An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 3079 Search : on
harmonic series
  سری ِ هماهنگ   
seri-ye hamâhang

Fr.: série harmonique   

Overtones whose frequencies are integral multiples of the → fundamental frequency. The fundamental frequency is the first harmonic.

harmonic; → series.

Harvard classification
  رده‌بندی ِ هاروارد   
radebandi-ye Hârvârd (#)

Fr.: classification de Harvard   

A classification of stellar spectra published in the Henry Draper catalogue, which was prepared in the early twentieth century by E. C. Pickering and Miss Annie Canon. It is based on the characteristic lines and bands of the chemical elements. The most important classes in order of decreasing temperatures are as follows: O, B, A, F, G, K, M.

Harvard, named for John Harvard (1607-1638), the English colonist, principal benefactor of Harvard College, now Harvard University. → classification

harvest moon
  ماه ِ خرمن‌برداری   
mâh-e xarman bardâri

Fr.: lune de moisson   

The → full moon that appears closest in time to the → autumnal equinox.

harvest; → moon.

Hawking radiation
  تابش ِ هاؤکینگ   
tâbeš-e Hawking (#)

Fr.: rayonnement de Hawking   

The radiation produced by a → black hole when → quantum mechanical effects are taken into account. According to quantum physics, large fluctuations in the → vacuum energy occurs for brief moments of time. Thereby virtual particle-antiparticle pairs are created from vacuum and annihilated. If → pair production happens just outside the → event horizon of a black hole, as soon as these particles are formed they would both experience drastically different → gravitational attractions due to the sharp gradient of force close to the black hole. One particle will accelerate toward the black hole and its partner will escape into space. The black hole used some of its → gravitational energy to produce these two particles, so it loses some of its mass if a particle escapes. This gradual loss of mass over time means the black hole eventually evaporates out of existence. See also → Bekenstein formula, → Hawking temperature.

Named after the British physicist Stephen Hawking (1942-2018), who provided the theoretical argument for the existence of the radiation in 1974; → radiation.

Hayashi forbidden zone
  زنار ِ بژکم ِ هایاشی   
zonâr-e baſkam-e Hayashi

Fr.: zone interdite de Hayashi   

The region to the right the → Hayashi track, representing objects that cannot be in → hydrostatic equilibrium. Energy transport in these objects would take place with a → superadiabatic temperature gradient.

Hayashi track; → forbidden; → zone.

He-strong star
  ستاره‌ی ِ هلیوم-سترگ   
setâre-ye heliom-sotorg

Fr.: étoile forte en hélium   

An early → B-type star showing helium lines with abnormally large equivalent widths. The surface → chemical abundances of He-strong stars are influenced by the presence of a strong → magnetic field, resulting in a He overabundance that typically varies in strength over the stellar surface. Examples include HR 735, HD 184927, and CPD-62°2124.

helium; → strong; → line.

heat conduction
  هازش ِ گرما   
hâzeš-e garmâ

Fr.: conduction de chaleur   

A type of → heat transfer by means of molecular agitation within a material without any motion of the material as a whole.

heat; → conduction.

heat convection
  همبز ِ گرما   
hambaz-e garmâ (#)

Fr.: convection de chaleur   

A type of → heat transfer involving mass motion of a fluid such as air or water when the heated fluid is caused to move away from the source of heat, carrying energy with it.

heat; → convection.

heat of vaporization
  گرمای ِ بخارش   
garmâ-ye boxâreš

Fr.: chaleur de vaporisation   

The amount of heat energy required to transform an amount of a substance from the liquid phase to the gas phase. → molar heat of vaporization.

heat; → vaporization.

heliocentric gravitational constant
  پایای ِ گرانشی هورمرکزی   
pâyâ-ye gerâneši-ye hur-markazi

Fr.: constante gravitationnelle héliocentrique   

A parameter representing the product of the → gravitational constant by the → solar mass. It is 13.27 x 1019 m3 s-2.

heliocentric; → gravitational; → constant.

helium-argon calibration
  کبیزش ِ هلیوم-آرگون   
kabizeš-e heliyom-ârgon

Fr.: calibration hélium-argon   

A wavelength calibration of astronomical spectra using a helium-argon light source.

helium; → argon; → calibration.

helium-argon lamp
  لامپ ِ هلیوم-آرگون   
lâmp-e heliyom-ârgon (#)

Fr.: lampe hélium-argon   

A comparison light source containing the known spectral lines of helium and Argon.

helium; → argon; → lamp.

heptagon
  هفت‌بر، هفت‌گوش   
haftbar (#), haftguš (#)

Fr.: heptagone   

A → polygon with seven → angles and seven → sides.

hepta-; → -gon.

Hermitian conjugate
  همیوغ ِ اِرمیتی   
hamyuq-e Hermiti

Fr.: conjugé hermitien   

Math.: The Hermitian conjugate of an m by n matrix A is the n by m matrix A* obtained from A by taking the → transpose and then taking the complex conjugate of each entry. Also called adjoint matrix, conjugate transpose. → Hermitian operator.

Hermitian, named in honor of the Fr. mathematician Charles Hermite (1822-1901), who made important contributions to number theory, quadratic forms, invariant theory, orthogonal polynomials, elliptic functions, and algebra. One of his students was Henri Poincaré; → conjugate.

hertz to meter conversion
  هاگرد ِ هرتز به متر   
hâgard-e hertz bé metr

Fr.: conversion hertz / mètre   

frequency to wavelength conversion.

hertz; → meter; → conversion.

HESS collaboration
  همکاری ِ HESS   
hamkâri-ye HESS

Fr.: collaboration HESS   

High Energy Stereoscopic System (H.E.S.S.).

H.E.S.S.; → collaboration.

hexagon
  شش‌بر، شش‌گوش   
šešbar (#), šešguš (#)

Fr.: hexagone   

A six-sided → polygon.

hexa-; → -gon;.

Hickson Compact Group (HCG)
  گروه ِ همپک ِ هیکسون   
goruh-e hampak-e Hickson

Fr.: groupe compact de Hickson   

A list of 100 compact groups of galaxies that were identified by a systematic search of the → Palomar Observatory Sky Survey red prints. Each group contains four or more galaxies, has an estimated mean surface brightness brighter than 26.0 magnitude per arcsec2 and satisfies an isolation criterion.

Hickson, Paul, 1982, ApJ 255, 382; → compact; → group.

hierarchical structure formation
  دیسش ِ ساختار ِ پایگانی   
diseš-e sâxtâr-e pâygâni

Fr.: formation de structures hiérarchiques   

A cosmological → structure formation model in which the smallest gravitationally bound structures (→ quasars and galaxies) form first, followed by → groups, → galaxy clusters, and → superclusters of galaxies.

hierarchical; → structure; → formation.

Higgs boson
  بوسون ِ هیگز   
boson-e Higgs (#)

Fr.: boson de Higgs   

A hypothetical, neutral → elementary particle which plays a key role in the → standard model of → particle physics. This massive particle, whose mass is estimated to be about 125 GeV (→ giga → electron-volts) and a zero → spin, carries the → Higgs field. In the current version of the → electroweak theory, → W boson and → Z boson and all the fundamental constituents (→ quarks and → leptons) get their masses by interacting with the Higgs boson. The Higgs boson is produced by the fusion of two → gluons via a triangular loop of virtual top quarks. In the decay process, a loop of virtual top quarks allows the Higgs boson to decay into two photons. The particle's discovery was announced by → CERN in July 2012.

Named after the Scottish physicist Peter Ware Higgs (1929-), one of the researchers who theorized the existence of this particle in 1964. In fact three groups of physicists almost simultaneously published their results on this subject: François Englert and Robert Brout in August 1964; Peter Higgs in October 1964; and Gerald Guralnik, Carl Hagen, and Tom Kibble in November 1964; → boson.

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