An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 3079 Search : on
work function
  کریای ِ کار   
karyâ-ye kâr

Fr.: travail d'extraction   

The least amount of energy required to remove an electron from the surface of a solid, to a point just outside the solid where the electron has zero kinetic energy. See also → photoelectric effect.

work; → function.

wrong
  نادرست   
nâdorost (#)

Fr.: faux   

1) Not in accordance with what is morally right or good: a wrong deed.
2) Deviating from truth or fact; erroneous: a wrong answer.
3) Not correct in action, judgment, opinion, method, etc., as a person; in error (Dictionary.com).
See also: → false, → invalid.

M.E. wrong, wrang, O.E. wrang "twisted, crooked," from O.N. rangr "crooked, wry, wrong;" cf. Dan. vrang "crooked, wrong," Du. wrang "sour, bitter."

Nâdorost, from nâ- "not," → a-, + dorost, → right.

Wronskian
  ورونسکی   
Wronski

Fr.: Wronskien   

The → determinant of order n associated with a set of n functions, in which the first row consists of the functions, the second row consists of the first → derivatives of the functions, the third row consists of their second derivatives, and so on. For example, If y1 and y2 are functions of x, the determinant W(y1,y2) = y1 . y2' - y1' . y2 is called the Wronskian of the given function.

Named after the Polish mathematician Józef Hoene-Wroński (1776-1853).

X-ray astronomy
  اخترشناسی ِ پرتوهای ِ ایکس   
axtaršenâsi-ye partowhâ-ye iks (#)

Fr.: astronomie en rayons X   

The study of celestial bodies using their X-ray emission. X-ray astronomy deals mainly with Galactic and extragalactic phenomena involving very high-energy photon emissions, covering a band of energies between 0.1 keV and 500 keV. The research field includes: → X-ray binaries, → cataclysmic variables, → pulsars, → black holes, → dark matter, → active galaxies, → galactic clusters → X-ray transients. The Earth's atmosphere absorbs most X-rays coming from outer space. X-ray astronomy therefore requires observations to be done above atmosphere. The first rocket flight which successfully detected a cosmic source of X-ray emission was launched in 1962 by an American research group. A very bright source was detected that they named → Scorpius X-1. Since then several dedicated X-ray astronomy satellites have been launched, among which: Uhuru, INTEGRAL, ROSAT, Rossi X-ray Timing Explorer (RXTE), → Chandra X-ray Observatory, and → XMM-Newton, which have contributed to important advances in astronomy.

X-ray; → astronomy.

X-ray diffraction
  پراش ِ پرتو ِ ایکس   
parâš-e partow-e iks

Fr.: diffraction de rayons X   

The diffraction of X-rays by the atoms or ions of a crystal. The wavelength of X-rays are comparable to the size of interatomic spacings in solids. Since the atoms in a crystal are arranged in a set of regular planes, crystals serve as three-dimensional diffraction gratings for X-rays. Planes of repetition within the atomic structure of the mineral diffract the X-rays. The pattern of diffraction thus obtained is therefore used to identify minerals by bombarding them with X-rays.

X-ray; → diffraction.

X-ray Dim Isolated Neutron Star (XDINS)
  ستاره‌ی ِ نوترونی با پرتوهای ِ ایکس ِ نزار   
setâre-ye notroni bâ partowhâ-ye X-e nazâr

Fr.: étoile à neutron de faibles rayons X   

A member of a class of isolated, radio-silent → pulsars with peculiar properties. They show a purely thermal spectrum at X-ray energies with no evidence for a high-energy, power-law component often detected in other → isolated neutron star classes. The X-ray luminosity is 1031 - 1032 erg s-1, fully consistent with surface blackbody emission with temperatures ~ 40-100 eV and (radiation) radii of a few kilometers, as derived from X-ray spectral fits. With the only exception of RX J1856.5-3754, broad absorption features have been found in all XDINSs. These features have energies ~ 300 - 700 eV, equivalent widths of ~ 50 - 150 eV and, as in the case of RX J0720.4-3125, may be variable.

X-ray; → dim; → isolated; → neutron; → star.

X-ray Dissociation Region (XDR)
  ناحیه‌ی ِ واهزش ِ پرتوهای ِ ایکس   
nâhiye-ye vâhazeš-e partowhâ-ye X

Fr.: région de dissociation par rayons X   

A region of → molecular clouds whose chemistry is affected by → X-rays from neighboring sources.

X-ray; → dissociation; → region.

xenon
  گزنون   
gezenon (#)

Fr.: xénon   

A colorless, odorless, tasteless, chemically un-reactive gas, belonging to the → inert gas group, occurring in exceedingly minute amounts in the air; symbol Xe. → Atomic number 54; → atomic weight 131.29; → melting point -111.9°C; → boiling point -107.1°C. Xenon was discovered spectroscopically in 1898 by William Ramsay and M. W. Travers, who obtained it by fractional distillation of an impure sample of liquid → krypton. The lightest → isotopes of xenon (124Xe and 126Xe) are produced during → supernova explosions; intermediate-mass isotopes (127Xe, 128Xe, 129Xe, 130Xe, 131Xe and 132Xe) are produced during the → Asymptotic Giant Branch phase of evolved low- and intermediate-mass stars; the heaviest isotopes (134Xe and 136Xe) are produced during the → merger of → neutron stars.

From Gk. xenon, neuter of xenos "strange," introduced by the discoverers.

XMM-Newton
   XMM نیوتن   
XMM-Newton

Fr.: XMM-Newton   

A European Space Agency's satellite, launched on 10 December 1999 and designed for the observation of → X-rays emitted by astronomical objects. The satellite carries three very advanced X-ray telescopes. The three corresponding European Photon Imaging Cameras (EPIC) are sensitive over the energy range 0.2 keV to 12 keV. Other instruments on-board are two reflection grating spectrometers which are sensitive below about 2 keV, and a 30 cm diameter → Ritchey-Chretien optical/UV telescope. The telescope moves in a highly elliptical orbit, traveling out to nearly one third of the distance to the Moon and enabling long, uninterrupted observations of faint → X-ray sources. The original mission lifetime was two years, it has now been extended for further observations until at least 2010. Among recent results obtained using XMM-Newton one can mention an intermediate-mass black hole of over 500 solar masses in the galaxy ESO 243-49 (Nature 460, 73, 2009) and broad line emission from iron K- and L-shell transitions in the active galaxy 1H 0707-495 (Nature 459, 540, 2009). See also → X-ray astronomy.

XMM, from "X-ray Multi-Mirror;" Newton, in honor of Sir Isaac Newton, → newton.

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.

zero age horizontal branch star (ZAHB)
  ستاره‌ی ِ شاخه‌ی ِ افقی با سن ِ صفر   
setâre-ye šâxe-ye ofoqi bâ senn-e sefr

Fr.: étoile de la branche horizontale d'âge zéro   

A star that has arrived on the → horizontal branch after leaving the → red giant branch. It begins → helium burning in its core.

zero; → age; → horizontal; → branch; → star.

zero suppression
  نهاوش ِ صفر   
nehâveš-e sefr

Fr.: suppression de zéro   

The removal of non-significant zeroes from a number. For example, replacing 531.2300 by 531.23.

zero; → suppression.

Zeta Orionis
  زتا-شکارگر، زتا-اریون   
zetâ-Šekârgar, zetâ-Orion

Fr.: Zeta (ζ) Orionis   

Same as → Alnitak.

Zeta (ζ), Gk. letter in the → Bayer designation scheme.

Zhevakin's zone
  زنار ِ ژواکین   
zonaar-e Zhavakin

Fr.: zone de Zhevakin   

One of several regions of the stellar interior where increased → opacity can provide the necessary → valve mechanism to drive → stellar pulsations. Also called → partial ionization zone.

Named after the Russian astronomer Sergei A. Zhevakin (1916-2001), who identified these zone in the 1950s; → mechanism.

zircon
  زرگون   
zargun (#)

Fr.: zircon   

A common mineral, zirconium silicate, ZrSiO4, occurring in small tetragonal crystals. The color is variable, usually brown to reddish brown, but also colorless, pale yellowish, green, or blue. A red variety, used as a gem, is called hyacinth. Zircon contains trace amounts of uranium and thorium and therefore can be used for radiometric datings. Also called jargon.

From Ger. Zirkon, from Ar. zarqun "cinnabar, bright red," from Pers. zargun "gold-colored," from zargold + -gun "resembling; manner, fashion; color" (Mid.Pers. gônak "kind, species;" Av. gaona- "color").

zirconium
  زیرکونیوم   
zirkoniom (#)

Fr.: zirconium   

A metallic chemical element; symbol Zr. Atomic number 40; atomic weight 91.22; melting point about 1,852°C; boiling point 4,377°C; specific gravity 6.5 at 20°C. Zirconium was discovered in the mineral zirconia by the German chemist Martin-Heinrich Klaproth in 1789. It was first isolated by the Swedish chemist Jons Jacob Berzelius in 1824 in an impure state and finally by the chemists D. Lely Jr. and L. Hamburger in a pure state in 1914.

From → zircon.

zirconium oxide, ZrO
  اکسید ِ زیرکونیوم   
oksid-e zirkoniom

Fr.: oxide de zirconium   

A → diatomic molecule made up of → zirconium and → oxygen atoms. See → ZrO band.

zirconium; → band.

zone
  زنار   
zonâr (#)

Fr.: zone   

The portion of the surface of a sphere included between two parallel planes.

From L. zona "geographical belt, celestial zone," from Gk. zone "a belt," related to zonnynai "to gird," from PIE base *yes- "to gird, girdle;" cognate with Pers. parhun "circle," as below.

Zonâr most probably loan from from Gk., as above; it is related to Pers. parhun "circle," ultimately from Proto-Iranian *pari-iâhana- "girdle, belt," from pari-, variant pirâ-, → circum-, + iâhana- "to girdle," cf. Av. yâh- "to girdle." The Pers. pirâhan "shirt" is a variant of parhun.

zone of avoidance
  زنار ِ تسنش   
zonâr-e tosneš

Fr.: zone d'évitement, zone vide   

The region on the sky covered by the plane of the → Milky Way. It is characterized by an apparent absence of galaxies, due to the obscuring effect of → interstellar dust in the → Galactic plane.

zone; → avoidance.

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