# An Etymological Dictionary of Astronomy and AstrophysicsEnglish-French-Persian

## فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

### M. Heydari-Malayeri    -    Paris Observatory

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 mass flow   تچان ِ جرم   tacân-e jermFr.: écoulement de masse   The mass of a fluid that passes a specified unit area in a unit amount of time.→ mass; → flow. mass formula   دیسول ِ جرم   disul-e jermFr.: formule de masse   An → equation expressing the → atomic mass of a → nuclide as a function of its → mass number and the → atomic mass unit.→ mass; → formula. mass fraction   برخه‌ی ِ جرم   barxe-ye jermFr.: fraction de masse   The fractional amount (by mass) of a given → chemical element or → nuclide in a given → chemical composition. In chemical composition studies of astrophysical objects the mass fractions of → hydrogen, → helium, and all the remaining chemical elements are usually denoted by the parameter X, Y, and Z, respectively. Their sum is defined as X + Y + Z = 1. The parameter Z is usually referred to as → heavy elements or → metals.→ mass; → fraction. mass function   کریای ِ جرم   karyâ-ye jermFr.: fonction de masse   1) The number of a class of objects as a function of their mass. → initial mass function (IMF); → present-day mass function (PDMF). 2) A numerical relation between the masses of the two components of a → spectroscopic binary that provides information on the relative masses of the two stars when the spectral lines of only one component can be seen. If Mp is the mass of primary (whose spectrum is known), Ms is the mass of secondary, and i the → angle of inclination of the orbit, the mass function is given by: (Ms3. sin3i) / (Mp + Ms)2.→ mass; → function. mass loss   دسترفت ِ جرم   dastraft-e jermFr.: perte de masse   The outpouring of particles and gas from a star, occurring at varying rates and by a variety of processes throughout a star's lifetime. → Bipolar flows are believed to be due to mass loss by forming → protostars, while → massive stars lose their mass through powerful → stellar winds.→ mass; → loss. mass loss rate   نرخ ِ دسترفت ِ جرم   nerx-e dastraft-e jermFr.: taux de perte de masse   The rate with which the → mass loss process takes place, usually expressed in → solar mass per year. → radiation-driven mass loss. The mass loss rate and the → terminal velocity are anti-correlated, since the → wind momentum is constant, → bi-stability jump.→ mass loss; → rate. mass number   عدد ِ جرمی   adad-e jermi (#)Fr.: nombre de masse   The total number of → protons and → neutrons in the → atomic nucleus (symbol A). The mass number is written either after the → chemical element name or as a superscript to the left of an element's symbol. For example, the most common isotope of oxygen is oxygen-16, or 16O, which has 8 protons and 8 neutrons.→ mass; → number. mass outflow   استچان ِ جرم   ostacân-e jermFr.: écoulement de masse   The flowing out of mass through various processes from an object, for example in a star forming region or in a close binary.→ mass; → outflow. mass segregation   سوایش ِ جرم   savâyeš-e jermFr.: ségrégation de masse   A consequence of the → dynamical relaxation process in a gravitationally → bound system, such as a → star cluster or a → globular cluster, where massive and low-mass members occupy different volumes. Massive members sink toward the center, while less massive members tend to move farther away from the center.→ mass; → segregation. mass shift   کیب ِ جرمی   kib-e jermiFr.:   The portion of the isotope shift which results from the difference between the nuclear masses of different isotopes.→ mass; → shift. mass spectrometry   بیناب‌سنجی ِ جرم   binânsanji-ye jermFr.: spectrométrie de masse   An analytical technique for identification of chemical structures, determination of mixtures, and quantitative elemental analysis, in which ions are separated according to the mass/charge ratio and detected by a suitable detector.→ mass; → spectrometry. mass spectrum   بیناب ِ جرم   binâb-e jerm (#)Fr.: spectre de masse   A spectrum of charged particles, arranged in order of mass or mass-to-charge ratios. → mass spectrometry.→ mass; → spectrum. mass transfer   تراوژ ِ جرم   tarâvaž-e jermFr.: transfert de masse   The process in which the evolved member of a close binary system passes gaseous material to its companion star.→ mass; → transfer. mass transport   ترابرد ِ جرم   tarâbord-e jerm (#)Fr.: transport de masse   In fluid mechanics, the motion of a given amount of material carried by a fluid from one point to another.→ mass; → transfer. mass-energy equivalence   هموگ‌ارزی ِ جرم-کاروژ   hamug-arzi-ye jerm-kâružFr.: équivalence masse-énergie   The principle of interconversion of mass and energy, described by the → mass-energy relation.→ mass; → energy; → equivalence. mass-energy relation   باز‌آنش ِ جرم-کاروژ   bâzâneš-e jerm-kâružFr.: relation masse-énergie   The famous equation proposed by Einstein as a consequence of his special theory of relativity describing the equivalence of mass and energy: E = mc2, where E is energy, m is the equivalent amount of mass, and c is the velocity of light.→ mass; → energy; → relation. mass-luminosity ratio   وابر ِ جرم-تابندگی   vâbar-e jerm-tâbandegiFr.: rapport masse-luminosité   The ratio of the mass of a system, expressed in solar masses, to its visual luminosity, expressed in solar luminosities. The Milky Way Galaxy has a mass-luminosity ratio in its inner regions of about 10, whereas a rich cluster of galaxies such as the Coma Cluster has a mass-luminosity ratio of about 200, indicating the presence of a considerable amount of dark matter.→ mass; → luminosity; → ratio. mass-luminosity relation   باز‌آنش ِ جرم-تابندگی   bâzâneš-e jerm-tâbandegiFr.: relation masse-luminosité   A relationship between luminosity and mass for stars that are on the main sequence, specifying how bright a star of a given mass will be. Averaged over the whole main sequence, it has been found that L = M3.5, where both L and M are in solar units. This means, for example, that if the mass is doubled, the luminosity increases more than 10-fold.→ mass; → luminosity; → relation. mass-metallicity relation (MZR)   بازانش ِ جرم-فلزیگی   bâzâneš-e jerm-felezigiFr.: relation masse-métallicité   A correlation between the → stellar mass (or → luminosity) and the → gas metallicity of → star-forming galaxies (Lequeux et al. 1979) according to which massive galaxies have higher gas metallicities. Several large galaxy surveys, such as the → Sloan Digital Sky Survey (SDSS), have confirmed that galaxies at all → redshifts with higher stellar masses retain more metals than galaxies with lower stellar masses. Besides the dependence on stellar mass, other studies have found further dependences of gas metallicity on other physical properties at a given mass, such as → specific star formation rate, → star formation rate, and stellar age. These higher dimensional relations could provide additional constraints to the processes that regulate the metal enrichment in galaxies. In addition to gas metallicity, also the → stellar metallicity of galaxies is found to correlate with the stellar mass, suggesting the mass-metallicity relation already existed at early epochs of galaxy evolution (Lian et al., 2017, MNRAS 474, 1143, and references therein).→ mass; → metallicity; → relation. mass-size relation   بازانش ِ جرم-اندازه   bâzâneš-e jerm-andâzeFr.: relation masse-taille   The relation between the → stellar mass and the physical size of a galaxy. Studies show that the sizes increase with stellar mass, but that the relation weakens with increasing → redshift. Separating galaxies by their → star formation rate, model simulations show that → passive galaxies are typically smaller than → active galaxies at a fixed stellar mass. These trends are consistent with those found in observations; the level of agreement between the predicted and observed size-mass relations is of the order of 0.1 dex for redshifts < 1 and 0.2-0.3 dex from redshift 1 to 2. Known also as the → luminosity-size relation (Furlong et al., 2016, MNRAS 465, 722, and references therein).→ mass; → size; → relation.