An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1334
barfrub (#)

Fr.: chasse-neige   

A piece of equipment mounted on the front of a vehicle for clearing away snow from roads, railroad tracks, etc.

snow + plow, → Plough.

Barfrub, from barf, → snow, + rub, rubidan "to sweep," → scan.

snowplow phase
  فاز ِ برفروب   
fâz-e barfrub

Fr.: phase de chasse-neige   

The third phase in the evolution of a → supernova remnant (SNR) occurring after the → Sedov-Taylor phase when the mass of the swept-up material becomes much larger than the amount of the ejected material. The SNR is surrounded by a cool → shell of accumulated material that is being pushed from behind, similar to what occurs for a snowplow. During this phase, → radiative cooling becomes important and the total energy is no longer conserved. Also called the → radiative phase.

snowplow; → phase.

SNR shell
  پوسته‌ی ِ بازمانده‌ی ِ اَبَر-نوختر   
pustey-e bâzmânde-ye abar-now-axtar

Fr.: coquille de reste de supernova   

A ring-like structure of swept-up → gas and → dust around a → supernova remnant. See also: → free expansion phase, → Sedov-Taylor phase, → snowplow phase.

supernova remnant (SNR); → shell.

Sobolev approximation
  نزدینش ِ سوبولف   
nazdineš-e Sobolev

Fr.: approximation de Sobolev   

A method allowing for a simplified solution to the → radiative transfer equation at frequencies of spectral lines in media moving with a high velocity gradient. This method assumes that the macroscopic velocity gradients are more important than local random variations of thermal line width: dv/dr > vth/l, where dv/dr is the velocity gradient, vth is the thermal broadening of the line, and l the length scale. The Sobolev approximation is only valid if the conditions of the gas do not change over the → Sobolev length. Under the Sobolev approximation, each point in the medium is isolated from other points, and the → radiative transfer problem becomes a local one and therefore much easier to solve.

Named after the Russian astronomer Viktor Viktorovich Sobolev, Moving Envelopes of Stars [in Russian], Leningr. Gos. Univ., Leningrad (1947) [translated by S. Gaposchkin, Harvard Univ. Press, Cambridge, Mass. (1960)]; → approximation.

Sobolev length
  درازای ِ سوبولف   
derâzâ-ye Sobolev

Fr.: longueur de Sobolev   

In the → Sobolev approximation, the length over which the conditions of the gas do not change and the approximation is valid. It is expressed by: ls = vth/(dv/dr), where vth is the thermal line width and (dv/dr) the velocity gradient. In other words, the length over which the profile function of a line is shifted through a distance equal to its own width by the macroscopic velocity gradients that exist in the moving medium.

Sobolev approximation; → length.


Fr.: social   

Of or pertaining to human society.

society; → -al.


Fr.: socialisation   

A continuing process whereby an individual acquires a personal identity and learns the norms, values, behavior, and social skills appropriate to his or her social position (

socialize; → -tion.


Fr.: socialiser   

To make social; make fit for life in companionship with others (

social; → -ize.


Fr.: sociétal   

Of or pertaining to social groups, their activities, or to social relations.

From societ-, from → society, + → -al.

Hazâni, from hazân-, from hazâné, → society, + -i, → -al.


Fr.: société   

An organized group of persons associated together for scientific, cultural, or other purposes; e.g. a physical society. See also:
associate, → association, → dissociate, → dissociation, → social, → socialization, → socialize, → societal.

M.E., from O.Fr. societe, from L. societatem (nominative societas), from socius "companion," → associate.

Hazâné, from Av. hacenay- "getting together, association," from verb hac-, hax- "to associate, follow, accompany" (haxay-, hašy-, haš- "friend"), hacaiti "follows;" hacā "from, out of;" O.Pers. hacā "from" (Mid.Pers. hac "from;" Mod.Pers. az "from"); PIE base *sekw- "to follow;" cf. Skt. sac- "to be associated or united with," sácate "accompanies, follows," sácā "with;" Gk. hepesthai "to follow;" L. sequi "to follow."


Fr.: sociologie   

The science or study of the origin, development, organization, and functioning of human society; the science of the fundamental laws of social relations, institutions, etc. (

society; → -logy.

  سقراطی، سقراتی   

Fr.: socratique   

Of or pertaining to Socrates or his philosophy, followers, etc., → Socratic irony, → Socratic method.

Socrates (469?-399 B.C.), Athenian philosopher.

Socratic irony
  گواژه‌ی ِ سقراطی، ~ سقراتی   
govâže-ye Soqrâti

Fr.: ironie socratique   

A means by which the pretended ignorance of a skillful questioner leads the person answering to expose his own ignorance (Collins).

Socratic; → irony.

Socratic method
  روش ِ سقراطی، ~ سقراتی   
raveš-e Soqrâti

Fr.: méthode socratique   

The use of questions, as employed by Socrates, to develop a latent idea, as in the mind of a pupil, or to elicit admissions, as from an opponent, tending to establish a proposition (

Socratic; → method.

sodiom (#)

Fr.: sodium   

A metallic chemical element; symbol Na (L. natrium]. Atomic number 11; atomic weight 22.98977; melting point 97.81°C; boiling point 892.9°C; specific gravity 0.971 at 20°C. It was discovered in 1807 by the English chemist Humphry Davy from electrolysis of caustic soda (NaOH).

Sodium, from soda (NaOH).

sodium tail
  دم ِ سودیومی   
dom-e sodiomi

Fr.: queue de sodium   

1) A kind of → cometary tail appearing in some → comets, such as → Hale-Bopp. Sodium tails arise from the very strong → fluorescence of their sodium atom → D lines in the visible. They are rapidly accelerated to high velocities by the Sun, forming a very straight tail distinct from the → ion tail. The release mechanism of sodium from comets is still a matter of debate. Also called → neutral tail.
2) An enormous, comet-like tail of sodium gas stretching out behind the Moon, at least 800,000 km (many hundreds, and perhaps thousands, of lunar radii). The tail is due to the strong influence of the Sun's → radiation pressure on sodium atoms (→ D line) present in the → lunar exosphere. Near → new Moon phase, the extended lunar sodium tail can be observed as it sweeps over the Earth and is gravitationally focused into a visible sodium "spot" in the → anti-solar direction. It is too faint to be detected by the human eye.

sodium; → tail.

narm (#)

Fr.: mou   

General: Delicate in texture, grain, or fiber.
Not bright or glaring.
Physics: Of a beam of particles or electromagnetic radiation, having relatively low energy, as opposed to → hard. → soft X-rays

M.E. softe "yielding, gentle, mild;" O.E. softe "gentle, easy;" cf. O.S. safti, O.H.G. semfti, Ger. sanft, M.Du. sachte, Du. zacht.

Narm "soft; smooth; mild," from Mid.Pers. narm "soft; humble."

soft binary
  درین ِ نرم   
dorin-e narm

Fr.: binaire mou   

In → stellar dynamics studies of → three-body encounters, a → binary system whose → binding energy is smaller than the typical → kinetic energy of the relative motion of an incoming third body. See also → hard binary.

soft; → binary.

soft gamma repeater (SGR)
  بازگرشگر ِ گامای ِ نرم   
bâzgaršgar-e gâmmâ-ye narm

Fr.: répéteur gamma mou   

A member of a small class of objects which emit intense bursts of → gamma rays and → X-rays (> 100 keV) at irregular intervals. The bursts last for some 100 milli-seconds. It is conjectured that they are → magnetars. See also → starquake.

soft; → gamma rays; → repeater.

soft gamma-ray repeater (SGR)
  بازگرشگر ِ پرتوهای ِ گامای ِ نرم   
bâzgaršgar-e partowhâ-ye gâmmâ-ye narm

Fr.: répéteur des rayons gamma mous   

Same as → soft gamma repeater (SGR).

soft; → gamma ray; → repeater.

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