An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 41 Search : variable
action variable
  ورتنده‌ی ِ ژیرش   
vartande-ye žireš

Fr.: variable d'action   

The time integral associated with the evolution of a physical system in the phase space.

action; → variable.

Algol-type variables
  ورتندگان ِ الغولگونه   
vartandegân-e Alqulguné

Fr.: variables de type Algol   

The same as eclipsing binary stars, the prototype of which is Algol.

Algol; → variable.

Beta Cephei variable
  ورتنده‌ی ِ بتا-کفؤسی   
vartande-ye betâ Kefeusi

Fr.: variables bêta Céphée   

A variable star, of early B or late O types, undergoing radial pulsations with short periods (< 1 day). Beta Cephei stars are confined within a narrow band of the → H-R diagram above the upper → main sequence. They are believed to be near the end of core hydrogen-burning stars of approximately 10 to 20 solar masses. The famous bright stars → Spica and → Mirzam belong to this family.

Beta Cephei; → variable.

canonically conjugate variable
  ورتنده‌یِ هنجاروارانه همیوغ   
vartande-ye hanjârvârâné hamyuq

Fr.: variable canoniquement conjuguée   

A generalized coordinate and its → conjugate momentum.

Canonically, adverb from → canonical; → conjugate; → variable.

cataclysmic variable
  ورتنده‌ی ِ گتلوری   
vartande-ye gatluri

Fr.: variable cataclysmique   

A → variable star that shows a sudden and dramatic change in brightness, including → flare stars, → novae, and some types of → symbiotic stars. They are believed to be very → close binary systems consisting of an → accreting → white dwarf  → primary and an evolved → late-type secondary star that has filled its → Roche lobe. For systems with an → accretion disk, it is believed that a thermal instability is the cause of repetitive outbursts observed in cataclysmic variables called → dwarf novae.

cataclysmic; → variable.

Cepheid variable
  ورتنده‌ی ِ کفیءوسی   
vartande-ye Kefeusi

Fr.: variable Céphée   

A → variable star belonging to the class of → Cepheids.

Cepheid; → variable.

circular variable filter (CVF)
  پالایه‌ی ِ ورتنده‌ی ِ پرهونی، ~ ~ دایره‌ای   
pâlâye-ye vartande-ye parhuni, ~ ~ dâyereyi

Fr.: filtre circulaire variable   

Circular band-pass interference filter whose thickness and central wavelength vary along the perimeter. They are used in low-resolution spectrophotometers mainly in the infra-red.

circular; → variable; → filter.

complex dynamical variable
  ورتنده‌ی ِ توانیک ِ همتافت   
vartande-ye tavânik-e hamtâft

Fr.: variable dynamique complexe   

A → dynamical variable which has an → imaginary number part.

complex; → dynamical; → variable.

continuous variable
  ورتنده‌ی ِ پیوسته   
vartande-ye peyvasté

Fr.: variable continu   

A variable which has changes continuously, in contrast to → discrete variables.

continuous; → variable.

Delta Scuti variable
  ورتنده‌ی ِ دلتا-سپر   
vartande-ye δ-Separ

Fr.: variable δ Scuti   

A member of a class of → pulsating stars with periods less than 0.3 days, → spectral types A or F, and visual light amplitudes in the range from a few thousands of a magnitude to about 0.8 mag. On the → H-R diagram, δ Scuti stars form a group which lies in an → instability strip which includes the classical → Cepheids at its brightest end and the pulsating → white dwarfs at its faintest limit. These stars can show very complex light variations since, while some of them are pulsating in one radial mode only, others may be pulsating simultaneously in several radial and non-radial modes.

Named after the prototype star δ of constellation → Scutum; → variable.

dependent variable
  ورتنده‌ی ِ وابسته   
vartande-ye vâbasté

Fr.: variable dépendante   

Math.: A variable whose value depends on the value assigned to another value. For example, in the equation y = 2x, the value of y depends on that of x. See also → independent variable.

dependent; → variable.

differential equation with separable variables
  هموگش ِ دگرسانه‌ای با ورتنده‌های ِ جدایی-پذیر   
hamugeš-e degarsâne-yi bâ vartandehhâ-ye jodâyi-pazir

Fr.: équation différentielle à variables séparables   

A → differential equation of the form: M1(x) N1(y) dx + M2(x) N2(y) dy = 0, which can be reduced to a → differential equation with separated variables.

differential; → equation; → separate; → variable.

differential equation with separated variables
  هموگش ِ دگرسانه‌ای با ورتنده‌های ِ جدا   
hamugeš-e degarsâne-yi bâ vartandehhâ-ye jodâ

Fr.: équation différentielle à variables séparées   

A → differentail equation that can be transformed into the form: M(x)dx + N(x)dy = 0.

differential; → equation; → separate; → variable.

discrete variable
  ورتنده‌ی ِ گسسته   
vartande-ye gosasté

Fr.: variable discret   

A variable which has only → discrete values and has no in-between values.

discrete; → variable.

dynamical variable
  ورتنده‌ی ِ توانیک   
vartande-ye tavânik

Fr.: variable dynamique   

Mechanics: One of the variables used to describe a system in classical mechanics, such as coordinates (of a particle), components of velocity, momentum, angular momentum, and functions of these quantities.

dynamical; → variable.

eclipsing variable
  ورتنده‌ی ِ گرفتی   
vartande-ye gerefti

Fr.: variable à éclipses   

Same as → eclipsing binary.

eclipse; → variable.

eruptive variable
  ورتنده‌ی ِ اسدرشی   
vartande-ye osdareši

Fr.: variable éruptive   

same as → cataclysmic variable.

eruptive; → variable.

extrinsic variable star
  ستاره‌ی ِ ورتنده‌ی ِ برونگین   
setâre-ye vartande-ye borungin

Fr.: étoile variable extrinsèque   

A star whose variation in apparent brightness is not due to changes in the star itself but to some external cause, such as eclipsing by a companion.

extrinsic; → variable; → star.

hidden variable
  ورتنده‌ی ِ پنهان   
vartande-ye penhân

Fr.: variable caché   

A theory based on the hypothesis that the discrepancies with respect to classical reality found in → quantum mechanics stem from our lack of knowledge about the observed system (→ EPR paradox). According to this hypothesis, the system should be described by additional quantum parameters, of still unknown nature, but different from position, velocity, spin, etc. The hidden variable theory has been ruled out by the violation of → Bell's inequality for all theories with local property, as suggested by the → Aspect experiment.

hidden; → variable.

Hubble-Sandage variable
  ورتنده‌ی ِ هابل-سندیج   
vartande-ye Hubble-Sandage

Fr.: variable de Hubble-Sandage   

A type of highly luminous → blue supergiant star with variable light, first discovered in the M31 and M33 galaxies; also called → S Doradus stars. They are now believed to be part of the class of → Luminous Blue Variable stars.

Hubble; Allan Rex Sandage (1926-2010), American cosmologist.

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