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

A layer of soft, partly molten, rock in the → Earth's mantle, located at a depth of 100 to 250 km, over which the more rigid plates of the → lithosphere are in motion.

Asthenosphere, from Gk. asthenes "weak" + → sphere.

Sostsepehr, from sost "weak, tender" + sepehr, → sphere.

A photographic instrument with great light gathering power which is used to photograph a large field in a single exposure.

Astrograph, from → astro- + → graph.

Axtarnegâr, from axtar, → astro-, + -negâr, → -graph.

The area of science which deals with → elementary particle and → high-energy phenomena in → astrophysics and → cosmology.

→ astro-; → particle; → physics.

The photography of stars, other celestial bodies, and stellar fields.

→ astro-, → photography.

The measurement of the intensity of light of celestial bodies.

Astrophotometry, from → astro- + → photometry.

Axtar-šidsanji, from axtar-, → astro-, + -šidsanji, → photometry.

Of or pertaining to → astrophysics.

→ astrophysics + → -al

A very fast moving, → collimated beam of → ionized gas at high temperatures associated with most classes of compact objects that spin and/or accrete matter from their surroundings, such as → protostars, → X-ray binary systems, and, at a larger scale, with → active galactic nuclei, → gamma-ray bursts, and → quasars. In general, jet sources host → accretion disks and are associated with → magnetic fields. Astrophysical jets, despite their different physical scales and power, are morphologically very similar, suggesting a common physical origin. For example, in one extreme, → active galactic nuclei jets have typical sizes ≥ 10⁶ pc, velocities near that of light c, and parent sources (→ massive black holes) with masses 10^6-9  Msun and luminosities ~ 10^43-48Lsun; while in the other extreme, → young stellar objects jets have typical sizes ≤ 1 pc, velocities ≤ 10^-3 c, and emerge from low mass protostars with masses ~ 1 Msun and luminosities (0.1-2 × 10⁴) Lsun. Jets play an important → feedback role in the evolution of their host systems. See also: → jet launching.

→ astrophysical; → jet.

An extraterrestrial → object whose physical properties and formation are studied in → astrophysics.

→ astrophysical; → object.

A scientist who studies → astrophysics.

→ astro-; → physicist. The term astrophysicist was introduced by Greenwich astronomer Edwin Dunkin in 1869.

The branch of → astronomy that deals with the → physics of → celestial objects and the → Universe in general. It relies on the assumption that the → laws of physics apply everywhere in the Universe and throughout all time. See also → observational astrophysics, → theoretical astrophysics.

Astrophysics, from → astro- "star" + → physics. The first use of the term astrophysics has been attributed to Johann Karl Friedrich Zöllner (1834-1882) in 1865. He defined it as a coalescence of physics and chemistry with astronomy (History of Astronomy: An Encyclopedia, ed. John Lankford, Routledge, 1997).

→ 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.