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: 13116 Search : far
yoke
  یوغ   
yuq (#)

Fr.: joug   

A device for joining together a pair of draft animals, especially oxen, usually consisting of a crosspiece with two bow-shaped pieces, each enclosing the head of an animal (dictionary.com).
yoke mounting.

M.E.; O.E. geoc "yoke," earlier geoht (cf. O.S. juk, Dan. aag, M.Du. joc, Du. juk, O.H.G. joh, Ger. joch, Goth. juk "yoke"); cognate with Pers. yuq, as below

Yuq "yoke," variants yuj, juh, jut, jot; Mid.Pers. jug, ayoxtan "to join, yoke;" Av. yaog- "to yoke, put to; to join, unite;" cf. Skt. yugam "yoke;" Hittite yugan "yoke;" Gk. zygon "yoke," as above, zeugnyanai "to join, unite;" L. jungere "to join," O.C.S. igo, O.Welsh iou, Lith. jungas O.E. geoc, as above; PIE base *yeug- "to join."

yoke mounting
  برنشاند ِ یوغی   
barnešând-e yuqi

Fr.: monture anglaise à berceau   

A form of → English mounting in which the → telescope is suspended inside an inclined fork, supported at both ends, and forming a → right ascension axis parallel to the Earth's → axis. The telescope pivots about the → declination axis inside two parallel forks.

yoke; → mounting.

YORP effect
  اُسکر ِ YORP   
oskar-e YORP

Fr.: effet YORP   

A phenomenon in which the rotation rate of a small asteroid changes under sunlight absorption. Photons from the Sun are absorbed by a small body and reradiated in infrared. In the process, two forces influence the object: one from the impact of the photons, providing a tiny push, and the other as a recoil effect when the object emits the absorbed energy. In the YORP effect the body's shape has a more effective role than albedo in altering the spin rate. For small asteroids (< 10 km), YORP can cause measurable changes in rotation rate. The effect can even speed up the rotation leading to disintegration. → Yarkovsky effect.

Short for Ivan Osipovich Yarkovsky, John A. O'Keefe, V. V. Radzievskii, and Stephen J. Paddockk, who developed the explanation; → effect.

yotta- (Y-)
  یوتا-   
yotta-

Fr.: yotta-   

A metric prefix denoting 1024.

On the model of → yocto-.

young
  جوان   
javân

Fr.: jeune   

Being in the first or early stage of existence or evolution; e.g. → young stellar object.

M.E.; O.E. geong "youthful, young," from P.Gmc. *jungas (cf. O.S., O.Fris. jung, O.N. ungr, M.Du. jonc, Du. jong, O.H.G., Ger. jung, Goth. juggs), from PIE base *yeu- "vital force, youthful vigor;" cognate with Pers. javân, as below.

Javân "young;" Mid.Pers. juwân "young, youth;" Arm. yavanak (loaned from Mid.Pers.); Av. yuuan- "youth;" cf. Skt. yuvan- "young, youth;" L. juvenis "young man;" Lith. jaunas "young;" O.C.S. junu, Rus. junyj "young;" cognate with E. young, as above.

young stellar object (YSO)
  بر آخت ِ ستاره‌ای ِ جوان   
barâxt-e setâreyi-ye javân

Fr.: objet stellaire jeune   

Any star that has evolved past the → protostar stage, but has not yet arrived on the → main sequence. There is a variety of YSOs depending on their age, mass, and environment, including → Herbig stars, → T Tauri stars, and, in general, compact infrared sources embedded in molecular clouds.

young; → stellar; → object.

Young's experiment
  آزمایش ِ یانگ   
âzmâyeš-e Young (#)

Fr.: expérience de Young   

A method of producing → interference of light. Two beams of → coherent light are produced by passing light through a very small circular aperture in one screen, then through two small circular apertures very close together in a second screen. On a third screen, behind the second screen, there will be two overlapping sets of waves and, if the light is monochromatic, → interference fringes will appear on the third screen. The experiment can also be performed with a beam of electrons or atoms, showing similar interference patterns. Young's experiment provides an evidence of the → wave-particle duality, as explained by → quantum mechanics. Same as → double-slit experiment.

Named after the English scientist Thomas Young (1773-1829), who originally performed the experiment some time around 1801 in an attempt to resolve the question of whether light was composed of particles (the → corpuscular theory of light); or rather consisted of waves travelling through some → ether. The experiment proved the wave nature of light; → experiment.

Young's modulus
  پیمون ِ یانگ   
peymun-e Young

Fr.: module de Young   

A measure of elasticity of a material, defined as the ratio of tensile → stress to tensile → strain, which equals the ratio of compressive stress to compressive strain.

Named after Thomas Young, → Young's experiment.

youth paradox
  پارادخش ِ جوانی   
pârâdaxš-e javâni

Fr.: paradoxe de jeunesse   

Same as → paradox of youth.

ytterbium
  ایتربیوم   
iterbiom (#)

Fr.: ytterbium   

A soft, malleable, silver-white metallic chemical element; symbol Yb. Atomic number 70; atomic weight 173.04; melting point 819°C; boiling point about 1,194°C; specific gravity about 7.0. It has several radioactive isotopes.

From Ytterby, the name of the Swedish village where the mineral ytterbite (the source of ytterbium) was originally found. It was discovered by the Swiss chemist Jean-Charles Galissard de Marignac in 1878.

yttrium
  ایتریوم   
itriom (#)

Fr.: yttrium   

A highly crystalline iron-gray metallic chemical element; symbol Y. Atomic number 39; atomic weight 88.9059; melting point about 1,522°C; boiling point 3,338°C; specific gravity about 4.45. It has several radioactive isotopes.

From ytterbite, → ytterbium, which turnd out to be containing two different elements.

Yukawa potential
  توند ِ یوکاوا   
tavand-e Yukawa

Fr.: potentiel de Yukawa   

The potential function that is associated with the strong, short-ranged force resulting from the exchange of massive particles between two → nucleons in the same atomic nucleus. The potential has the form of V(r) = C. (1/r) exp (-K.r), where r is the distance between the nucleons and C and K are constants, giving measures of the strength and range of the force respectively.

In honor of the Japanese physicist Hideki Yukawa (1907-1981), winner of the 1949 Nobel Prize in Physics; → potential.

Z boson
  بوسون ِ Z   
boson-e Z

Fr.: boson Z   

An electrically neutral subatomic particle that along with → W boson mediates the → weak nuclear force. Like the photon, the Z boson is its own antiparticle.

boson.

Z Canis Majoris (Z CMa)
     
Z CMa

Fr.: Z CMa   

A luminous → FU Orionis object consisting of two young stars in a → binary system, a → Herbig Be star embedded in a dust cocoon and a less massive component located 0.1 arcsecond south-east. It is associated with a very large-scale and high-velocity → bipolar outflow extending in total 3.6 pc (for a distance of 1150 pc) with radial velocities up to -620 km/sec. The outflow is traced by a → jet and at least 15 → Herbig-Haro objects. In 2008 Z CMa showed the largest "outburst" ever reported in the past 90 years.

Canis Major.

Z source
  خن ِ Z   
xan-e Z

Fr.: source Z   

A member of a class of → low-mass X-ray binary systems containing low-magnetic field → neutron stars. See also → atoll source.

The name derives from the fact that on X-ray → color-color diagrams Z sources usually form a Z shape that is traced on timescales of hours to days; → source

Z-number
  عدد ِ اتمی   
adad-e atomi (#)

Fr.: nombre atomique   

Same as → atomic number.

Z, from the German word Zahl "number, numeral, figure," which was used to specify an element's numerical place in the → periodic table; → number.

Zanstra method
  روش ِ زنسترا   
raveš-e Zanstra

Fr.: méthode de Zanstra   

The method of using the nebular observations to estimate the stellar ultraviolet radiation and the temperature of the central star in a planetary nebula. The basic assumptions are that the flux from a star could be approximately represented by the Planck function and that the nebula absorbs all the ultraviolet photons from the star which can cause ionization. For each ultraviolet photon absorbed an Hα photon is emitted when the ionized hydrogen subsequently recombines with an electron. Thus the strength of the Hα line is related to the ultraviolet flux of the star. However, modern theoretical work on stellar atmospheres shows that there are important deviations between the emergent fluxes from stars and Planck functions. Moreover, some of the stellar ultraviolet photons may be missed.

Named after the Dutch astrophysicist Herman Zanstra (1894-1972), who first introduced the method in 1927.

Zeeman effect
  اُسکر ِ زیمن   
oskar-e Zeeman

Fr.: effet Zeeman   

The splitting of spectral lines into closely-spaced components when the radiating substance is placed in a strong → magnetic field. Distinction is made between the normal and → anomalous Zeeman effects, and also the longitudinal and transverse Zeeman effects. In the normal → longitudinal Zeeman effect each spectral line is split into two components with frequencies ν ± Δν. In the normal → transverse Zeeman effect un un-displaced line is observed along with a doublet, i.e. three lines in all, with the frequencies ν and ν ±Δν. In the classical theory of the normal Zeeman effect, the motion of an electron in an atom is regarded as the harmonic oscillation of a linear harmonic oscillator. Arbitrary linearly polarized oscillation of the electron can be resolved into two oscillations: one along the magnetic field and the other in a plane perpendicular to this field. The latter can be further resolved into two oscillations, circularly polarized with opposite directions of rotation that occur in the Larmor precession frequency. Classical theory cannot explain the anomalous Zeeman effect. Both effects are accounted for in quantum mechanics as the result of changes in the energy levels of atomic electrons due to the interaction of their → orbital angular momentum and → spin angular momentum with each other and with the external magnetic field. See also → inverse Zeeman effect.

Named after Pieter Zeeman (1865-1943), Dutch physicist who discovered the phenomenon; → effect.

zenith
  سرسو   
sarsu (#)

Fr.: zénith   

The point on the celestial sphere directly above the observer's head, opposite to the direction in which gravity acts. Opposite of → nadir.

M.E. cenith, from O.Fr. cenith, from M.L. cenit, senit, incorrect transliteration of Ar. samt (سمت) "path, direction," abbreviation of samt ar-ras (سمت‌الرأس), literally "road above one's head."

Sarsu, literally "the way over the head," from sarhead + su, → direction.

zenith distance
  دورای ِ سرسو، دوری ِ ~   
durâ-ye sarsu, duri-ye ~

Fr.: distance zénithale   

The angular distance of a celestial body from the zenith. The zenith distance is 90° minus the body's altitude above the horizon (i.e. the complement of the altitude) and hence is also known as coaltitude.

zenith; → distance

<< < -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 > >>