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.
Fr.: sinus hyperbolique
A function, denoted cosh x, defined for all real values of x, by the relation: cosh x = (1/2) (ex - e-x).
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.
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.
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.
Fr.: transition hyperfine
A high luminosity star with absolute visual magnitude around -10, about 106 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)
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.
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).
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.
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).
hypervelocity star (HVS)
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:
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.
A curve generated by the trace of a fixed point on a small circle that rolls within a larger circle.
In a → right triangle, the side opposite to the right angle.
Vatar loan from Ar.
The failure of the body to maintain adequate production of heat under conditions of extreme cold.
Hypothermia, from → hypo- + therm, from Gk. therme "heat," from PIE *ghwerm-/*ghworm- "warm;" cf. Pers. garm "warm;" L. fornax "an oven;" O.E. wearm "warm" + -ia a noun suffix.
Upâgarmâyi, from upâ-, → hypo-, + garmâ "heat, warmth," from Mid.Pers. garmâg; O.Pers./Av. garəma- "hot, warm;" cf. Skt. gharmah "heat;" Gk. thermos "warm;" L. formus "warm," fornax "oven;" P.Gmc. *warmaz; O.E. wearm; E. warm; O.H.G., Ger. warm; PIE *ghworm-/*ghwerm- "warm" + -yi noun suffix.
A statement which is based on previous observations and which serves as a starting point for further investigation by which it may be proved or disproved. See also → theory, → model, → ad hoc hypothesis, → Kant-Laplace hypothesis, → arge number hypothesis, → nebular hypothesis, → null hypothesis, → statistical hypothesis, → statistical hypothesis testing.
Hypothesis, from M.Fr. hypothèse, from L.L. hypothesis, from Gk. hypothesis "base, basis of an argument, supposition," literally "a placing under," from → hypo- "under" + thesis "a placing, proposition," from root of tithenai "to place, put, set," didomi "I give;" from PIE base *dhe- "to put, to do;" cf. Mod.Pers. dâdan "to give," Mid.Pers. dâdan "to give," O.Pers./Av. dā- "to give, grant, yield," dadāiti "he gives;" Skt. dadáti "he gives;" L. dare "to give, offer," facere "to do, to make;" Rus. delat' "to do;" O.H.G. tuon, Ger. tun, O.E. don "to do."
Engâré, from engâridan, engâštan "to → suppose."