An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 80 Search : forma
affine transformation
  ترادیس ِ کروَن   
tarâdis-e karvan

Fr.: transformation affine   

Any → transformation preserving → collinearity.

affine; → transformation.

biased galaxy formation
  دیسش ِ ورکدار ِ کهکشانها   
diseš-e varakdâr-e kahkašânhâ

Fr.: formation biaisée de galaxies   

The theory that bright galaxies form preferentially from anomalously overdense perturbations in the → early Universe.

biased; → galaxy; → formation.

bimodal star formation
  دیسش ِ دومد ِ ستارگان   
diseš-e domod-e setâregân

Fr.: formation bimodale d'étoile   

A concept of → star formation in which → high-mass stars and → low-mass stars form in different physical conditions involving different → molecular clouds. Following the pioneering suggestion of Herbig (1962), successive investigations have generally supported the idea that star formation proceeds bimodally with respect to stellar mass. The star formation rate appears to differ both spatially and temporally for low mass and → massive stars. This is of considerable importance for galactic evolution, since the low-mass stars lock up mass and are long-lived, low luminosity survivors to the present epoch, whereas massive stars are short-lived, recycle and enrich interstellar gas, and leave dark remnants while producing a high luminosity per unit of mass (Silk, J., 1988, in Galactic and Extragalactic Star Formation, p. 503, eds. R. E. Pudritz and M. Fich).

bimodal; → star; → formation.


Fr.: bioinformatique   

The retrieval and analysis of biochemical and biological data using mathematics and computer science, as in the study of genomes (

bio-; → informatics.

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

Fr.: formation des structures du bas vers le haut   

A → structure formation scenario in which small galaxies form first, and larger structures are then formed in due course. Contrary to → top-down structure formation.

bottom; → up; → structure; → formation; → galaxy.

burst of star formation
belk-e diseš-e setâregân

Fr.: flambée de formation d'étoiles   

An intense → star formation activity in a region of → interstellar medium or, more globally, in a → galaxy. It is characterized by a → star formation rate which is much higher than the corresponding average. Same as → starburst.

burst; → star; → formation.

cluster formation efficiency (CFE)
  کارایی ِ دیسش ِ خوشه   
kârâyiè-ye diseš-e xuše

Fr.: efficacité de formation d'amas   

The fraction of → star formation which happens in → bound clusters. It is defined as the ratio between the → cluster formation rate and → star formation rate (Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).

cluster; → formation; → efficiency.

cluster formation rate (CFR)
  نرخ ِ دیسش ِ خوشه   
nerx-e diseš-e xuše

Fr.: taux de formation d'amas   

A parameter used in star formation models representing the ratio of the total mass in → star clusters to the corresponding age range (Bastian, 2008, MNRAS 390, 759, arxiv/0807.4687).

cluster; → formation; → rate.

CO formation
  دیسش ِ CO   
diseš-e CO

Fr.: formation de CO   

The chemical reaction that gives rise to → carbon monoxide in the → interstellar medium. According to models, several processes may lead to CO formation. For example, HCO+ + e → CO + H. The molecule HCO+ is itself produced through several paths, for example: H3+ + C → CH2+ + H, CH2+ + H2 → CH3+ + H, CH3+ + O → HCO+ + H. Alternatively: C+ + H2O → HCO+ + H. Another possibility: C+ + OH → CO+ + H, CO+ + H2→ HCO+ + H.

carbon monoxide; → formation.

collective star formation
  دیسش ِ گرد‌آمدی ِ ستارگان   
diseš-e gerdâmdi-ye setâregân

Fr.: formation collective d'étolies   

Formation of stars, especially → massive stars, in group as opposed to individual formation.

collective; → star; → formation.

color transformation
  ترادیس ِ رنگ   
tarâdis-e rang

Fr.: transformation de couleur   

Empirical mathematical transformation applied to the observed magnitudes in order to convert them into a standard system, or into a different system.

color; → transformation.


Fr.: conforme   

1) That conforms, especially to the shape of something.
2) Math.: Of, pertaining to, or specifying a mapping of a surface upon another surface so that all angles between intersecting curves remain unchanged.

con- + → form + → -al.

conformal compactification
  همپکانش ِ همدیس   
hampakâneš-e hamdi

Fr.: compactification conforme   

A mapping of an infinite → space-time onto a finite one that may make the far away parts of the former accessible to study. The technique invented by Penrose defines an equivalence class of → metrics, gab being equivalent to ĝab = Ω2gab, where Ω is a positive scalar function of the space-time that modifies the distance scale making the asymptotics of the physical metric accessible to study.

conformal; → compactification.

conformal cyclic cosmology (CCC)
  کیهانشناسی ِ چرخه‌ای ِ همدیس   
keyhânšenâsi-ye carxe-yi-ye hamdis

Fr.: cosmologie cyclique conforme   

A cosmological model developped by Roger Penrose and colleagues according which the Universe undergoes repeated cycles of expansion. Each cycle, referred to an aeon, starts from its own "→ big bang" and finally comes to a stage of accelerated expansion which continues indefinitely. There is no stage of contraction (to a "→ big crunch") in this model. Instead, each aeon of the universe, in a sense "forgets" how big it is, both at its big bang and in its very remote future where it becomes physically identical with the big bang of the next aeon, despite there being an infinite scale change involved, on passing from one aeon to the next. This model considers a conformal structure rather than a metric structure. Conformal structure may be viewed as family of metrics that are equivalent to one another via a scale change, which may vary from place to place. Thus, in conformal space-time geometry, there is not a particular metric gab, but an equivalence class of metrics where the metrics ğab and gab are considered to be equivalent if there is a smooth positive scalar field Ω for which ğab = Ω gab (R. Penrose, 2012, The Basic Ideas of Conformal Cyclic Cosmology).

conformal; → cyclic; → cosmology.

conformal geometry
  هندسه‌ی ِ همدیس   
hendese-ye hamdis

Fr.: géométrie conforme   

The study of the set of angle-preserving transformations on a space.

conformal; → geometry.

conformal mapping
  همتایش ِ همدیس   
hamtâyeš-e hamdis

Fr.: application conforme   

A continuous mapping u = f(x) of a domain D in an n-dimensional Euclidean space (n≥ 2) into the n-dimensional Euclidean space is called conformal at a point x0D if it has the properties of constancy of dilation and preservation of angles at this point.

conformal; → mapping.

cosmic star formation peak
  چکاد ِ کیهانی ِ دیسش ِ ستارگان   
cakâd-e keyhâni-ye diseš-e setâregân

Fr.: pic de formation stellaire cosmique   

A crucial period in the history of the → Universe, when the bulk of stars in massive galaxies were likely formed. Observations of young stars in distant galaxies at different times in the past have indicated that the → star formation rate peaked at the → redshift of z ~ 2, some 10 billion years ago, before declining by a factor of around ten to its present value (P. Madau & Dickinson, 2014, arXiv:1403.0007).

cosmic; → star; → formation; → peak.


Fr.: déformable   

Capable of being → deformed. → deformable mirror

deform + → -able.

deformable mirror
  آینه‌ی ِ وادیسیدنی   
âyene-ye vâdisidani

Fr.: miroir déformable   

A very thin mirror whose shape can be changed by the force applied by many small pistons behind the mirror. Such a mirror is used in the → adaptive optics technique to correct the → wavefront affected by the → atmospheric turbulence. See also → tip-tilt mirror.

deformable; → mirror.

  وادیس، وادیسش، وادیسانش   
vâdis, vâdiseš, vâdisâneš

Fr.: déformation   

Altering in the size or shape of a body. See also → deformable.

Verbal noun of → deform.

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