syl syn sys tal Tay tel ten ter tex the the the the Tho thr tid tim Tit too Tor tra tra Tra tra Tra tri Tri tru tub tur two Typ ult ult unc uni uni uni upl ura uti val var vec vel ver Ver vie vir vis vis vol W-R war wav wav wea Wei wha wid win WN3 Wol wri xen yok zen zij > >>