An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 70 Search : on-
non-relativistic electron
  الکترون ِ ناباز‌آنیگی‌مند   
elektron-e nâ-bâzânigi-mand

Fr.: électron non-relativiste   

An electron that does not experience relativistic effects since its velocity is very small compared to that of light.

non-relativistic; → electron.

non-relativistic mechanics
  مکانیک ِ ناباز‌آنیگی‌مند   
mekânik-e nâ-bâzânigi-mand

Fr.: mécanique non-relativiste   

Mechanics in which the masses under consideration move at speeds much slower than the speed of light.

non-relativistic; → mechanics.


Fr.: non thermique   

The nature of a → non-thermal radiation.

non-; → thermal.

non-thermal emission
  گسیل ِ ناگرمایی   
gosil- nâgarmâyi (#)

Fr.: émission non thermique   

non-thermal radiation.

non-thermal; → emission.

non-thermal filament (NTF)
  رشته‌ی ِ ناگرمایی   
rešte-ye nâgarmâyi

Fr.: filament non thermique   

Any of many long and slender structures visible in → radio continuum images of the inner hundred parsecs of the → Galactic Center. NTFs are typically tens of parsecs long and only a fraction of parsec wide. They may occur in isolation or in bundles, such as those comprising the linear portion of the prominent → radio Arc. Their → non-thermal spectrum and strong → linear polarization indicate → synchrotron radiation. The magnetic fields in the NTFs have been estimated from various means. Early estimates centered on the radio Arc, and focused on a comparison between the → magnetic pressure and the estimated → ram pressure from nearby → molecular cloud interactions, indicated magnetic field strengths as high as 1 mG (Morris and Yusef-Zadeh 1985). More recent observations, however, have pointed to significantly weaker magnetic fields among the population of NTFs. Synchrotron models of the radio spectrum imply equipartition magnetic fields between 50-200 μG. Theoretically, it has been challenging to understand the nature of these filaments that resemble extragalactic → radio jets but are not accompanied with any obvious source of acceleration of charged particles to high energy → relativistic energies. Although a number of detailed models have been considered, there is no consensus as to the origin of the NTFs. These models suggest that molecular and ionized gas clouds, mass-losing stars, → Galactic winds, magnetic activity of the → supermassive black hole at the Galactic center, and → lepton production due to → dark matter annihilation play a role in the processes that lead to the production of the NTFs (Linden et al. 2011, ApJ 741,95, and references therein). In most models, the magnetic field is strong and its global geometry in the central region of the Galaxy is considered to be → poloidal and static. However, some recent models have argued that the magnetic field is local and dynamic.

non-thermal; → filament.

non-thermal radiation
  تابش ِ ناگرمایی   
tâbeš-e nâgarmâyi (#)

Fr.: rayonnement non thermique   

The electromagnetic radiation whose characteristics do not depend on the temperature of the emitting source. In contrast to → thermal radiation, it has a different spectrum from that of → blackbody radiation. The three common types of non-thermal radiation in astronomy are: → synchrotron radiation, → bremsstrahlung radiation, and → maser  → stimulated emission.

non-thermal; → radiation.

non-thermal spectrum
  بیناب ِ ناگرمایی   
binâb-e nâgarmâyi

Fr.: spectre non thermique   

A radio emission with a negative → spectral index. In this type of emission the intensity of the emitted radiation increases with wavelength.

non-thermal; → spectrum.


Fr.: non zéro, non nul   

Not equal to zero.

non-; → zero.

non-zero polynomial
  بلنامین ِ نا-صفر   
bolnâmin-e nâ-sefr

Fr.: polynôme non nul   

A → polynomial that at least has one non-zero → coefficient. See also → zero polynomial.

non-zero; → polynomial.

bar- (#), dar- (#)

Fr.: sur   

Adverb, used as prefix denoting "in, into, onto; toward; with continuous activity," etc.

O.E. on, variant of an "in, on, into," from P.Gmc. (cf. Du. aan, Ger. an, Goth. ana "on, upon"), from PIE base *ano "on" (cf. Av. ana "on," Gk. ana "on, upon," L. an-, O.C.S. na, Lith. nuo "down from").

Bar "on; up; upon; in; into; at; forth; with; near; before; according to" (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").
Dar- "in," from Mid.Pers. andar, → intra-.


Fr.: en ligne   

The state when two or more devices are directly connected and are communicating efficiently.
Of computers, operating under the direct control of, or connected to, a main computer.

on; → line.

on-line reduction
  باز‌هازشِ بر-خط   
bâzhâzeš-e bar-xatt

Fr.: réduction enligne   

Preliminary reduction of observational data at a telescope simultaneously with their acquisition.

on-line; → reduction.

on-source observation
  نپاهشِ بر-خن   
nepâheš-e bar-xan

Fr.: observation sur la source   

In comparison with → off-source observation, an observation which is concerned with the source itself.

on-; → dource; → observation.

on-the-spot (OTS) approximation
  نزدینش ِ درجا   
nazdineš-e darjâ


An approximation in the treatment of photoionized → H II regions, whereby secondary ionizing photons are absorbed immediately very close to their site of emission. The secondary photons, produced by → radiative recombinations directly to the → ground states, are thus ignored with respect to the ionizing photons emitted by the → exciting star. The OTS approximation requires that the ionized gas be sufficiently dense so that secondary ionizing photons are very likely absorbed within the H II region.

on; → spot; → approximation.

Nazdineš, → approximation; dar "in," from Mid.Pers. andar, → intra-.

Orion-Cygnus Arm
  بازوی ِ شکارگر-ماکیان   
bâzu-ye šekârgar-mâkiyân

Fr.: bras Orion-Cygne   

Same as → Orion Arm.

Orion; → Cygnus; → arm.

photon-baryon plasma
  پلاسما فوتون-باریون   
plâsmâ foton-bâriyon

Fr.: plasma photon-baryon   

The plasma filling space before the → recombination epoch that mainly consisted of → cosmic microwave background radiation photons, electrons, protons, and → light elements.

photon; → baryon; → plasma.

principle of non-contradiction
  پروز ِ ناپادگویی   
parvaz-e nâpâdguyi

Fr.: principe de non-contradiction   

The third principle of → formal logic introduced in Aristotle's theory of the → syllogism: No statement can be both → true and → false at the same time. Also called → law of non-contradiction.

principle; → non-; → contradiction.

proton-proton chain
  زنجیره‌ی ِ پروتون-پروتون   
zanjire-ye proton-proton (#)

Fr.: chaîne proton-proton   

A series of → thermonuclear reactions, taking place mainly in → low-mass stars, such as the Sun, which transforms four hydrogen nuclei (protons) into one helium (4He) nucleus and thereby generates energy in the stellar core. First, two protons (1H) combine to form a → deuterium nucleus (2H) with the emission of a → positron (e+) and a → neutrino (ν): 1H + 1H → 2H + e+ + ν. The deuterium nucleus then rapidly captures another proton to form a helium-3 nucleus (3He), while emitting a → gamma ray (γ): 2H + 1H → 3He + γ. There are three alternatives for the next step. In the PP I chain, occurring in 86% of the cases, two 3He nuclei fuse to a final 4He nucleus while two protons are released: 3He + 3He → 4He + 1H + 1H. The mass of the resulting 4He nucleus is less than the total mass of the four original protons used to produce 4He (→ mass defect). The difference, ~ 0.7% of the total mass of the protons, is converted into energy and radiated by the Sun. In this process, the Sun loses some 4 million tons of its mass each second. See also → CNO cycle.

proton; → chain.

proton-proton reaction
  واژیرش ِ پروتون-پروتون   
vâžireš-e-e proton-proton

Fr.: réaction proton-proton   

A → thermonuclear reaction in which two protons collide at very high velocities and combine to form a → deuterium. See also → proton-proton chain.

proton; → reaction.

radiation-dominated Universe
  گیتی ِ تابش‌چیره   
giti-ye tâbeš-ciré

Fr.: Univers dominé par le rayonnement   

An early epoch in the history of the → Universe when the radiation → density parameter was Ωr≈ 1, while other density parameters had negligible contributions. A radiation-dominated Universe is characterized by R/R0 ∝ t1/2, where R is the → cosmic scale factor and t is time. According to the → Big Bang model, the radiation-dominated phase was followed by the → matter-dominated phase.

radiation; → dominate; → Universe.

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