An Etymological Dictionary of Astronomy and Astrophysics
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فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 100 Search : mass
airmass
  هواتود، توده‌ی ِ هوا   
havâtud, tude-ye havâ (#)

Fr.: masse d'air   

A measure of the path length traversed by starlight through Earth's atmosphere before it reaches the detector; it is taken relative to the length at the zenith.

air; → mass.

amass
  انباشتن   
anbâštan (#)

Fr.: amasser   

1) To collect into a mass or pile; → accumulate.
2) To gather for oneself; collect as one's own (Dictionary.com).

M.E., from O.Fr. amasser, from à "to," → ad-, + masser "to gather in mass," → mass.

Anbâštan, anbârdan "to fill, to replete," from Mid.Pers. hambāridan "to fill;" from Proto-Iranian *ham-par-, from prefix ham-, → com-, + par- "to fill;" cf. Av. par- "to fill," parav-, pauru-, pouru- "full, much, many;" O.Pers. paru- "much, many;" Mid.Pers. purr "full;" Mod.Pers. por "full, much, very;" PIE base *pelu- "full," from *pel- "to be full;" cf. Skt. puru- "much, abundant;" Gk. polus "many," plethos "great number, multitude;" O.E. full.

atomic mass number (A-number)
  عدد ِ جرم ِ اتمی   
adad-e jerm-e atomi (#)

Fr.: nombre de masse atomique   

The total number of protons and neutrons in the nucleus of an atom. For example, Oxygen-16 has a mass number of sixteen, because it has eight protons and eight neutrons.

atomic; → mass; → number.

atomic mass unit (amu)
  یکای ِ جرم ِ اتمی   
yekâ-ye jerm-e atomi (#)

Fr.: unité de masse atomique   

A unit of mass used for atoms and molecules, equal to 1/12 of the mass of an atom of carbon-12 (including orbital electrons). It is equal to 1.660 33 × 10-24 g.

atomic; → mass; → unit.

binary supermassive black hole
  سیه‌چال ِ ابر-پرجرم ِ درین   
siyah-câl-e abar-porjerm-e dorin

Fr.: trou noir supermassif double   

A → dual supermassive black hole whose components are separated by a few parsecs.

binary; → supermassive; → black; → hole.

Bonnor-Ebert mass
  جرم ِ بونور-ابرت   
jerm-e Bonnor-Ebert

Fr.: masse de Bonnor-Ebert   

The largest gravitationally stable mass of the → Bonnor-Ebert sphere.

After W.B. Bonnor (1956) and R. Ebert (1955); → mass.

center of mass
  گرانیگاه   
gerânigâh (#)

Fr.: centre de masse   

Same as → center of gravity, → center of inertia, → centroid, and → barycenter.

center; → mass.

characteristic mass
  جرم ِ سرشتاری   
jerm-e sereštâri

Fr.: masse caractéristique   

A typical or most likely mass for the formation of an astronomical object. In current star formation models, it is of order of a few tenths of a → solar mass.

characteristic; → mass.

cluster mass function (CMF)
  کریای ِ جرم ِ خوشه   
karyâ-ye jerm-e xušé

Fr.: fonction de masse d'amas   

An empirical power-law relation representing the number of clusters as a function of their mass. It is defined as: N(M)dM ∝ MdM, where the exponent α has an estimated value of about 2 and dM is the mass interval. It is believed that this is a universal law applying to a variety of objects including globular clusters, massive young clusters, and H II regions.

cluster; → mass; → function.

compact massive galaxy (CMG)
  کهکشان ِ پرجرم ِ همپک   
kahkešân-e porjerm-e hampak

Fr.: galaxie massive compacte   

A galaxy with a stellar mass of M ≥ 1011Msun and an → effective radius of Re ≤ 1.5 kpc. Many studies have shown that massive galaxies with low → star formation rates were remarkably compact at a → redshift of z≥ 2. At fixed stellar mass of Mstars ≅ 1011Msun, quiescent galaxies are a factor of ~ 4 smaller at z = 2 than at z = 0. As the stellar mass of the galaxies also evolves, the inferred size growth of individual galaxies is even larger. It is unlikely that all massive galaxies in the present-day Universe had a compact progenitor. However, the vast majority of CMGs that are observed at z = 2 ended up in the center of a much larger galaxy today. Their size growth after z = 2 is probably dominated by minor → mergers. Such mergers are expected because other mechanisms cannot easily produce the observed scaling between size growth and mass growth (P. G. van Dokkum1 et al., 2015, ApJ 813, 23).

compact; → massive; → galaxy.

conservation of mass
  پایش ِ جرم   
pâyeš-e jerm

Fr.: conservation de masse   

A → principle of → classical physics whereby → matter can be neither created nor destroyed. Matter can, however, be → converted into → energy, as predicated by the theory of → special relativity. Also called → conservation of matter.

conservation; → mass.

conservation of mass and energy
  پایش ِ جرم و کاروژ   
pâyeš-e jerm o kâruž

Fr.: conservation de masse et d'énergie   

A principle, resulting from Einstein's theory of → special relativity whereby in any → closed system the sum of mass and energy remains → constant.

conservation; → mass; → energy.

core mass function (CMF)
  کریای ِ جرم ِ مغزه   
karyâ-ye jerm-e maqzé

Fr.: fonction de masse des cœurs   

The mass distribution of → pre-stellar cores in → star-forming regions. The CMF is usually represented by dN/dM = Mα, where dM is the mass interval, dN the number of cores in that interval, and α takes different values in different mass ranges. In the case of → low-mass stars, it is found that the CMF resembles the → Salpeter function, although deriving the masses and radii of pre-stellar cores is not straightforward. The observational similarity between the CMF and the → initial mass function (IMF) was first put forth by Motte et al. (1988, A&A, 336, 150), and since then many other samples of dense cores have been presented in this context. For example, Nutter & Ward-Thompson (2007, MNRAS 374, 1413), using SCUBA archive data of the Orion star-forming regions, showed that the CMF can be fitted to a three-part → power law consistent with the form of the stellar IMF. Recent results, obtained using observations by the → Herschel Satellite, confirm the similarity between the CMF and IMF with better statistics (Könyves et al. 2010, A&A, 518, L106; André et al. 2010, A&A, 518, L102). Moreover, these works show that the CMF has a → lognormal distribution (i.e. dN/dlog M follows a → Gaussian form against log M), as is the case for the IMF at low masses (below about 1 solar mass).

core; → mass; → function.

coronal mass ejection (CME)
  اشانش ِ جرم از هورتاج   
ešâneš-e jerm az hurtâj

Fr.: éjection de masse coronale   

A huge eruption of material from regions of the solar corona in which the magnetic field is closed, but which suffer an extremely energetic disruption. Over the course of several hours up to 10,000 billion kg of this material is ejected into → interplanetary space with a a speed of as high as 3000 km/s. CMEs are most spectacularly observed by a white light coronagraph located outside Earth's atmosphere. Such observations from Skylab in the early 1970's were the first to reveal this phenomenon. CME's disrupt the flow of the → solar wind and can produce intense electromagnetic disturbances that can severely damage satellites and disrupt power grids on Earth. When these ejections reach the Earth, they give rise to → geomagnetic storms. The frequency varies with the → solar cycle; during solar minimum they come at a rate of about one per week, and during maximum there is an average of about two or three per day. See also → interplanetary coronal mass ejections (ICME).

coronal; → mass; → ejection.

critical Bonnor-Ebert mass
  جرم ِ پرژنی ِ بونور-ابرت   
jerm-e paržani-ye Bonnor-Ebert

Fr.: masse critique de Bonnor-Ebert   

The upper value of mass that a → Bonnor-Ebert sphere must have in order that → hydrodynamic equilibrium be maintained. This → critical mass is given by: Mcrit = 1.18 (a4/G3/2)Pext-1/2, where a = (kT/m)1/2 is the isothermal → sound speed inside the sphere, G is the → gravitational constant, and Pext the pressure of the external medium (see, e.g., F. H. Shu, 1977, ApJ 214, 488).

critical; → Bonnor-Ebert mass.

critical mass
  جرم ِ پرژنی   
jerm-e paržani

Fr.: masse critique   

Of a fissile material (235U or 239Pu), the minimum mass needed for a sustained nuclear chain reaction, as in an atomic bomb.

critical; → mass.

dense core mass function
  کریای ِ جرم ِ مغزه‌ی ِ چگال   
karyâ-ye jerm-e maqze-ye cagâl

Fr.: fonction de masse des cœurs denses   

core mass function.

dense; → core; → mass; → function.

dual supermassive black hole
  سیه‌چال ِ ابر-پرجرم ِ دوگانه   
siyah-câl-e abar-porjerm-e dogâné

Fr.: trou noir supermassif double   

The outcome of a → merger process between two galaxies, each with its own central → supermassive black hole (SMBH), resulting in a remnant galaxy hosting two SMBHs. Simulations of → galaxy mergers show there should be lots of dual → active galactic nuclei (AGN) visible at less than 10 kpc separations. As of 2015 more than 100 known dual supermassive black holes have been found. See also → binary supermassive black hole.

dual; → supermassive; → black; → hole.

dynamical mass
  جرم ِ توانیک   
jerm-e tavânik

Fr.: masse dynamique   

The mass of an object derived indirectly from theoretical formulae based on the laws governing the behavior of a → dynamical system.

dynamical; → mass.

Earth mass
  جرم ِ زمین   
jerm-e zamin (#)

Fr.: masse de la Terre   

The mass of our planet Earth, which is 5.9736 × 1024 kg, 317.83 times smaller than the → Jupiter mass. The Earth mass is in particular used to describe the mass of → super-Earth  → extrasolar planets.

Earth; → mass.

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