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

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 445
hyperbolic orbit
  مدار ِ هذلولی   
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
  سینوس ِ هذلولی   
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) (ex - e-x).

hyperbolic; → sine.

hyperbolic space
  فضای ِ هذلولی   
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
  هذلولی‌وار   
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
  اَبَرنازک   
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
  ساختار ِ اَبَرنازک   
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; → structure.

hyperfine transition
  گذرش ِ اَبَرنازک   
gozareš-e abar-nâzok

Fr.: transition hyperfine   

An → atomic transition involving a → hyperfine structure.

hyperfine; → transition.

hypergalaxy
  اَبَرکهکشان، هیپرکهکشان   
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.

hyper- + → galaxy.

hypergiant star
  ستاره‌ی ِ هیپرغول   
setâre-ye hiperqul

Fr.: hypergéante   

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.

hyper-; → giant.

Hyperion (Saturn VII)
  هوپریون   
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
  دوربینی   
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
  هیپرنو‌اَختر   
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.

hyper-; → nova.

hyperon
  هیپرون   
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
  هیپرصدایی   
hipersedâyi

Fr.: hypersonique   

In aerodynamics, adjective used to describe a → sound speed in excess of Mach 5. See also → supersonic.

Hypersonic, from → hyper- + → sonic.

hypervelocity star (HVS)
  ستاره‌ی ِ هیپرتند   
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:
1) → Tidal disruption of → close binary stars by the central SMBH of the Milky Way. In this process one star is captured by the SMBH while the other is ejected at high speed via the → gravitational slingshot mechanism.
2) Exchange encounters in other dense stellar environments between hard binaries (→ hard binary) and → massive stars may cause stars to be ejected and escape our Galaxy.
3) Disruption of close binaries via → supernova explosions. The → runaway velocities of both ejected stars can reach large values when asymmetric supernovae are considered, i.e. when the newborn → neutron star receives a momentum kick at birth.
(see, e.g., T. M. Tauris, 2014, and references therein, arXiv:1412.0657).

hyper-; → velocity; → star.

hypo-
  اوپا-   
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. "with," from abâ; cf. Skt. úpa (adv., prevb., prep.) "toward, with, under, on;" cognate with Gk. hypo, as above.

hypocycloid
  اوپاچرخ‌زاد   
upâcarxzâd

Fr.: hypocycloïde   

A curve generated by the trace of a fixed point on a small circle that rolls within a larger circle.

Hypocycloid, from → hypo- + → cycloid.

hypotenuse
  وتر   
vatar (#)

Fr.: hypoténuse   

In a → right triangle, the side opposite to the right angle.

L.L. hypotenusa, from Gk. hypoteinousa "stretching under" (the right angle), from hypoteinein, from → hypo- "under" + teinein "to stretch," → tension.

Vatar loan from Ar.

hypothermia
  اوپاگرمایی   
upâgarmâyi

Fr.: hypothermie   

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.

hypothesis
  انگاره   
engâré (#)

Fr.: hypothèse   

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."

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