An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



<< < abs col dep hyp mas per pos Ros sup tru > >>

Number of Results: 188 Search : sit
absolute luminosity
  تابندگی ِ ا َوَست   
tâbandegi-ye avast

Fr.: luminosité absolue   

A star's → intrinsic brightness, i.e. the total amount of energy radiated by the star per second. → Luminosity is often expressed in units of watts or erg/sec. The Sun's absolute luminosity is 3.86 × 1033 erg/sec.

absolute; → luminosity.

absolute viscosity
  وشکسانی ِ اوست   
vošksâni-ye avast

Fr.: viscosité absolue   

Same as → viscosity and → dynamic viscosity.

absolute; → viscosity.

Airy transit circle
  پرهون ِ نیمروزانی ِ ایری   
parhun-e nimruzâni-ye Airy

Fr.: circle méridien d'Airy   

A → transit circle that defines the position of the → Greenwich Meridian since the first observation was taken with it in 1851. Airy's transit circle lies at longitude 0°, by definition, and latitude 51° 28' 38'' N.

Named after Sir George Biddell Airy (1801-1892), Astronomer Royal, at the Royal Observatory in Greenwich from 1835 to 1881. Airy transformed the observatory, installing some of the most advanced astronomical apparatus of his day and expanded both staff numbers and their workload; → transit; → circle.

anomalous luminosity effect
  اسکر ِ تابندگی ِ ناسان   
oskar-e tâbandegi-ye nâsân

Fr.: effet luminosité anormale   

Discrepant luminosity classes derived for the same → Am star when different criteria are used. Lore specifically, a luminosity criterion may indicate a → giant star, wheras another criterion indicates a → supergiant.

anomalous; → luminosity; → effect.

apparent position
  نهش ِ پدیدار، جا‌ی ~   
naheš-e padidâr, jâ-ye ~

Fr.: position apparente   

1) The position on the celestial sphere at which a heavenly body would be seen from the Earth at a particular time.
2) A position given by the coordinates calculated for a star, if it were seen from the Earth's centre, relative to the → real equator and the → real equinox, at a certain date. It includes the displacements from one heliocentric direction, given in a stellar catalogue, due to → precession, → nutation, → aberration, → proper motions, → annual parallax, and light gravitational deviation (M.S.: SDE).

apparent; → position.

astronomical site
  سیت ِ اخترشناسیک، ~ اخترشناختی   
sit-e axtaršenâsik, ~ axtaršenâxti

Fr.: site astronomique   

A certain place whose characteristics, as to location, altitude, atmospheric conditions, etc., make it appropriate for astronomical observations.

astronomical; → site.

atomic proposition
  گزاره‌ی ِ اتمی   
gozâre-ye atomi

Fr.: proposition atomique   

In → propositional logic, a → sentence without any → connectives. See also → molecular proposition.

atomic; → proposition.

atomic transition
  گذرش ِ اتمی   
gozareš-e atomi

Fr.: transition atomique   

A change in the → energy level or state of an atom in which a → quantum of energy is either gained or lost. See also → forbidden transition; → permitted transition; → semiforbidden transition.

atomic; → transition.


Fr.: biodiversité   

The → variety of → plant and → animal → species in a particular → environment.

bio-; → diversity.

bolometric luminosity
  تابندگی ِ تاوسنجی، ~ تاوسنجیک   
tâbandegi-ye tâvsanji, ~ tâvsanjik

Fr.: luminosité bolométrique   

The total rate of energy output of an object integrated over all wavelengths.

bolometric; → luminosity.

bound-bound transition
  گذرش ِ بندیده-بندیده   
gozareš-e bandidé-bandidé

Fr.: transition liée-liée   

A transition between two energy levels of an electron bound to a nucleus. The electron remains tied to the nucleus before and after the transition. → bound-free transition; → free-free emission.

Bound, p.p. of → bind; → transition.

bound-free transition
  گذرش ِ بندیده-آزاد   
gozareš-e bandidé-âzâd

Fr.: transition liée-libre   

A transition in which a bound electron is liberated. → free-bound emission; → free-free emission.

Bound, p.p. of → bind; → free.

break luminosity
  تابندگی ِ بره   
tâbandegi-ye boré

Fr.: luminosité de coupure   

A characteristic luminosity around which the → luminosity function of a sample of galaxies changes to a steeper slope or exponentially declines.

break; → luminosity.

cascade transition
  گذرش ِ پی‌شاری   
gozareš-e peyšâri

Fr.: transition en cascade   

A photon generation mechanism in an atom in which a transition initiates a series of secondary transitions from lower electronic levels.

cascade; → transition.

catalog position
  نهش ِ کاتالوگی   
neheš-e kâtâlogi

Fr.: position catalogue   

Same as catalog place and → mean catalog place.

catalog; → position.

categorical proposition
  گزاره‌ی ِ کتاگریک   
gozâre-ye katâgorik

Fr.: proposition catégorique   

In a → syllogism, a → proposition or statement that deals with inclusion or exclusion of members of → subject classes in → predicate classes. Categorical propositions are of four basic forms, see → Aristotelian form.

categorical; → proposition.

charge density
  چگالی ِ بار   
cagâli-ye bâr

Fr.: densité de charge   

The → electric charge per unit volume in space, or per unit area on a surface, or per unit length of a line. They are respectively called volume- (ρ), surface- (σ), or line (λ) charge density.

charge; → density.

chemical composition
  همنهش ِ شیمیک   
hamneheš-e šimik

Fr.: composition chimique   

The identities, and relative abundances of the → chemical elements or → compounds that make up a substance.

chemical; → composition.

coefficient of viscosity
  همگر ِ وشکسانی   
hamgar-e vošksâni

Fr.: coefficient de viscosité   

A quantity that indicates a property of fluids and is defined by the ratio of shearing → stress to the rate of change of shearing → strain. It is also simply called viscosity. The coefficient of viscosity is expressed by: μ = (F/A) / (dv/dy), where F is the force required to maintain a steady velocity difference dv between any two parallel layers of the fluid, A is the area of the layers, and dv/dy is the → velocity gradient between two points separated by a small distance measured at right angles to the direction of flow. The unit of viscosity is that of force times distance divided by area times velocity. Thus, in the cgs system, the unit is 1, which reduces to 1 dyne.s/cm2. This unit is called 1 → poise.

viscosity; → coefficient.

color-luminosity diagram
  نمودار ِ رنگ-تابندگی   
nemudâr-e rang-tâbandegi

Fr.: diagramme couleur-luminosité   

A form of → Hertzsprung-Russell diagram in which the luminosity is the vertical axis and the → color index the horizontal axis.

color; → luminosity, → diagram.

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