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: 3079 Search : on
Central Molecular Zone (CMZ)
  زنار ِ مولکولی ِ مرکزی   
zonâr-e molekuli-ye markazi

Fr.: zone moléculaire centrale   

A vast, turbulent region encircling the → Milky Way's nucleus that contains a large fraction of the → Galaxy's dense → molecular clouds and → star formation regions. Spanning -1 to +1.5 degrees of → Sgr A*, the CMZ is about 400 pc × 100 pc in size and contains at least 107solar masses of → giant molecular clouds, approximately 10% of the Galaxy's molecular gas. The gas in the CMZ is at higher temperature than typical giant molecular clouds and has high velocity dispersion reflecting the → turbulent nature of the gas in the area. Despite these extensive molecular reserves, the → star formation rate within the CMZ is actually lower than expected based on the analysis of nearby → star-forming regions in the quiescent → Galactic disk. A common assumption is that this is a result of the extreme conditions within the CMZ, where the density, pressure, temperature, → velocity dispersion and → radiation field are all significantly greater than elsewhere in the Milky Way (Clark et al. 2018, The Messenger 173, 22 and references therein).

central; → molecular; → zone.

centrifugal acceleration
  شتاب ِ مرکزگریز   
šetâb-e markaz-goriz (#)

Fr.: accélération centrifuge   

Of a point rotating in a circle round a central point, the outward acceleration away from the rotation axis. It corresponds to → centrifugal force. The centrifugal acceleration is given by ω x ω x r, or v2/r, where ω is → angular velocity, r the distance to the rotating axis, and v the → tangential velocity. The centrifugal and → centripetal accelerations are equal and opposite.

centrifugal; → acceleration.

centripetal acceleration
  شتاب ِ مرکزگرا   
šetâb-e markaz-gerâ (#)

Fr.: accélération centripète   

The rate of change of the → tangential velocity of a body moving along a circular path. The direction of centripetal acceleration is always inward along the → radius vector of the → circular motion. The magnitude of the centripetal acceleration is related to the → tangential velocity (v) and → angular velocity (ω) as follows: ac = v2/r = rω2. According to → Newton's second law, an object undergoing centripetal acceleration is experiencing a → centripetal force.

centripetal; → acceleration.

chain reaction
  واژیرش ِ زنجیری، واکنش ِ ~   
vâžireš-e zanjiri, vâkoneš-e ~

Fr.: réaction en chaîne   

A succession of → nuclear fissions when the neutrons released by previous fissions produce other nuclear fissions which themselves cause other reactions and the reactions goes on increasing exponentially.

chain; → reaction.

Chamaeleon
  آفتاب‌پرست   
Âftâbparast (#)

Fr.: Caméléon   

The Chameleon. A small inconspicuous → constellation in the southern hemisphere near → Crux, lying at approximate position: R.A. 11 h, Dec. -80°. Abbreviation: Cha; genitive form: Chamaeleonis;

From O.Fr. chaméléon, from L. chamaeleon, from Gk. khamaileon, from khamai "on the ground" (akin to chthon "earth;" cf. Av. zam- "the earth," Mid.Pers. zamig, Mod.Pers. zami, zamin "the earth," Skt. ksam, L. homo "earthly being" and humus "the earth," PIE *dh(e)ghom "earth") + leon "lion."

Âftâbparast "chameleon," literally "sun adorer," from âftâb "Sun, sunlight" + parast "worshipper,"

characteristic equation
  هموگش ِ سرشتاری   
hamugeš-e sereštâri

Fr.: équation caractéristique   

Physics: An analytical relationship between a set of physical variables that determines the state of a physical system.
Math.: The equation which is solved to find a matrix's eigenvalues, also called the characteristic polynomial.

characteristic; → equation.

characterization
  ۱) سرشتارش؛ ۲) تنومسا سازی   
1) sereštâreš 2) tanumsâ sâzi

Fr.: 1) caractérisation; 2) représentation des caractères   

1) The act of describing the character or qualities of someone or something.
2) The artistic representation (as in fiction or drama) of human character or motives (Merriam-Webster.com).

characterize; → -tion.

charge conjugation
  همیوغش ِ بار   
hamyuqeš-e bâr (#)

Fr.: conjugaison de charges   

In particle physics, an operation that changes a particle to its antiparticle in equations describing subatomic particles or, equivalently, reverses its charge and magnetic moment.

charge; → conjugation.

charge distribution
  واباژش ِ بار   
vâbâžeš-e bâr

Fr.: distribution des charges   

The way a number of → electric charges are arranged in space with respect to the point of observation.

charge; → distribution.

charge-injection device (CID)
  دستگاه ِ درشانش ِ بار   
dastrgâh-e daršâneš-e bâr

Fr.: dispositif à injection de charge   

A charge-transfer device that passes along stored charges positioned at predetermined locations; it is used as an image sensor in which the image points are accessed by reference to their horizontal and vertical coordinates.

charge; → injection; → device.

Charon
  خارون   
Xâron (#)

Fr.: Charon   

The largest satellite of Pluto. It is about 1,040 km across, roughly half Pluto's diameter. Charon is unusual in that it is the largest moon with respect to its primary planet in the Solar System. Moreover, the Pluto-Charon system is extraordinary because the center of mass lies in open space between the two, a characteristic of a double planet system. Pluto and Charon are also tidally locked in a synchronous orbit. Pluto's rotational period is 6.39 Earth days. It takes 6.39 days for Charon to make one revolution around Pluto. Thus, the two bodies continuously face each other. Also called Pluto I.

In Gk. mythology, Xαρον (Charon) was a figure who ferried the dead across the river Styx into Hades (the underworld).

chemical adsorption
  برشم ِ شیمیایی   
baršam-e šimiyâyi

Fr.: adsorption chimique   

Same as → chemisorption.

chemical; → adsorption.

chemical bond
  بند ِ شیمیک، ~ شیمیایی   
band-e šimik, ~ šimiyâyi

Fr.: liaison chimique   

A force by which chemical substances are held together by attraction of atoms to each other through sharing, as well as exchanging, of electrons.

chemical; → bond.

chemical composition
  همنهش ِ شیمیک   
hamneheš-e šimik

Fr.: composition chimique   

The identities, and relative abundances of the → chemical elements or → compounds that make up a substance.

chemical; → composition.

chemical equation
  هموگش ِ شیمیایی   
hamugeš-e šimiyâyi

Fr.: équation chimique   

The symbolic representation of a chemical reaction where the formulae of the → reactants are placed on the left and the formulae of → products on the right of an arrow.

chemical; → equation.

chemical evolution
  فرگشت ِ شیمیایی   
fargašt-e šimiyâyi (#)

Fr.: évolution chimique   

A cumulative change in the chemical properties, or more specifically, the relative abundances of chemical elements in an astrophysical system.

chemical; → evolution.

chemical reaction
  واژیرش ِ شیمیایی، واکنش ِ ~   
vâžireš-e šimiyâyi, vâkoneš-e ~

Fr.: réaction chimique   

A → change or → transformation in which a → substance → decomposes, → combines with other → substances, or interchanges constituents with other substances.

chemical; → reaction.

chemical separation
  جدایی ِ شیمیایی   
jodâyi-ye šimiyâyi

Fr.: séparation chimique   

The physical processes that can cause certain elements to migrate in a → stellar atmosphere. These processes are thought to be important in creating the chemical peculiarities seen in → Am stars and → Ap stars.

chemical; → separation.

chemisorption
  شیمی‌شمش   
šimi-šameš

Fr.: chimisorption   

A kind of → adsorption in which the forces involved are → valence forces of the same kind as those operating in the formation of → chemical compounds. Same as → chemical adsorption. See also → physisorption.

Chemi-, from → chemical; → sorption.

Cherenkov radiation
  تابش ِ چرنکوف   
tâbeš-e Čerenkov (#)

rayonnement de Čerenkov   

Visible radiation emitted when → charged particles pass through a transparent medium faster than the speed of light in that medium.

Named after Pavel A. Čerenkov (1904-1990), Russian physicist, who discovered the phenomenon. He shared the Nobel prize 1958 in physics with Ilya Frank and Igor Tamm, who in 1937 gave the theoretical explanation for this radiation.

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