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

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.

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.

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

→ a-; → theism.

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.

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.

A combining form meaning "air, vapor," used in the formation of compound terms. air or vapour

From Gk. atmos "vapor."

Atmo-, loan from Gk., as above.
Havâ-, → air.

→ atmophile element.

→ atmo-; → phile.

In the → Goldschmidt classification, a → chemical element that is extremely → volatile, i.e., forms a gas or liquid at the surface of the Earth. The atmophile elements are usually concentrated in the terrestrial → atmosphere and → hydrosphere. They are → hydrogen (H), → carbon (C), → nitrogen (N), and → noble gas/qot>es, namely → helium (He), → neion (Ne), → argon (Ar), → krypton (Kr), → xenon (Xe), and → radon (Rn) (Pinti D.L., 2017, Atmophile Elements. In: White W. (eds) Encyclopedia of Geochemistry, Springer).

→ atmophile; → element.

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.

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

→ atmosphere; → -ic.

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.

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.

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.

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.

A process by which a planet loses its atmospheric gases to space. There are three main types: 1) → thermal escape, 2) → suprathermal escape (or → nonthermal escape), and 3) → impact erosion. According to models, the two mechanisms that can most efficiently cause substantial atmospheric loss are hydrodynamic escape and impact erosion (see, e.g., Catling, D. C. and Kasting, J. F., 2017, Escape of Atmospheres to Space, pp. 129-167. Cambridge University Press).

→ atmospheric; → escape.

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.

A → subatomic particle produced when → primary cosmic rays, impinge on the Earth's atmosphere producing a particle cascade, in which secondary particles decay into → muons. In the energy range up to 100 → GeV atmospheric muons come mostly from the decay of secondary → pions: π^±→ μ^± + anti-ν_μ. At higher energies, the → kaon contribution to the muon flux become significant, reaching the asymptotic value of 27% at about 10 TeV: K^±→ μ^± + anti-ν_μ.

→ atmospheric; → muon.

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.

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

→ atmospheric; → noise.

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.