sit-e axtaršenâsik, ~ axtaršenâxti
Fr.: site astronomique
A certain place whose characteristics, as to location, altitude, atmospheric conditions, etc., make it appropriate for astronomical observations.
Fr.: table astronomique
One of a set of tables giving parameters used for calculations of positions of the Sun, the Moon, and the planets in particular in pre-telescopic astronomy. The oldest known astronomical tables are those of Ptolemy. In Modern astronomy it is usually replaced by the term → ephemeris. Same as → zij. See also → Toledan Tables, → Alfonsine Tables.
nimtâb-e axtaršenâsik, ~ axtarsnâxti
Fr.: crépuscule astronomique
The time between sunset or sunrise and the moment when the Sun's center lies 18° below the horizon. → civil twilight.
astronomical unit (au)
yekâ-ye axtaršenâsik, ~ axtaršenâxti (#)
Fr.: unité astronomique
1) A unit of length equal to 149 597 870 700 m exactly, with symbol "au"
(re-definition at the International Astronomical Union's 28th General
Assembly in Beijing, China, August 20-31). The astronomical unit equals
1.5813 × 10-5 → light-years and
4.8481 ×10-6 → parsecs.
The science of the celestial bodies and the Universe, dealing especially with the positions, dimensions, distribution, motion, chemical composition, energy, and evolution of celestial bodies and phenomena.
O.Fr. astronomie, from L. astronomia, from Gk. astronomia, from → astro- "star" + nomos "arranging, regulating," related to nemein "to deal out."
Axtaršenâsi, from axtar "star," → astro- + -šenâsi "knowledge" from šenâxtan "to know, to discern."
Fr.: physique des astroparicules
axtar-šidnegâri, šidnegâri-ye axtari
The photography of stars, other celestial bodies, and stellar fields.
axtar-šidsanji, šidsanji-ye axtari
The measurement of the intensity of light of celestial bodies.
Of or pertaining to → astrophysics.
Fr.: jet astrophysique
Fr.: objet astrophysique
A scientist who studies → astrophysics.
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.
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 =
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.
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.
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 giant branch (AGB)
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.
Fr.: vitesse asymptotique