An Etymological Dictionary of Astronomy and Astrophysics
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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).

Not having → symmetry.

→ asymmetry.

Lack of symmetry; not symmetrical.

Gk. asymmetria "lack of proportion," from asymmetros "ill-proportioned," from → a- "not" + symmetros "commensurable, symmetrical."

Nâhamâmuni, from nâ- "not" + hamâmuni "symmetry," from ham- "together = syn" + -â-, euphonic affix, + mun "measure" + -i, noun affix.

A straight line which is approached, but never reached, by an infinite branch of a curve, and which can be regarded as a line tangent to the curve at infinity.

Gk. asymptotos "not falling together," from → a- "not" + → syn "with" + ptotos "fallen," verbal adj. from piptein "to fall".

Nâhamsâv, literally "not touching each other," from nâ- "not" + ham "with" (akin to Gk. syn-) + sâv, agent noun of sâvidan "to touch."

Of or pertaining to an → asymptote.

Adjective from → asymptote; → -ic.

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.

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.

For → stellar winds, same as → terminal velocity.

→ asymptotic; → velocity.

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.