An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 712
  مول، ملکول-گرم، اتم-گرم   
mol, molekul-geram, atom-geram

Fr.: mole   

The → SI unit of amount of → substance; symbol mol. One mole contains exactly 6.022 140 76 × 1023 elementary entities. This number is the fixed numerical value of the → Avogadro constant, NA, when expressed in the unit mol-1.

From Ger. Mole, short for Molekül, from Fr. → molecule.

molekuli (#)

Fr.: moléculaire   

Of or pertaining to or caused by molecules.

From → molecule + -ar variant of the adjective-forming suffix → -al, joined to words in which an l precedes the suffix.

Molekuli, from molekulmolecule + -i adj. suffix.

molecular band
  باند ِ مولکولی   
bând-e molekuli (#)

Fr.: bande moléculaire   

A band of molecular origin present in a spectrum. See for example → cyanogen band, → S star.

molecular; → band.

molecular cloud
  ابر ِ مولکولی   
abr-e molekuli (#)

Fr.: nuage moléculaire   

A relatively dense, cold region of interstellar matter where the atoms are primarily bound together as molecules rather than free atoms or ionized particles. Molecular clouds represent the coldest and densest phase of the → interstellar medium. They consist primarily of → molecular hydrogen (H2), with temperatures in the range 10-100 K. Molecular hydrogen is not directly observable under most conditions in molecular clouds. Therefore, almost all current knowledge about the properties of molecular clouds has been deduced from observations of molecules such as → carbon monoxide (CO), which have strong emission lines mainly in the → millimeter portion of the → electromagnetic spectrum. So far 129 molecular species have been detected in molecular clouds, among which complex organic molecules. → Dust grains in molecular clouds play a crucial role in the formation of molecules. Molecular clouds are the principal sites where stars form. → giant molecular cloud; → Orion molecular cloud.

molecular; → cloud.

molecular clump
  گوده‌ی ِ مولکولی   
gude-ye molekuli

Fr.: grumeau moléculaire   

One of many compact and dense sub-structures in a → molecular cloud. Their typical sizes are about 0.5-10 → parsecs and their masses range from about 50 to 103 → solar masses. The gas temperatures are about 10-20 K, and the number densities from about 103 to 104 cm-3.

molecular; → clump.

molecular emission
  گسیل ِ مولکولی   
gosil-e molekuli

Fr.: émission moléculaire   

An → electromagnetic radiation emitted by → interstellar molecules through → transitions between → energy states of → molecules.

molecular; → emission.

molecular formula
  دیسول ِ مولکولی   
disul-e molekuli

Fr.: formule moléculaire   

The formula of a chemical compound, showing the kind and arrangement of atoms.

molecular; → formula.

molecular hydrogen
  هیدروژن ِ مولکولی   
hdirožen-e molekuli (#)

Fr.: hydrogène moléculaire   

A molecule consisting of two hydrogen atoms (H2) which is the most abundant molecule in the Universe. Molecular hydrogen plays a fundamental role in many astrophysical contexts. It is found in all regions where → self-shielding against the ultraviolet photons, responsible for its → photodissociation, is sufficiently large. Containing two identical hydrogen atoms, H2 is highly symmetric. Due to this property, the molecule has no → dipole moment and all → rotation-vibrational transitions within the electronic → ground state are → quadrupolar with low → spontaneous emission  → Einstein coefficient values. The molecule exists in two almost independent states, namely → orthohydrogen and → parahydrogen. H2 may be excited through several mechanisms, including: 1) → far ultraviolet (FUV) induced → optical pumping and → collisional excitation in → photodissociation regions (PDRs) associated with → star formation; 2) → hard X-rays penetrating and heating regions within → molecular clouds, which in turn excite H2 via collisions with electrons or hydrogen atoms; and 3) collisional excitation of H2 due to acceleration produced by interstellar → shock waves. H2 is thought to be chiefly produced via surface reactions on → interstellar grains, but the exact formation mechanism is not fully understood.

molecular; → hydrogen.

molecular outflow
  اُستچان ِ مولکولی   
ostacân-e molekuli

Fr.: flot moléculaire   

An outflow of molecular material, often → bipolar, observed in the regions of → star formation. Molecular outflows are thought to be driven by → bipolar jets from → protostars. They are probably → bow shocks which have had time to cool and be observable in molecular lines. Molecular outflows are poorly → collimated compared to the jets and tend to be slow moving (velocities 10-20 km s-1). Some bipolar outflows may be driven by → stellar winds.

molecular; → outflow.

molecular polarizability
  قطبش‌پذیری ِ مولکولی   
qotbeš-paziri molekuli

Fr.: polarisabilité moléculaire   

The ability of a molecular entity to be distorted from its normal shape by an external → electric field. When a molecule is subjected to an electric field there is a small displacement of electrical centers which induces a dipole in the molecule. More specifically, the molecular polarizability α is defined as the ratio of the induced → dipole moment (p) to the local electric field (E) that produces this dipole moment: α = p/E (in cgse units).

molecular; → polaizable; → -ity.

molecular proposition
  گزاره‌ی ِ مولکولی   
gozâre-ye molekuli

Fr.: proposition moléculaire   

In → propositional logic, a → sentence containing at least one → connectives. See also → atomic proposition.

atomic; → proposition.

molecular vibration
  شیوش ِ مولکولی   
šiveš-e molekuli

Fr.: vibration moléculaire   

The dynamical motion of chemically bound atoms which constantly change their position with each other. The vibration of molecules is treated within → quantum theory. Therefore, the energy of molecular vibration can only take → discrete values. To a first approximation, molecular vibrations can be approximated as → simple harmonic oscillator assigned to each mode.

molecular; → vibration.

molecular weight
  وزن ِ مولکولی   
vazn-e molekuli (#)

Fr.: poids moléculaire   

The sum of the atomic weights of all the atoms in a molecule.

molecular; → weight.

molekul (#)

Fr.: molécule   

The smallest unit of a chemical compound. A molecule consist of two or more atoms held together by covalent bonds.

From Fr. moléclue, from Mod.L.molecula, diminutive of L. moles "mass, massive structure, barrier;" → -ula


Fr.: MOLsphère   

A hypothetical, large molecular sphere, as a component of the → stellar atmosphere, suggested to encompass → red giant and → supergiant stars. This suggestion has offered satisfactory explanations to the spectrum of → Mu Cephei (Tsuji 2003), but it is not clear whether MOLspheres are common features of the atmospheres of all such stars.

MOL, from → molecular; → sphere.

  ۱، ۲) گشتاور؛ ۳) دم   
1, 2) gaštâvar (#); 3) dam (#)

Fr.: moment   

1) Physics: An expression involving the → product a → quantity, such as → force or → mass, and its perpendicular → distance from a reference point, such as → moment of force (or → torque), → moment of inertia, → moment of momentum.
2) Statistics: For a → random variable X, its nth moment about the mean is the expected value of the nth power of X, where n is a positive integer. The nth moment of the deviation of X from the mean is called the nth central moment. The first moment is the → mean, the second central moment is the → variance.
3) A short indefinite period of time.

From O.Fr. moment, from L. momentum "movement, moving power," also "instant, importance," contraction of *movimentum, from movere, → move.

Gaštâvar literally "that which makes turn, turning agent," from gašt "turning," past stem of gaštan, gardidan "to turn, to change" (Mid.Pers. vartitan; Av. varət- "to turn, revolve;" Skt. vrt- "to turn, roll," vartate "it turns round, rolls;" L. vertere "to turn;" O.H.G. werden "to become;" PIE base *wer- "to turn, bend") + âvar agent noun of âvardan "to bring; to cause, produce" (Mid.Pers. âwurtan, âvaritan; Av. ābar- "to bring; to possess," from prefix ā- + Av./O.Pers. bar- "to bear, carry," bareθre "to bear (infinitive)," bareθri "a female that bears (children), a mother;" Mod.Pers. bordan "to carry;" Skt. bharati "he carries;" Gk. pherein; L. fero "to carry").
Dam, "breath; moment; time," from Mod./Mid.Pers. damidan "to breathe, blow;" Av. dāδmainya- "blowing up," Skt. dahm- "to blow," dhámati "blows," Gk. themeros "austere, dark-looking," Lith. dumti "to blow," PIE dhem-/dhemə- "to smoke, to blow".

moment of force
gaštâvar (#)

Fr.: moment, couple   

A measure of a force's tendency to cause a body to → rotate about a specified → axis. It is given by the force times the perpendicular → distance of the → line of action from the axis. Same as → torque

moment; → force.

moment of inertia
  گشتاور ِ لختی   
gaštâvar-e laxti (#)

Fr.: moment d'inertie   

A quantity which is a measure of the inertness of a body in rotatory motion about an axis. It is equal to the sum of the products of the masses of all particles of the body by the squares of their distances from this axis: I = Σmiri2, where ri is the distance of the particle of mass mi from the axis. Moment of inertia depends only upon the shape of the body and the arrangement of its mass with respect to the axis. For a solid sphere it is (2/5)MR2. Moment of inertia is used in place of mass in problems involving rotation. Thus, the → angular momentum is Iω and → angular kinetic energy is (1/2)Iω2, where ω is → angular velocity.

moment; → inertia.

moment of momentum
  گشتاور ِ جنباک   
gaštâvar-e jonbâk

Fr.: moment cinétique   

Same as → angular momentum.

moment; → momentum.


Fr.: quantité de movement   

In → Newtonian mechanics, the momentum p of a body with → mass m and → velocity v is the product of these two quantities: p = mv. Momentum usually means → linear momentum as opposed to → angular momentum.

From L. momentum "movement, moving power," from movere "to move," → move.

Jonbâk, from jonb present stem of jonbidan "to move" (Mid.Pers. jumbidan, jumb- "to move," Lori, Laki jem "motion," related to gâm "step, pace;" O.Pers. gam- "to come; to go," Av. gam- "to come; to go," jamaiti "goes," gāman- "step, pac;" Mod.Pers. âmadan "to come;" Skt. gamati "goes;" Gk. bainein "to go, walk, step," L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE root *gwem- "to go, come") + -âk noun suffix.

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