An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 471 Search : ity

Fr.: mentalité   

1) Mental capacity or endowment.
2) Mental capacity or endowment (

mental; → -ity.


Fr.: métallicité   

In a star, nebula, or galaxy, the proportion of the material that is made up of → metals, that is elements heavier than → helium. It is generally denoted by Z. The term "metallicity" is a misnomer used in astrophysics.
1) In practice, the metallicity of stars is usually expressed by the number ratio of → iron atoms to → hydrogen atoms per unit volume, with respect to the solar values: [Fe/H] = log10(NFe/NH)star - log10(NFe/NH)Sun, where NFe and NH are the numbers of iron and hydrogen atoms per unit volume. In fact it is taken to be equal to the iron → abundance with respect to the solar value. The solar logarithmic iron abundance is 7.50 ± 0.04 (Asplund et al. 2009, ARAA 47, 481), with respect to that of hydrogen which, by convention, is 12.00. Stellar metallicity is often expressed in mass fraction. See also → solar metallicity.
2) Nebular metallicity is often defined as the relative abundance of → oxygen: (NO/NH)neb/(NO/NH)Sun, where NO and NH represent the numbers of oxygen and hydrogen atoms per unit volume.

From metallic, from → metal + → -ity.

metallicity distribution function (MDF)
  کریای ِ واباژش ِ فلزیگی   
karyâ-ye vâbâžeš-e felezigi

Fr.: fonction de distribution de métallicité   

A plot representing the number of stars (or systems) per metallicity interval, usually expressed in [Fe/H] (abundance of → iron relative to → hydrogen).

metallicity; → distribution; → function.

metallicity gradient
  زینه‌ی ِ فلزیگی   
zine-ye felezigi

Fr.: gradient de métallicité   

The decrease in the → abundances of → heavy elements in a → disk galaxy as a function of distance from the center. Radial metallicity gradients are observed in many galaxies, including the → Milky Way and other galaxies of the → Local Group. In the case of the Milky Way, several objects can be used to determine the gradients: → H II regions, → B stars, → Cepheids, → open clusters, and → planetary nebulae. The main diagnostic elements are oxygen, sulphur, neon, and argon in photoionized nebulae, and iron and other elements in Cepheids, open clusters, and stars. Cepheids are probably the most accurate indicators of abundance gradients in the Milky Way. They are bright enough to be observed at large distances, so that accurate distances and spectroscopic abundances of several elements can be obtained. Average abundance gradients are generally between -0.03 → dex/kpc and -0.10 dex/kpc, with a a flattening out of the gradients at large galactocentric distances (≥ 10 kpc). The existence of these gradients offers the opportunity to test models of → chemical evolution of galaxies and stellar → nucleosynthesis.

metallicity; → gradient.


Fr.: microgravité   

The state or condition where the force of → gravity is very weak, e.g. the → weightlessness experienced inside an orbiting spacecraft.

micro-; → gravity.

kehini (#)

Fr.: minorant   

The smaller number, part, or quantity of a whole.

minor; → -ity.

  مدیگی، مدمندی   
modigi, modmandi

Fr.: modalité   

The quality or state of being → modal.

modal; → -ity.

novini (#)

Fr.: modernité   

1) The quality of being → modern.
2) A rather diffuse term with many meanings depending on the disciplinary context. Generally, modernity refers to the cultural, intellectual, and economic consequences of the → Enlightenment and the epoch with which they are associated. Modernity is the end result of the → modernization process.

modern + → -ity.

modulus of rigidity
  پیمون ِ سخت‌پایی   
peymun-e saxtpâyi

Fr.: module de rigidité   

Same as → shear modulus.

modulus; → rigidity.

molar heat capacity
  گنجایش ِ گرمایی ِ مولی   
gonjâyeš-e garmâyi-ye moli

Fr.: capacité thermique molaire   

The → heat capacity of one → mole of substance: Cμ = μ C, where μ is the → molecular weight and C the → specific heat capacity. The molar heat capacity of water is practically 18 cal/mole.C°.

Molar, adj. of → mole; → heat; → capacity.

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.

monochromatic opacity
  کدری ِ تکفام   
kederi-ye takfâm

Fr.: opacité monochromatique   

The sum of → absorption coefficientν) and → scattering coefficientν) at a given frequency: kν = κν + σν. See also the → Rosseland mean opacity.

monochromatic; → opacity.

morphology-density relation
  بازانش ِ ریخت-چگالی   
bâzâneš-e rixt-cagâli

Fr.: relation morphologie-densité   

An observationally determined relationship between the → morphological classification of galaxies and the → environments in which they are located. Specifically, the morphology-density relation indicates that early-type galaxies (→ ETG) are preferentially located in high density environments, whereas late-type galaxies (→ LTG) are preferentially found in low density environments. Hence, spiral galaxies are rare in the high densities of clusters and are common in the lower density group environments. Early-type galaxies, on the other hand, are common in clusters and are rarely found in isolation.

morphology; → density; → relation.

multiplicative identity
  ایدانی ِ بستایشی   
idâni-ye bastâyeši

Fr.: identité multiplicative   

The number which when used as the multiplier of another number leaves the second unchanged; one.

multiplicative; → identity.


Fr.: multiplicité   

1) The state of being multiple, made of several components.
2) In atomic and nuclear physics, the number of → levels into which the energy of an atom, molecule, or nucleus splits as a result of → Russell-Saunders coupling between → orbital angular momentum and → spin angular momentum. It is given by 2S+1, where S is the total electron → spin quantum number. The multiplicity of an energy level is indicated by a left superscript to the value of L, where L is the resultant electron orbital angular momentum of the individual electron orbital angular momenta.
3) In → statistical mechanics, the number of → microstates corresponding to a given → macrostate.

multiple; → -ity.

n-type conductivity
  هازندگی ِ گونه‌ی ِ n   
hâzandegi-ye gune-ye n

Fr.: conductivité de type n   

The conductivity in a semiconductor caused by a flow of electrons, whereas p-type conductivity is caused by a flow of holes.

n standing for → negative; → type; → conductivity.

naked singularity
  تکینی ِ برهنه   
takini-ye berehné (#)

Fr.: singularité nue   

A singularity that is not surrounded by an event horizon. It will therefore be visible and communicable to the outside world.

naked; → singularity.

nasal cavity
  کاواک ِ بینی، ~ دماغ   
kâvâk-e bini, ~ damâq

Fr.: cavité nasale   

The interior of the → nose. It is the structure which extends from the external opening, the → nostrils, to the → pharynx, where it joins the respiratory system.

nasal; → cavity.


Fr.: nationalité   

1) National status; specifically: a legal relationship involving allegiance on the part of an individual and usually protection on the part of the state b : membership in a particular nation.
2) Membership in a particular nation (

national; → -ity.


Fr.: nébulosité   

1) A nebulous form, shape, or mass.
2) The state or condition of being nebulous.
3) A fuzzy celestial object, constituted of gas and dust, generally part of a larger → nebula.

nebulous; → -ity.

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