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: 309 Search : act
Imaging Atmospheric Cherenkov Technique (IACT)
  تشنیک ِ تصویرگری ِ چرنکوف ِ جوی   
tašnik-e tasvirgiri-ye Čerenkov-e javvi

Fr.: téchnique d'imagerie Čerenkov atmosphérique   

The method used to detect very brief flashes of → Cherenkov radiation generated by the → cascade shower of → relativistic charged particles produced when a very high-energy → gamma ray (in the range 50 GeV to 50 TeV) strikes the atmosphere at a typical altitude of 10 km. Owing to this technique, it possible to discriminate cosmic gamma rays from the cosmic ray background and to determine their energy and source direction. More specifically, the incoming gamma-ray photon undergoes → pair production in the vicinity of the nucleus of an atmospheric molecule. The electron-positron pairs produced are of extremely high energy and immediately radiate in a → bremsstrahlung process. This radiation is itself extremely energetic, with many of the photons undergoing further pair production. A cascade of charged particles ensues which, due to its extreme energy, produces a flash of Cherenkov radiation lasting between 5 and 20 nano-seconds. The total area on the ground illuminated by this flash corresponds to many hundreds of square meters, which is why the effective area of IACT telescopes should be large.

imaging; → atmospheric; → Cherenkov; → technique.

impact
  برخورد   
barxord (#)

Fr.: impact, collision   

A collision between two bodies. In the case of solar system objects, when one is much smaller than the other (like a meteoroid colliding with the Earth), a crater may be produced on the larger body.

From L. impactus, p.p. of impingere "to drive into, strike against," from → in- "in" + pangere "to fix, fasten."

Barxord, verbal noun of barxordan "to collide, clash, dash against each other," from bar- "on, upon, up" (Mid.Pers. abar; O.Pers. upariy "above; over, upon, according to;" Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + xordan "to hit, strike," originally "to eat, drink, devour," and by extension "to destroy," from Mid.Pers. xvardan "to eat, enjoy (food)," Av. xvar- "to consume, eat;" Laki dialect hovârden "to eat;" Proto-Iranian *huar- "to consume, eat."

impact crater
  لاوک ِ برخورد   
lâvak-e barxord

Fr.: cratère d'impact   

A depression produced by the collision of a meteorite, asteroid, or comet with the surface of a planet or a satellite. Impact craters are the most characteristic surface features of solar system rigid bodies. They range in size up to hundreds or thousands of kilometers (where the impacts create giant basins as on the Moon, Mars, and Mercury).

impact; → crater.

impact event
  رویداد ِ برخورد   
ruydâd-e barxord

Fr.: impact cosmique   

A collision between two celestial objects, specially solar system bodies, with considerable consequences. Impact events involve release of large amounts of energy. Some examples are the 1908 Siberian → Tunguska event by a → comet, the → Barringer Crater, and the collision of an → asteroid with Earth 65 million years ago, which is thought to have led to the extinction of the dinosaurs and other species of the → Cretaceous-Paleogene period.

impact; → event.

impact hazard
  آپه‌ی ِ برخورد   
âpe-ye barxord

Fr.: risque d'impact   

The danger of collision with Earth posed by solar system small bodies that pass near our planet. These objects include → near-Earth asteroids and nuclei of → comets. See also: → near-Earth object, → impact crater, → Torino scale, → Palermo scale, → Space Situational Awareness.

impact; → hazard.

impact ionization
  یونش ِ برخوردی   
yoneš-e barxordi

Fr.: ionisation par collision   

The loss of orbital electrons by an atom of a crystal lattice which has undergone a high-energy collision.

impact; → ionization.

impact parameter
  پارامون ِ برخورد   
pârâmun-e barxord

Fr.: paramètre d'impact   

1) A measure of the distance by which a collision fails being frontal.
2) In → gravitational lensing, the distance of closest approach of the light path to the → lensing object.
3) In → rainbows, the displacement of the → incident from an axis that passes through the center of the water droplet.

impact; → parameter

impact winter
  زمستان ِ برخورد   
zemestân-e barxord

Fr.: hiver par impact   

The enormous drop in temperature and the related effects of the shrouding of Earth with soot and dust particles after the planet is struck by a sizable comet or asteroid. Such a phenomenon is believed to have killed off the dinosaurs 65 million years ago.

impact; → winter.

impactite
     
impaktit, barxordit

Fr.: impactite   

A general term used for all rocks affected by, or produced by, the → shock waves and other processes generated by hypervelocity → meteorite → impact events. Impactites occur in and around the → impact crater, typically as individual bodies composed of mixtures of melt and rock fragments, often with traces of meteoritic material.

impact; → -ite.

impactor
  برخوردگر   
barxordgar

Fr.: impacteur   

A natural impacting body, such as a comet, asteroid, or planet. It can also be a space probe designed to collide with an astronomical body in the solar system.

Impactor, from → impact + -or a suffix forming agent nouns.

Barxordgar, from barxord, → impact, + -gar agent suffix, from kar-, kardan "to do, to make" (Mid.Pers. kardan, O.Pers./Av. kar- "to do, make, build," Av. kərənaoiti "makes," cf. Skt. kr- "to do, to make," krnoti "makes," karma "act, deed;" PIE base kwer- "to do, to make").

inactive
  ناژیرا   
nâžirâ

Fr.: inactif   

1) Not → active.
2) Chem.: Not → reactive.

in-; → active.

index of refraction
  دیشن ِ شکست   
disšan-e šekast

Fr.: indice de réfraction   

Same as → refractive index.

index; → refraction.

integrating factor
  کروند ِ درستالنده   
karvand-e dorostâlandé

Fr.: facteur intégrant   

A function that converts a → differential equation, which is not exact, into an → exact differential equation. This is done by multiplying all terms of the original equation by the integrating factor.

integrate; → factor.

interact
  اندرژیریدن   
andaržiridan

Fr.: interagir   

To act upon one another; have a mutual or reciprocal action.

Interact, from → inter- + → act.

interacting binary
  دورین ِ اندرژیرنده   
dorin-e andaržirandé

Fr.: binaire en interaction   

A binary star system in which mass transfer between the components takes place. → contact binary; → Roche lobe.

Interacting, adj. of → interact; → binary.

interacting galaxies
  کهکشان‌های ِ اندرژیرنده   
kahkešânhâ-ye andaržandé

Fr.: galaxies en interaction   

Galaxies that are close enough for their mutual gravitational attraction to produce perturbed shapes or extruded filaments of stellar material, called → tidal tails. Most galaxies are in clusters, and gravitational interactions between them are common.

Interacting, adj. of → interact; → galaxy.

interaction
  اندرژیرش   
andaržireš

Fr.: interaction   

General: Mutual or reciprocal action or influence.
Physics: 1) What happens between a system and its surroundings when an observable change in one corresponds to or correlates with an observable change in the other.
2) The natural phenomenon of the transfer of energy between two particles. The four known kinds of interactions, in the order of increasing strength, are: → gravitational, → weak, → electromagnetic, and → strong.

Interaction, from → inter-; + → action.

interactional
  اندرژیرشی   
andaržireši

Fr.:   

Capable of acting on or influencing each other

From → interaction; + → -al.

interactive
  اندرژیری   
andaržiri

Fr.: interactif   

1) Acting one upon or with the other.
2) Computers: Of or pertaining to a system or program that maintains an exchange with the user, alternately accepting input and then responding.

inter-; → active.

intergalactic
  اندرکهکشانی   
andarkahkešâni

Fr.: intergalactique   

Of, existing, or occurring in the space between galaxies. → intergalactic absorption, → intergalactic cloud, → intergalactic matter , → intergalactic medium , → warm-hot intergalactic medium.

inter-; → galactic.

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