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: 888
asymptotic freedom
  آزادی ِ ناهمساوی   
âzâdi-ye nâhamsâvi

Fr.: liberté asymptotique   

The phenomenon wherein the → quarks within a → hadron get closer together, the force of containment gets weaker so that it asymptotically approaches zero for close confinement. According to → quantum chromodynamics, the quarks in close confinement are completely free to move about. On the contrary, the further we try to force the quarks apart, the greater the force of containment. The 2004 Nobel Prize in Physics was awarded to David Gross, Frank Wilczek, and David Politzer for their discovery of asymptotic freedom. This discovery established quantum chromodynamics as the correct theory of the → strong interaction.

asymptotic; → freedom.

asymptotic giant branch (AGB)
  شاخه‌ی ِ ناهمساوی ِ غولان   
šâxe-ye nâhamsâvi-ye qulân

Fr.: branche asymptotique des géantes   

A region of the → Hertzsprung-Russell diagram populated by evolving → low-mass to → intermediate-mass stars. These stars have an electron → degenerate core of carbon and oxygen surrounded by two burning shells of helium and hydrogen. The H and He-burning shells are activated alternately in the deep layers of the star. An extended and tenuous convection envelope, having a radius of 104-105 times the size of the core, lies above these shells. The loosely bound envelope is gradually eroded by the strong → stellar wind, which forms a dusty → circumstellar envelope out to several hundreds of stellar radii. The convective envelope, stellar atmosphere, and circumstellar envelope have a rich and changing chemical composition provided by → nucleosynthesis processes in the burning shells in the deep interior.

symptotic; → giant; → branch.

asymptotic velocity
  تندای ِ ناهمساوی   
tondâ-ye nâhamsâvi

Fr.: vitesse asymptotique   

For → stellar winds, same as → terminal velocity.

asymptotic; → velocity.

Atacama Large Millimeter Array (ALMA)
  آرست ِ بزرگ ِ میلیمتری ِ آتاکاما   
ârast-e bozorg-e milimetri-ye âtâkâmâ (ALMA)

Fr.: ALMA   

One of the largest ground-based astronomy projects and a major new facility for world astronomy located on the plain of the → Chajnantor Chilean Andes, San Pedro de Atacama, some 5000 m above sea level. ALMA will initially comprise 66 high precision antennas, with the option to expand in the future. There will be an array of fifty 12 m antennas, acting together as an → interferometer to capture → millimeter and → submillimeter wavelengths of 0.3 to 9.6 mm. It will have reconfigurable baselines ranging from 15 m to 18 km. A compact array of 7 m antenna and few 12 m diameter antennas (ACA) will be used to measure the diffuse emission. Resolutions as fine as 0''.005 will be achieved at the highest frequencies. Construction of ALMA started in 2003 and will be completed in 2012. The ALMA project is an international collaboration between Europe, Japan, and North America in cooperation with the Republic of Chile. ALMA is funded in Europe by the → European Southern Observatory (ESO). The first 12 m diameter antenna, built by Mitsubishi Electric Corporation for the National Astronomical Observatory of Japan, was handed over to ESO in 2008. It will shortly be joined by North American and European antennas. ALMA will allow astronomers to study the cool Universe, i.e. the molecular gas and tiny dust grains from which stars, planetary systems, galaxies, and even life are formed.

Atacama the name of a desert, west of the Andes mountains in Chile, covering a 1,000 km strip of land on the Pacific coast of South America; → large; → millimeter; → submillimeter; → array.

Aten asteroid
  سیارک ِ آتن   
sayyârak-e Aten

Fr.: astéroïde Aten   

A member of a class of → near-Earth asteroids with → perihelion distances between 0.983 and 1.0 → astronomical units. It is estimated that 6% of the total number of NEAs are Atens.

Aten; → asteroid.

atheism
  یزدان-ناباوری، خدا-ناباوری، ا-یزدان-باوری   
yazdân-nâbâvari, xodâ-nâbâvari, a-yazdân-bâvari

Fr.: athée   

1) The doctrine or belief that there is no → God.
2) Disbelief in the existence of a supreme being or beings.

a-; → theism.

Atlantic
  اتلسی   
Atlasi (#)

Fr.: atlantique   

Of or pertaining to the Atlantic Ocean.

M.E., from L. Atlanticum (mare) "the Atlantic (ocean)," from Gk. Atlantikos "of Atlas," adj. of → Atlas, in reference to Mount Atlas in NW Africa. So called because it lay beyond that mountain.

Atlas
  اتلس   
1) Atlas (#); 2) atlas (#); 3) Atlas

Fr.: Atlas   

1) The second of → Saturn's known satellites. It has a diameter of about 30 km and orbits Saturn between the outer edge of the A ring and the F ring at a mean distance of about 137,600 km. It was discovered by Richard Terrile in 1980 from Voyager 1 photos. Also known as Saturn XV.
2) A bound collection of maps often including illustrations and informative texts.
3) A blue star of visual magnitude V = 3.63, B - V = -0.09, and spectral type B8 III in the → Pleiades. Other designations: 27 Tauri, HR 1178, HD 23850. It is in fact a → triple system.

In Gk. mythology, Atlas a son of the Titan → Iapetus and the nymph Clymene. After the Titans revolted and lost a war against Zeus, Atlas was condemned by Zeus to stand forever holding up the heavens. He was identified with the Atlas Mountains in NW Africa.

atmosphere
  جو، هواسپهر   
javv (#), havâsepehr

Fr.: atmosphère   

1) The gaseous envelope surrounding a star, planet, or moon. Several solar system planets retain considerable atmospheres, due to their strong gravitational force. The gas motions in the planetary atmosphere, as a response to the heating, coupled with the rotation forces, generate the meteorological systems. The planetary satellites → Titan and → Triton also have atmospheres (M.S.: SDE).
2) A unit of pressure, called standard atmosphere, which is the pressure of air balanced by a column of mercury 76 cm high with a density of the mercury of 13.595 g/cm3 at normal acceleration of gravity. Such a column applies a pressure equal to its weight to each square cm, or 1.01325 x 106 dynes/cm2 = 1.01325 x 105 N/m2. Since this pressure is equal to 1.03323 kilograms of force per square centimeter, instead of it use is often made of the technical atmosphere (at), exactly equal to 1 kgf/cm2.

New L. atmosphaera, from Gk. atmos "vapor" + spharia "sphere."

Havâsepehr, from Mod.Pers. havâ, → air, + sepehr, → sphere. Javv "air, atmosphere," from Ar. jauw.

atmospheric
  جوی، هواسپهری   
javvi, havâsepehri (#)

Fr.: atmosphérique   

Pertaining to or existing in the atmosphere of an astronomical object such as a planet, moon, or star.

atmosphere; → -ic.

atmospheric absorption
  درشم ِ جوی   
daršam-e javvi

Fr.: absorption atmosphérique   

The absorption of → electromagnetic radiation in the → atmosphere mainly by → water vapor, → carbon dioxide, and oxygen. The atmosphere introduces two more limiting factors in → remote sensing: → atmospheric scattering and → atmospheric turbulence.

atmospheric; → absorption.

atmospheric circulation
  پرهونش ِ هواسپهری   
parhuneš-e havâsepehri

Fr.: circulation atmosphérique   

The large-scale movements of air around areas of high and low pressure whereby heat is distributed on the surface of the Earth. Atmospheric motion is driven by uneven heating of the planet. The atmosphere (and ocean) → transfers the excess heat from → tropics to → poles. The flow is determined by balance between → pressure gradients and the → Coriolis effect.

atmospheric; → circulation.

atmospheric dispersion
  پاشش ِ جوی   
pâšeš-e javvi

Fr.: dispersion atmosphérique   

The splitting of starlight into a spectrum in the atmosphere because the atmosphere acts as a refracting prism. This phenomenon brings about a practical problem for spectroscopic observations using a slit. → differential refraction; → atmospheric refraction.

atmospheric; → dispersion.

atmospheric emission
  گسیل ِ جوی   
gosil-e javvi

Fr.: émission atmosphérique   

The emission of electromagnetic radiation from the atmosphere due to thermal and → non-thermal processes. → Thermal emission comes mainly from → water vapor. Non-thermal processes result in emission lines oxygen (optical) and OH (near-IR). Atmospheric emission is a very significant source of noise in astronomical observations. See also → airglow, → aurora.

atmospheric; → emission.

atmospheric extinction
  خاموشی ِ جوی   
xâmuši-ye javvi

Fr.: extinction atmosphérique   

The decrease in the intensity of light from a celestial body due to absorption and scattering by Earth's atmosphere. It increases from the zenith to the horizon and affects short wavelengths more than long wavelengths, so that objects near the horizon appear redder than they do at the zenith.

atmospheric; → extinction.

atmospheric neutrino
  نوترینو‌ی ِ جوی   
notrino-ye javvi

Fr.: neutrino atmosphérique   

A neutrino produced in the collision of → cosmic rays (typically → protons) with nuclei in the → upper atmosphere. This creates a shower of → hadrons, mostly → pions. The pions decay to a → muon and a muon neutrino. The muons decay to an → electron, another muon neutrino, and an electron neutrino.

atmospheric; → neutrino.

atmospheric noise
  نوفه‌ی ِ جوی   
nufe-ye javvi

Fr.: bruit atmosphérique   

Noise in radio wavelengths caused by natural atmospheric processes, mainly lightening discharges in thunderstorms. They can affect radio observations.

atmospheric; → noise.

atmospheric refraction
  شکست ِ جوی   
šekast-e javvi

Fr.: réfraction atmosphérique   

The shift in apparent direction of a celestial object caused by the bending of light while passing through the Earth's atmosphere. Since the density of the atmosphere decreases with altitude, the starlight will bend more as it continues down through the atmosphere. As a result, a star will appear higher in the sky than its true direction.

atmospheric; → refraction.

atmospheric scattering
  پراکنش ِ جوی   
parâkaneš-e javvi

Fr.: diffusion atmosphérique   

The → scattering of → electromagnetic radiation by various particles in the Earth's → atmosphere. The phenomenon is caused by collisions between photons and several scattering agents such as atoms, molecules, → aerosols, and water droplets in clouds. → Rayleigh scattering.

atmospheric; → scattering.

atmospheric turbulence
  آشوبناکی ِ جوی   
âšubnâki-ye javvi

Fr.: turbulence atmosphérique   

Random fluctuations of the atmosphere caused by the constant injection of energy into the atmosphere from solar and local sources, changing the temperature and pressure of the air where it is absorbed and leading to fluid instabilities. The development over time of the instabilities gives rise to fluctuations in the density of air, and therefore the → refractive index of the atmosphere. → turbulence; → seeing.

atmospheric; → turbulence.

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