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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc 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 Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg 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 > >>

Number of Results: 13116 Search : far
Vela X
  بادبان X   
Bâdbân X

Fr.: Vela X   

A compact radio source about 1500 light-years distant associated with the Vela supernova remnant. It has a nonthermal radio spectrum and is about 20 percent polarized. It is associated with the Gum Nebula, the Vela pulsar, and the X-ray source 2U 0832-45.

Vela; X for → X ray.

velocity
  تندا   
tondâ

Fr.: vitesse   

The time rate of change of position in a given direction, measured as length per unit time. → speed.

L. velocitatem (nominative velocitas) "swiftness, speed," from velox (genitive velocis) "swift."

Tondâ, from tond "swift, rapid, brisk; fierce, severe" (Mid.Pers. tund "sharp, violent;" Sogdian tund "violent;" cf. Skt. tod- "to thrust, give a push," tudáti "he thrusts;" L. tundere "to thrust, to hit" (Fr. percer, E. pierce, ultimately from L. pertusus, from p.p. of pertundere "to thrust or bore through;" PIE base *(s)teud- "to thrust, to beat") + noun suffix .

velocity curve
  خم ِ تندا   
xam-e tondâ

Fr.: courbe de vitesse   

A plot of the radial velocity of an object against time, derived from the Doppler shift of spectral lines.

velocity; → curve.

velocity dispersion
  پاشش ِ تندا   
pâšeš-e tondâ

Fr.: dispersion de vitesses   

The → standard deviation of a velocity → distribution. It indicates how objects of the sample move relative to one another. Objects with similar velocities have a small velocity dispersion, whereas objects with very different velocities have a large velocity dispersion.

velocity; → dispersion.

velocity gradient
  زینه‌ی ِ تندا   
zine-ye tondâ

Fr.: gradient de vitesse   

Fluid Mechanics: The rate at which the velocity changes with the distance across the flow. When a fluid flows past a stationary wall, the fluid right close to the wall does not move. However, away from the wall the flow speed is not zero. Therefore a velocity gradient exists, which is due to adhesive, cohesive, and frictional forces. The amount of the velocity gradient is characteristic of the fluid.

velocity; → gradient.

velocity law
  قانون ِ تندا   
qânun-e tondâ

Fr.: loi de vitesse   

In the theory of → radiation-driven winds, an equation that describes the behavior of the → wind velocity of → hot stars as a function of distance from the star. This velocity β-law is given by the expression: v(r) = v(1 - R*/r)β, where v is the → terminal velocity, R* is the stellar radius, and r the distance from the center. For → O-type stars, the exponent is estimated to be β = 0.8.

velocity; → law.

velocity of light
  تندی ِ نور، تندای ِ ~   
tondi-ye nur, tondâ-ye ~

Fr.: vitesse de la lumière   

A → physical constant which represents the ultimate speed limit for anything moving through space, according to the theory of → special relativity. It is the speed of propagation of → electromagnetic waves in a vacuum, equal to 299,792.458 km/s (nearly 3 x 108 m/s). The velocity of light appears as the connecting link between mass and energy in the → mass-energy relation. Usually denoted by c, from L. celeritas "swiftness," from celer "swift," → acceleration.

velocity; → speed; → light.

velocity pressure
  فشار ِ توانیک   
fešâr-e tavânik

Fr.: pression dynamique   

dynamic pressure.

velocity; → pressure.

velocity profile
  فراپال ِ تندا   
farâpâl-e tondâ

Fr.: profil de vitesse   

A plot of the fluid velocity as a function of position.

velocity; → profile.

velocity space
  فضای ِ تندا، ~ تنداها   
fazâ-ye tondâyi, ~ tondâhâ

Fr.: espace de vitesses   

Of a dynamical system, a three-dimensional space which consists of the set of values that the velocity can take (vx, vy, vz). → phase space.

velocity; → space.

velocity-distance relation
  باز‌آنش ِ تندا-دورا   
bâzâneš-e tondâ-durâ

Fr.: relation vitesse-distance   

The linear relation wherein all galaxies are moving away from one another, with velocities that are greater with increasing distance of the galaxy. Same as → Hubble's law.

velocity; → distance; → relation.

vena contracta
  شاره‌گذر ِ ترنگیده   
šâre-gozar-e terengidé

Fr.: veine contractée   

The location in a → fluid stream where the → cross section of the → stream is at a minimum, and fluid velocity is the highest, such as in the case of a → jet issuing out of a → nozzle.

L. vena "channel;" contracta, "contracted," → contract.

Šâre-gozar "fluid passage," → fluid; → passage, terengidé, → contracted.

Venn diagram
  نمودار ِ وِن   
nemudâr-e Venn (#)

Fr.: diagramme de Venn   

A schematic diagram using circles to represent sets and the relationships between them. Each circle represents one set. Two or more may be overlapped. The areas of overlap indicate subsets.

Named after John Venn (1834-1923), a British logician and philosopher, who introduced the diagram; → diagram.

vent
  دودکش   
dudkaš (#)

Fr.: cheminée   

The subterranean conduit from the underlying → magma chamber through which a volcano ejects igneous material. Same as volcanic vent.

M.E. venten "to furnish (a vessel) with a vent," from O.Fr. esventer "to air," from es-, → ex-, + venter, from vent, from L. ventus "wind."

Dudkaš "chimney," literally "smoke extractor," from dud, → smoke, + kaš "to extract, to draw," present stem of kešidan/kašidan "to carry, draw, protract, trail, drag" (Mid.Pers. kešidan "to draw, pull;" Av. karš- "to draw; to plow," karša- "furrow;" cf. Skt. kars-, kársati "to pull, drag, plow;" Gk. pelo, pelomai "to move, to bustle;" PIE base kwels- "to plow").

Venturi tube
  لوله‌ی ِ ونتوری   
lule-ye Venturi

Fr.: débitmètre de Venturi, tube de ~   

A → device used to → measure the → quantity of → fluid  → flowing through a → pipe.

Named after Italian physicist Giovanni Battista Venturi (1746-1822); → tube

Venus
  ناهید   
Nâhid (#)

Fr.: Vénus   

The second → planet from the → Sun, at a mean distance of roughly 108.21 × 106 km (0.72 → astronomical units). The → greatest elongation of Venus is about 47°, making it visible at most about 3 hours after sunset or before sunrise. Venus has the most circular orbit of any planet in the solar system. Venus is only slightly smaller than Earth (95% of Earth's diameter, 80% of Earth's mass). Its chemical composition and density are comparable to those of the Earth. It takes Venus just under 224.401 days to orbit the Sun, compared to the 365 day → orbital period of the Earth. Venus' rotation is → retrograde, that is it actually rotates from east to west, as opposed to west to east (→ prograde) which is the common rotating direction of most other planets. Seen from Venus, the sun would rise in the west and set in the east. Moreover, it takes about 244 Earth days for Venus to rotate once (→ sidereal rotation). This is longer than its orbital period. The length of its → solar day is about 117 Earth days. → Venus rotation. Its axial tilt is only three degrees, so there are no seasons on Venus. The → atmosphere on the surface of Venus consists mostly of → carbon dioxide, with a small trace of → nitrogen. Venus has a surface pressure about 90 times that of the Earth. See also: → Venus visibility, → transit of Venus.

O.E., from L. Venus, the goddess of beauty and love in ancient Roman mythology, from venus "love, sexual desire, beauty, charm;" PIE base *wen- "to desire, love, wish;" cf. Av. vāunuš "lovingly," vantā- "beloved one, wife;" Skt. van- "to love, desire," vanánā- "desire," vanitā- "beloved one, wife;" O.H.G. wunsc(h) "wish," wunsken "to wish."

Nâhid, planet Venus, Mid.Pers. Anahid; O.Pers. anāhita- "immaculate, unstained," goddess of pure waters and fertility, from Av. arədvī-sūra-anāhita "valient and unsustained lord of waters," from arədvī- (Skt. Saravastī) probably "she who possesses water," + sūra- "strong, powerful" (Skt. śūra- "valiant, courageous") + anāhita- "unstained," from an- negation prefix + āhita "spotted."

Venus rotation
  چرخش ِ ناهید   
carxeš-e nâhid

Fr.: rotation de Vénus   

The → sidereal rotation period of Venus, or its → sidereal day, is 243.025 Earth days (retrograde). The length of a → solar day on Venus (that is one entire day-night period) is 116.75 Earth days, that is significantly shorter than the sidereal day because of the retrograde rotation. One Venusian year is about 1.92 Venusian solar days.

Venus; → rotation.

Venus visibility
  پدیداری ِ ناهید   
padidâri-ye Nâhid

Fr.: visibilité de Vénus   

The conditions under which Venus can be seen from Earth as it travels in its orbit around the Sun. The → synodic period of Venus, that is the time Venus takes to be seen again from the Earth in the same position with respect to the Sun, is 583,92 days or just over 19 months. When Venus is between Earth and Sun (→ inferior conjunction) or on the far side of the sun (→ superior conjunction), it is invisible in the Sun's glare. Since its → greatest elongation from the Sun is never more than 47°, Venus appears only as "the morning star" and "the evening star." So at its greatest → western elongation Venus will rise about three hours ahead of the Sun and at its greatest → eastern elongation it will set about three hours after sunset. Its entire cycle is as follows:
Day 0: Superior conjunction, "full Venus."
Day 35: Venus appears in evening sky.
Day 221: Greatest → eastern elongation, "last quarter."
Day 271: Retrogression of Venus begins.
Day 286: Disappearance from the evening sky.
Day 292: Inferior conjunction, "new Venus."
Day 298: Venus appears in morning sky.
Day 313: Retrogression ends.
Day 362: Greatest → western elongation, "first quarter."
Day 549: Disappearance from morning sky.
Day 584: Superior conjunction, "full venus."
Therefore, Venus is visible as an evening star for 286 Earth days, as a morning star for 251 days, and is invisible for 47 days.

In addition, the orbital periods of Earth and Venus are closely correlated. After 8 Earth years or 13 Venus orbits, the two planets assume almost the same relative positions -- just 0.032 percent away from a perfect orbital resonance of 8:13. After this period of about 2920 Earth days, Venus appears just 1.5° (about 22 hours) in advance of its former position. Moreover, Venus exhibit → phases because its orbit lies within the Earth's. When Venus situated on the far side of the Sun from Earth, the planet is fully illuminated from our point of view. But its disk is small, just 10'' across, because it is nearly 300 million km away. When Venus is almost closest to Earth, on the near side of the Sun, it's about 60 million km away. Then it appears as a slender but much brighter crescent with a disk nearly 50'' across. See also → transit of Venus.

Venus; → visibility.

Vera C. Rubin Observatory
  نپاهشگاه ِ ورا روبین   
nepâhešgâh-e Vera C. Rubin

Fr.: Observatoire Vera C. Rubin   

A new kind of optical telescope with a 8.4-m diameter → primary mirror currently under construction in Chile and scheduled to begin operations in October 2023. Initially named Large Synoptic Survey Telescope (LSST), it will use a 3200 megapixel camera and an automated data processing system. It will have a large → field of view almost 10 square degrees of sky, or 40 times the size of the full moon. The LSST will move quickly between images to rapidly → survey the sky. From its mountain top site in the Andes (Cerro Pachon, a 2,682-m high mountain in Coquimbo Region), the LSST will take more than 800 panoramic images each night with its 3.2 billion-pixel camera, recording the entire visible sky twice each week. Each patch of sky it images will be visited 1000 times during the survey, each of its 30-second observations will be able to detect objects 10 million times fainter than visible with the human eye. The LSST's combination of telescope, mirror, camera, → data processing, and survey will capture changes in billions of faint objects. Hence, the data it provides will be used to create an animated, three-dimensional cosmic map with unprecedented depth and detail. This map will serve many purposes, from locating the → dark matter and characterizing the properties of the → dark energy, to tracking transient objects, to studying our own Milky Way Galaxy in depth. It will even be used to detect and track → potentially hazardous asteroids that might impact the Earth.

Named after Vera C. Rubin (1928-2016) whose work on galaxy rotation rates supported the existence of dark matter in galactic halos.

verb
  کرواز   
karvâz

Fr.: verbe   

A member of a major category of words that refers to an action or a state. Verbs present a complex system of forms in Indo-European languages. The set of → inflectional forms of a verb is called a → conjugation. Verbs are usually distinguished for person and number along with tense and mood (if applicable).

M.E., from O.Fr. verbe from L. verbum "verb," originally "a word," from PIE root *wer- "to speak;" cf. Av. urvāta- "command;" Skt. vrata- "command, vow;" Gk. rhetor "public speaker," eirein "to speak, say;" Lith. vardas "name;" Goth. waurd, O.E. "word."

Karvâz, literally "action word," from kar- present stem of kardan "to do, make" (Mid.Pers. kardan; O.Pers./Av. kar- "to do, make, build," Av. kərənaoiti "he makes;" cf. Skt. kr- "to do, to make," krnoti "he makes, he does," karoti "he makes, he does," karma "act, deed;" PIE base kwer- "to do, to make") + vâz "word," variants vâž, âvâz, vâj, vât, vâ, → voice.

<< < -es -iv -ti 21 a p abe abs abs aca acc acc acr act ada adh Adr aer aga air Alf Alg alk Alp alt alu amm ana And ang ani ano ant ant Ap apo app app Aqu Arc arg arr asc ass ast ast asy atm ato att aur aut axi B-m bad Bal bar bar Bay Bed ber Bet bif bim bin bio bis bla ble blu Bod Bol bor bou Bra Bre bro bul C-t Cal Cam can car Car Cas cat cav cel cen cer Cha cha Cha che chl Cir cir cir Cla cli clo clu co- coc 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 Cre cri cro cub cur cyc cyl Dan dat Dav de- Deb dec dec dee def deg del Den den der det deu dew dic dif dif dil Dip dir dis dis dis dis dis diu dod Dop dou Dra dua dus dwa dyn DZ Ear ecc eco edi EHB Ein ela ele ele ele ele ell eme emp end Eng ent epi equ equ era ESP eth Eur evi exa exc exe exi exp exp ext ext ext fac fal far fec Fer fer fie fin fir fis fla Flo flu fog for for Fou fra fre fre Fro fun G s Gal gal gal Gar gau geg gen geo geo geo ger gla gly gra gra gra gra gra Gre gro GYR Had Hal hap Har HD hea hel hel Hen Her hex hig Hil hol Hoo hor hou Hub hum hyb hyd hyd hyp hys ide ign ima imp imp in- inc Ind ind ine inf inf inf ini ins ins ins int int int int Int int int int inv ion iri irr iso iso iso Jea Jor jum K c Kep Ker kin kno lab Lam Lan Lap las lat Le lef len lev lig lig lin lin lin liq Lit loc log lon lou LS lun lun Lym M s Mag mag mag mag mag mag maj man Mar mas mas mat May mea mec mel mer mes met met met mic mid mil Min Mir mix mod mod mol mon mor mov mul mur mys nan nat nav nec Nep neu New New NGC nob nom non non nor nos nuc nuc num nut obj obl obs occ oct off oli oni ope opp opt opt orb ord org orp osc out ove oxi P-w pal par par par par Pas pat pej per per per per per per pha Phe pho pho pho phy pin pla Pla pla pla pla plu poi pol pol Pol pol por pos pot Poy pre pre pre pre pri pri pri pro pro pro pro pro pro Psa pul pum Q i qua qua qua qua R A rad rad rad rad rad rad Ram Ran rat rea rea rec rec red red ref ref reg rei rel rel rem rep res res res ret rev Rho Rie ril riv rog Ros rot rul S A Sag sam sat sca sca Sch Sco Sec sec sec seg sel sem sen set Sha sha shi sho sid sig sim sin Sir ske sli Smo soc sof sol sol sol sol sou sou spa spe spe Spe spe sph spi Spi spr sta sta sta sta sta ste ste ste Sto str str sub sub sub suc sun sup sup sup sup sur swa syn syn tac tas tel tem ter tes the the the the thi thr tid til tip ton tor tou tra tra tra tra Tri tri tru tsu tur two Typ UHE ult unc uni uni uni upg 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 > >>