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hyperbola hozluli (#) Fr.: hyperbole A two-branched open curve, a type of conic section, defined as the intersection between a right circular conical surface and a plane which cuts through both halves of the cone. From Gk. hyperbole "excess, exaggeration" literally "a throwing beyond," from hyperballein "to throw over or beyond," from → hyper- "beyond" + bol-, nom. stem of ballein "to throw." Hozluli, loanword from Ar. |
hyperbolic hozluli (#) Fr.: hyperbolique Of or pertaining to a → hyperbola. |
hyperbolic cosine kosinus-e hozluli Fr.: cosinus hyperbolique A function, denoted cosh x, defined for all real values of x, by the relation: cosh x = (1/2) (e^{x} + e^{-x}). → hyperbolic; → cosine. |
hyperbolic function karyâ-ye hozluli Fr.: fonction hyperbolique Any of the six functions sinh, cosh, tanh, coth, csch, and sech that are related to the → hyperbola in the same way the → trigonometric functions relate to the → circle. Many of the formulae satisfied by the hyperbolic functions are similar to corresponding formulae for the trigonometric functions, except for + and - signs. For example: cosh^{2}x - sinh^{2}x = 1. See also: → hyperbolic cosine, → hyperbolic sine. Hyperbolic functions were first introduced by the Swiss mathematician Johann Heinrich Lambert (1728-1777). → hyperbolic; → function. |
hyperbolic orbit madâr-e hozluli (#) Fr.: orbite hyperbolique An orbit that is an open curve whose ends get wider apart at any rate between that of an ellipse and a straight line. Some comets' orbits become hyperbolic through the gravitational influence of a planet the comet passes near. → hyperbolic; → orbit. |
hyperbolic sine sinus-e hozluli Fr.: sinus hyperbolique A function, denoted cosh x, defined for all real values of x, by the relation: cosh x = (1/2) (e^{x} - e^{-x}). → hyperbolic; → sine. |
hyperbolic space fazâ-ye hozluli (#) Fr.: espace hyperbolique A three-dimensional space whose geometry resembles that of a saddle-shaped surface and is said to have negative curvature. → hyperbolic; → space. |
hyperboloid hozlulivâr (#) Fr.: hyperboloïde A surface or body obtained by rotating a hyperbola about its axis of symmetry. Hyperboloid, from hyperbol(a) + → -oid a suffix meaning "resembling, like." Hozlulivâr, from hozluli, → hyperbola, + -vâr a suffix of similarity. |
hyperfine abar-nâzok Fr.: hyperfine Extremely fine or thin, especially of a → spectral line split into two or more very thin components. → hyperfine structure; → hyperfine transition. → hyper-, → fine structure. |
hyperfine structure sâxtâr-e abar-nâzok (#) Fr.: structure hyperfine In spectroscopy, the → splitting of a spectral line into a number of very thin components. It results from a small perturbation in the energy levels of atoms or molecules due to the magnetic dipole-dipole interaction arising from the interaction of the nuclear → magnetic moment with the → spin of the electron. It can be observed only at high spectral dispersion. → fine structure. |
hyperfine transition gozareš-e abar-nâzok Fr.: transition hyperfine An → atomic transition involving a → hyperfine structure. → hyperfine; → transition. |
hypergalaxy abarkahkašân, hiperkahkašân Fr.: hypergalaxie A system consisting of a dominant → spiral galaxy associated with → dwarf satellite galaxies and intergalactic matter. Examples in the → Local Group are our Galaxy and the → Andromeda galaxy. |
hypergiant star setâre-ye hiperqul Fr.: hypergéante A high luminosity star with absolute visual magnitude around -10, about 10^{6} times as luminous as the Sun. Hypergiant stars are evolved → massive stars belonging to the luminosity class Ia+ or Ia0. Their spectra show very broadened emission and absorption lines resulting from the high luminosity and low surface gravity which favor strong → stellar wind. See also → Humphreys-Davidson limit; → yellow hypergiant. |
Hyperion (Saturn VII) Huperion (#) Fr.: Hypérion The sixteenth of → Saturn's known → natural satellites. It is shaped like a potato with dimensions of 410 x 260 x 220 km and has a bizarre porous, sponge-like appearance. Many of the sponge holes or craters have bright walls, which suggests an abundance of → water → ice. The crater floors are mostly the areas of the lowest → albedo and greatest red coloration. This may be because the average temperature of roughly -180 °C might be close enough to a temperature that would cause → volatiles to → sublimate, leaving the darker materials accumulated on the crater floors. Hyperion is one of the largest bodies in the → Solar System known to be so irregular. Its density is so low that it might house a vast system of caverns inside. Hyperion rotates chaotically and revolves around Saturn at a mean distance of 1,481,100 km. It was discovered by two astronomers independently in 1848, the American William C. Bond (1789-1859) and the British William Lassell (1799-1880). Hyperion, in Gk. mythology was the Titan god of light, one of the sons of Ouranos (Heaven) and Gaia (Earth), and the father of the lights of heaven, Eos the Dawn, Helios the Sun, and Selene the Moon. |
hypermetropia durbini (#) Fr.: hypermétropie A condition of the eye that occurs when light rays entering the eye are focused behind the retina; also called farsightedness, hyperopia, long sight (opposed to → myopia). From Gk. hupermetros "beyond measure," from → hyper- + metron "measure;" → meter + -opia a combining form denoting a condition of sight or of the visual organs hemeralopia; myopia. Durbini "farsightedness," from dur "far" (Mid.Pers. dūr "far, distant, remote;" O.Pers. dūra- "far (in time or space)," dūraiy "afar, far away, far and wide;" Av. dūra-, dūirē "far," from dav- "to move away;" cf. Skt. dūrá- "far; distance (in space and time);" PIE base *deu- "to move forward, pass;" cf. Gk. den "for a long time," deros "lasting long") + bin- "to see" (present stem of didan; Mid.Pers. wyn-; O.Pers. vain- "to see;" Av. vaēn- "to see;" Skt. veda "I know;" Gk. oida "I know," idein "to see;" L. videre "to see;" PIE base *weid- "to know, to see") + -i noun suffix. |
hypernova hiper-nowaxtar Fr.: hypernova A highly energetic → supernova explosion. This phenomenon, which is more violent than a typical → supernova event, is accompanied by a → gamma-ray burst. |
hyperon hiperon (#) Fr.: hypéron An unstable elementary particles, belonging to the class called → baryons, which have greater mass than the neutron but very short lives (10^{-8} to 10^{-10} seconds). From → hyper- + → -on a suffix used in the names of elementary particles (gluon; meson; neutron; graviton, and so on). |
hypersonic hipersedâyi Fr.: hypersonique In aerodynamics, adjective used to describe a → sound speed in excess of Mach 5. See also → supersonic. |
hypervelocity star (HVS) setâre-ye hipertond Fr.: étoile hypervéloce A star whose velocity is so great that it will escape the
→ gravitational potential of our
→ Galaxy. Depending on the location and direction of
motion, this criterion typically corresponds to a stellar velocity in
the Galactic → rest frame larger than
400 km s^{-1}, and up to about 1200 km s^{-1}.
The nature of the HVSs spans a wide range of types from
→ OB stars, to metal-poor
→ F-type stars and G/K dwarfs. While there is evidence from many
late-type B HVSs in the → halo
to originate from the Galactic
→ supermassive black hole (SMBH),
other HVSs seem to originate from the → galactic disk.
HVSs can obtain their large velocities from a number of different processes: |
hypo- upâ- Fr.: hypo- A Gk. prefix denoting "under." Gk. hypo "under" (prep.), "below" (adv.); cognate with L. sub- and O.Pers./Av. upā, as below. Upâ-, from O.Pers. upā (prep.) "under, with;" Av. upā, upa (prep.; prevb) "toward, with, on, in" (upā.gam- "to arrive at," upāpa- "living in the water," upa.naxturušu "bordering on the night"); Mod.Pers. bâ "with," from abâ; cf. Skt. úpa (adv., prevb., prep.) "toward, with, under, on;" cognate with Gk. hypo, as above. |
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