An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory

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Number of Results: 128 Search : form
star formation region
  ناحیه‌ی ِ دیسش ِ ستاره   
nâhiye-ye diseš-e setâré

Fr.: région de formation d'étoiles   

A region in the → interstellar medium where processes of → star formation are going on or have occurred in the past.

star; → formation; → region.

star formation time scale
  مرپل ِ زمانی ِ دیسش ِ ستاره   
marpel-e zamâni-ye diseš-e setâre

Fr.: échelle de temps de formation d'étoiles   

The time necessary for a star to form. It depends inversely on the stellar mass.

star formation; → time scale.

star-forming galaxy
  کهکشان ِ دیسنده‌ی ِ ستاره   
kahkešân-e disnade-ye setâré

Fr.: galaxie de formation d'étoiles   

A galaxy that is located on the → galaxy main sequence in the plane relating → star formation rates to total stellar masses.

star; → formation; → galaxy.

star-forming region
  ناحیه‌ی ِ دیسش ِ ستاره   
nâhiye-ye diseš-e setâré

Fr.: région de formation d'étoiles   

A region in which → star formation is going on.

star; → formation; → region.

stimulated star formation
  دیسش ِ گوالیده‌ی ِ ستاره   
diseš-e gavâlide-ye setâré

Fr.: formation stimulée d'étoiles   

A process in which a star is not formed spontaneously but is provoked by the action of external forces, such as pressure and shock on a molecular cloud by close-by → massive stars, → supernova explosions, etc. See also → sequential star formation.

Stimulated, p.p. of → stimulate; → star formation.

stochastic self-propagating star formation
  دیسش ِ ستارگان با خود-توچش ِ کاتورگین   
diseš-e setâregân bâ xod-tuceš-e kâturgin

Fr.: formation d'étoiles par auto-propagation stochastique   

A mechanism that could be responsible for global → spiral structure in galaxies either by itself or in conjunction with spiral → density waves. In this mechanism, star formation is caused by → supernova-induced → shocks which compress the → interstellar medium. The → massive stars thus formed may, when they explode, induce further → star formation. If conditions are right, the process becomes self-propagating, resulting in agglomerations of young stars and hot gas which are stretched into spiral shaped features by → differential rotation. Merging of small agglomerations into larger ones may then produce large-scale spiral structure over the entire galaxy. The SSPSF model, first suggested by Mueller & Arnett (1976) was developed by Gerola & Seiden (1978). While the → density wave theory postulates that spiral structure is due to a global property of the galaxy, the SSPSF model examines the alternative viewpoint, namely that spiral structure may be induced by more local processes. The two mechanisms are not necessarily mutually exclusive, but they involve very different approaches to the modeling of galaxy evolution. The SSPSF gives a better fit than the density wave theory to the patchy spiral arms found in many spiral galaxies. However, it cannot explain → galactic bars.

stochastic; → self; → propagate; → star; → formation.

structure formation
  دیسش ِ ساختار   
diseš-e sâxtâr

Fr.: formation des structures   

The study of the processes that gave rise to the apparition of matter concentrations, such as → superclusters of galaxies, → galaxy clusters, and galaxies, in a homogeneous → expanding Universe. Cosmic structures are believed to result from → density fluctuations that existed in the → early Universe before radiation and matter decoupled (→ decoupling era or → recombination era). Initial → quantum fluctuations in the → inflaton field were expanded by → inflation. Inflation amplified them up to scales that correspond to those of galaxy clusters and beyond. Generally, a model of structure formation includes three main ingredients: 1) background cosmology, 2) model for fluctuation generation, and 3) types of → dark matter.
See also:
bottom-up structure formation, → hierarchical structure formation, → Silk damping, → top-down structure formation.

structure; → formation.

terraform
  زمین‌دیسیدن   
ziman-disidan

Fr.: terraformer   

To alter the environment of a planet or moon in a → terraforming process in order to make it habitable for life forms.

Probably taken from noun terraform, from L. terra "earth," → terrestrial; → form.

From zamin, → earth, + disidan "to → form."

terraforming
  زمین‌دیسش   
zamin-diseš

Fr.: terraformation   

The hypothetical process of altering the environment (atmosphere, temperature, surface topography, or ecology) of another planet or moon to improve the chances of survival of an indigenous biology or to allow habitation by terrestrial life forms. See also → ecopoiesis.

Verbal noun of → terraform. The term first appeared in a science fiction novel, Seetee Shock (1949) by Jack Williamson, an American science fiction writer; but the actual concept pre-dates this work.

top-down structure formation
  دیسش ِ ساختار از بالا به پایین   
diseš-e sâxtâr az bâlâ bé pâyin

Fr.: formation des structures du haut vers le bas   

A cosmological model of → structure formation in which larger structures, such as galaxy → superclusters or perhaps even the vast → filaments and → voids, form earlier and then they fragment into smaller structures such as individual galaxies. Opposite of → bottom-up structure formation.

top; → down; → structure; → formation.

transform
  ۱) ترادیس؛ ۲) ترادیسیدن   
1) tarâdis (#); 2) tarâdisidan (#)

Fr.: 1) transformée, transformation; 2) transformer   

1) Math.: A mathematical quantity obtained from a given quantity by an algebraic, geometric, or functional transformation.
The transformation itself.
2) To change in form, appearance, or structure; to change in condition, nature, or character; convert.
Physics: To change into another form of energy.
To increase or decrease (the voltage and current characteristics of an alternating-current circuit), as by means of a transformer.
Math.: To change the form of (a figure, expression, etc.) without in general changing the value.

trans- + → form.

transformation
  ترادیسش، ترادیس   
tarâdiseš (#), tarâdis (#)

Fr.: transformation   

1) The act or process of transforming. The state of being transformed.
2) The relationship between description of a physical phenomenon in one → reference frame to another. → Galilean transformation; → Lorentz transformation.
3) Math.: The act, process, or result of transforming or mapping.

Verbal noun of → transform.

transformer
  ترادیسگر، ترادیسنده   
tarâdisgar (#), tarâdisandé (#)

Fr.: transformateur   

A device that converts low voltages to higher voltages, or vice versa. A transformer consists of a primary coil and a secondary coil, both traversed by the same magnetic flux.

transform + → -or.

triggered star formation
  دیسش ِ ماشه‌ای ِ ستاره   
diseš-e mâše-yi-ye setâré

Fr.: formation d'étoiles déclanchée   

The formation of second-generation stars in a → molecular cloud, as set off by the action of → massive stars. → sequential star formation; → radiation-driven implosion.

trigger; → star formation.

uniform
  یکدیس، یکنواخت   
yekdis, yeknavâxt

Fr.: uniforme   

Without variations; identical, always the same in quality, degree, character, or manner.

uni- + → form.

Yekdis, from yek, → uni-, + dis, → form; yeknavâxt, literally "with one rhythm," from yek, → one, + navâxt "rhythm," from navâxtan, navâzidan "to play an instrument; to gratify," navâ "music, song, melody" (Mid.Pers. nw'c "to treat kindly, honour," niwag "music, melody;" Proto-Iranian *ni-uac-, from ni- "down; into," → ni- (PIE), + *uac- "to speak, treat kindly").

uniform circular motion
  جنبش ِ دایره‌ای ِ یکدیس، ~ ~ یکنواخت   
jonbeš-e dâyereyi-ye yekdis, ~ ~ yeknavâxt

Fr.: mouvement circulaire uniforme   

The motion of an object around a fixed point at a constant angular speed, and at constant radius.

uniform; → circular; → motion.

uniform field
  میدان ِ یکدیس، ~ ِ یکنواخت   
meydân-e yekdis, ~ yeknavâxt

Fr.: champ uniforme   

A field that at a given instant has the same value at all points within a specified region of interest.

uniform; field.

uniform magnetic field
  میدان ِ مغناتیسی ِ یکدیس   
meydân-e meqnâtisi-ye yekdis

Fr.: champ magnétique uniforme   

A → magnetic field whose direction does not change and whose strength is constant at every point.

uniform; → magnetic; → field.

uniform motion
  جنبش ِ یکدیس، ~ ِ یکنواخت   
jonbeš-e yekdis, ~ yeknavâxt

Fr.: mouvement uniforme   

Motion at a constant → velocity. The state of rest is a special case of uniform motion. → accelerated motion; → inertial motion.

uniform; motion.

uniformitarian
  یکدیسوار   
yekdisvâr

Fr.: uniformitaire   

1) Of, characterized by, or conforming to → uniformity.
2) Of or relating to → uniformitarianism.

uniformity + -arian.

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