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: 471 Search : ity
gravity wave
  موج ِ گرانی   
mowj-e gerâni

Fr.: onde de gravité   

1) A wave that forms and propagates at the free → surface of a body of → fluid after that surface has been disturbed and the fluid particles have been displaced from their original positions. The motion of such waves is controlled by the restoring force of gravity rather than by the surface tension of the fluid.
2) Not to be confounded with → gravitational wave.

gravity; → wave.

group velocity
  تندای ِ گروه   
tondâ-ye goruh

Fr.: vitesse de groupe   

The velocity at which the envelope of a → wave packet propagates, vgr = dω/dk, at k0 (the central value of k). The group velocity can be equal to, larger, or smaller than the → phase velocity.

group; → velocity.

H II region luminosity
  تابندگی ِ ناحیه‌ی ِ H II   
tâbandegi-ye nâhiye-ye H II

Fr.: luminosité de région H II   

The total number of → Lyman continuum photons emitted by an → H II region. It is usually derived using → radio continuum observations which are less affected by → interstellar extinction. The measured value is often a lower limit because of photon leakage from the H II region and absorption. See also → density-bounded H II region.

H II; → region; → luminosity.

heat capacity
  گنجایش ِ گرمایی   
gonjâyeš-e garmâyi (#)

Fr.: capacité thermique, ~ calorifique   

The ratio of an amount of heat, dQ, transferred to a body in some process to the corresponding change in the temperature of the body: C = dQ/dT. The heat capacity depends upon the mass of the body, its chemical composition, thermodynamic state, and the kind of process employed to transfer the heat. The word "capacity" may be misleading because it suggests the essentially meaningless statement "the amount of heat a body can hold," whereas what is meant is the heat added per unit temperature rise. → specific heat.

heat; → capacity.

helicity
  پیچاری   
picâri

Fr.: hélicité   

1) In particle physics, the projection of the spin of an elementary particle on the direction of momentum.
2) In fluid mechanics, → kinetic helicity.
3) In magnetohydrodynamics, → magnetic helicity.

From → helix + → -ity.

heredity
  ریگن‌داشت، ریگنداشت   
rigandâšt

Fr.: hérédité   

The passing on of physical or mental characteristics genetically from one generation to another (OxfordDictionaries.com).

M.E., from M.Fr. hérédité, from O.Fr. eredite "inheritance, legacy," from L. hereditatem (nominative hereditas) "heirship, inheritance," → heritage.

Rigandâšt, literally "possessing heritage," from rigan, → heritage, + dâšt past stem of dâštan "to have, hold, possess, maintain," → property.

heterogeneity
  دگرگنی   
degargeni

Fr.: hétérogénéité   

The quality or state of being → heterogeneous. See also → homogeneity, → inhomogeneity.

Noun from → heterogeneous.

High Accuracy Radial velocity Planet Searcher (HARPS)
  هارپس   
HARPS

Fr.: HARPS   

A high-precision echelle spectrograph built for exoplanet findings and installed on the ESO's 3.6m telescope at La Silla Observatory in Chile. The first light was achieved in February 2003. HARPS has discovered dozens of exoplanets, making it the most successful planet finder behind the Kepler space observatory. HARPS can detect movements as small as 0.97 m s-1 (3.5 km h-1), with an effective precision of the order of 30 cm s-1, and a → resolving power of 120,000 (Mayor et al., 2003, ESO Messengar 114, 20).

high; → accuracy; → radial; → velocity; → planet; → search; → -er.

high-velocity clouds (HVCs)
  ابرهای ِ تندرو   
abrhâ-ye tondrow

Fr.: nuages à grande vitesse   

A population of neutral or partly ionized gas clouds in the → Galactic halo which are seen as high-altitude structures in the → atomic hydrogen  → 21 cm emission at high radial velocities (vLSR > 100 km/sec). They have substantial neutral → column densities (> 1019 cm-2) and their → metallicities range from 0.1 to about 1.0 times solar. The distances to the majority of them remain unknown. They may represent the continuing infall of matter onto the → Local Group. See also → compact high-velocity clouds.

high; → velocity; → cloud.

Hill stability
  پایداری ِ هیل   
pâydâri-ye Hill

Fr.: stabilité de Hill   

The condition for the stability of a → three-body system. Three-body systems exist widely in the → solar system and → extrasolar systems, including Sun-planet-moon systems, planets-star systems, and → triple star systems. This concept of stability was introduced by Hill (1878). He used the → Jacobi integral to construct bounds of motion for → conservative systems with time-independent → potentials, which was introduced to study the stability of the Moon in the Sun-Earth → restricted three-body problem. The stability is defined by the → zero-velocity surface based on the Jacobi integral. The concept of the Hill stability has been used by many researchers to study the stability of three-body systems. The studies include the Hill stability in the full → three-body problems, the hierarchical three body problems, and the restricted three body problems (See, e.g., S. Gong & J. Li, 2015, Astrophys Space Sci. 358,37).

Hill, G.W.: Researches in the lunar theory. Am. J. Math. 1(2), 129-147 (1878); → stability.

homogeneity
  همگنی   
hamgeni (#)

Fr.: homogénéité   

State or quality of having a uniform appearance or composition, being homogeneous

homogeneous + → -ity.

humanity
  ۱) مرتوگان؛ ۲) مرتوگانی   
1) martugân; 2) martugâni

Fr.: humanité   

1) All human beings collectively; the human race; humankind.
2) The quality of being human; human nature.

human + → -ity.

humidity
  نم   
nam (#)

Fr.: humidité   

Generally, a measure of the water vapor content of the air. Popularly, it is used synonymously with → relative humidity. → absolute humidity, → dew point, → mixing ratio, → specific humidity.

Humidity, from O.Fr. humide, from L. humidus "moist, wet," variant (by influence of humus "earth") of umidus, from umere "be moist."

Nam "humidity, moisture," from Mid.Pers. nam, namb "moisture;" Av. napta- "moist," nabās-câ- "cloud," nabah- "sky;" cf. Skt. nábhas- "moisture, cloud, mist;" Gk. nephos "cloud, mass of clouds," nephele "cloud;" L. nebula "mist," nimbus "rainstorm, rain cloud;" O.H.G. nebul; Ger. Nebel "fog;" O.E. nifol "dark;" from PIE *nebh- "cloud, vapor, fog, moist, sky."

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.

identity
  ایدانی، این‌همانی، کیستی، چیستی   
idâni, inhamâni (#), kisti (#), cisti (#)

Fr.: identité   

1) Math.: An equation that is valid for all values of its variables. A mathematical relationship equating one quantity to another.
2) Logic: An assertion that two terms refer to the same thing.
3) Psychology: The character of persisting unchanged. The feeling that one knows who one really is.

From M.Fr. identité, from L.L. identitas "sameness," from ident-, combining form of L. idem "the same; at the same time; also; moreover," from id "it, that one" + demonstrative suffix -dem + -itas a suffix used to form abstract nouns expressing state or condition.

Idâni, from iduni, from Mid.Pers. êdônih "being this, being that, being so, the manner of being," from êdôn "thus, so," Mod.Pers. idun "this, in this manner, now;" O.Pers. aita- demonstrative pronoun "this;" Av. aēta- "this; this here; this now," aētaδ- (adv.) "here, there; then, thus; thereupon;" cf. Skt. etad "this," iti "thus, in this manner;" akin to L. idem, as above.

identity axiom
  بنداشت ِ ایدانی   
bondâšt-e idâni

Fr.: axiome d'identité   

A basic rule in → group theory stating that there exists a unit group element e, called the identity, such that for any element a of the group a * e = e * a = a.

identity; → axiom.

identity element
  بن‌پار ِ ایدانی   
bonpâr-e idâni

Fr.: élément neutre   

In a mathematical system, an element which leaves unchanged any other element on which it operates. Thus 0 is the identity element for addition: a + 0 = a. And 1 is the identity element for multiplication: a . 1 = a.

identity; → element.

identity function
  کریای ِ ایدانی   
karyâ-ye idâni

Fr.: fonction d'identité   

Math.: Any function f for which f(x) = x for all x in the domain of definition.

identity; → function.

identity matrix
  ماتریس ِ ایدانی   
mâtris-e idâni

Fr.: matrice identité   

In linear algebra, the simplest nontrivial diagonal matrix, an n-by-n square matrix with ones on the main diagonal and zeros elsewhere.

identity; → matrix.

identity operator
  آپارگر ِ ایدانی   
âpârgar-e idâni

Fr.: opérateur d'identité   

An operator which takes a real number to the same real number.

identity; → operator.

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