An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



Number of Results: 20 Search : magnitude
AB magnitude system
  راژمان ِ بُرز ِ BA   
râžmân-e borz-e AB

Fr.: système de magnitudes AB   

A → photometric system defined by reference to → monochromatic magnitudes in such a way that, when monochromatic → flux fν is measured in ergs sec-1 cm-2 Hz-1, the magnitude will be: AB = -2.5 logfν - 48.60. The constant is set so that AB is equal to the V magnitude for a source with a flat → spectral energy distribution. The → zero point is defined by the flux of the star → Vega at 5546 Å. In this system, an object with constant flux per unit frequency interval has zero color.

magnitude; → system.

absolute magnitude
  بُرز ِ ا َوَست   
borz-e avast

Fr.: magnitude absolue   

1) The → magnitude a star would have if it were at a distance of 10 → parsecs in a void space, without → interstellar absorption. The absolute magnitude is usually deduced from the → visual magnitude, measured through a V filter (→ UBV system), when it is written as MV. If it is defined for another wavelength, it gets another index (U, B, etc). If the radiation on all wavelengths is included, it becomes absolute → bolometric magnitude, Mbol. The Sun has the absolute magnitude + 4.8. Most of the stars have absolute magnitudes ranging between -9 (→ supergiants) and + 19 (→ red dwarfs) (M.S.: SDE).
2) The brightness a → comet or → asteroid would have if it were at a distance of 1 → astronomical unit both from the Sun and the Earth and were completely illuminated by the Sun (M.S.: SDE).

absolute; → magnitude.

apparent magnitude
  برز ِ پدیدار   
borz-e padidâr

Fr.: magnitude apparente   

A measure of a star's observed brightness (opposed to → absolute magnitude); symbol m. It depends on the star's → intrinsic brightness, its distance from the observer, and the amount of → interstellar absorption. The brightest star → Sirius has an apparent magnitude of -1.46, while the weakest stars visible with the naked eye in the most favorable observation conditions have magnitudes of about +6.5. The stars of magnitudes less than +23 are measured by professional observatories, whereas those of magnitudes less than +30 by a telescope such as the → Hubble Space Telescope (M.S.: SDE).

apparent; → magnitude.

apparent visual magnitude
  برز ِ دیدگانی ِ پدیدار   
borz-e didegâni-ye padidâr

Fr.: magnitude visuelle apparente   

Apparent magnitude in the visual wavelengths, around 5600 Å. → visual magnitude.

apparent; → visual; → magnitude.

bolometric magnitude
  برز ِ تفسنجی، ~ تفسنجیک   
borz-e tafsanji, ~ tafsanjik

Fr.: magnitude bolométrique   

The magnitude of an astronomical object for the entire range of its electromagnetic spectrum.

bolometric; → magnitude.

color-magnitude diagram
  نمودار ِ رنگ-برز   
nemudâr-e rang-borz

Fr.: diagramme couleur-magnitude   

A form of → Hertzsprung-Russell diagram in which the visual absolute magnitude Mv is the vertical axis and the → color index the horizontal axis.

color; → magnitude, → diagram.

completeness magnitude
  برز ِ اسپری   
borz-e ospori

Fr.: magnitude de complétude   

In photometric studies of a → population of astronomical objects (usually stars or galaxies), the magnitude that represents the faintest members of the population.

completeness; → magnitude.

de-reddened magnitude
  برز ِ واسرخیده   
borz-e vâsorxidé

Fr.: magnitude dérougie   

A magnitude which has been corrected for the interstellar reddening.

De-reddened, p.p. of → de-redden; → magnitude.

Borz, → magnitude; vâsorxidé p.p. of vâsorxidan, → de-redden.

eclipse magnitude
  برز ِ خورگرفت   
borz-e xorgereft

Fr.: grandeur de l'éclipse, magnitude ~ ~   

The fraction of the Sun's diameter occulted by the Moon. It is strictly a ratio of diameters and should not be confused with → eclipse obscuration, which is a measure of the Sun's surface area occulted by the Moon. Eclipse magnitude may be expressed as either a percentage or a decimal fraction (e.g., 50% or 0.50). By convention, its value is given at the instant of → greatest eclipse (F. Espenak, NASA).

eclipse; → magnitude.

instrumental magnitude
  برز ِ سازالی   
borz-e sâzâli

Fr.: magnitude instrumentale   

The magnitude derived directly using → Pogson's relation. The instrumental magnitude depends on → detectorsensitivity, telescope → aperture, exact filter → bandpass, etc. It must be → calibrated to some standard → photometric system.

instrumental; → magnitude.

integrated magnitude
  برز ِ دُرُستالیده   
borz-e dorostâlidé

Fr.: magnitude intégrée   

The magnitude an extended object (nebula, galaxy,etc.) would have if all of its light were concentrated into a point source

Integrated, p.p. of → integrate; → magnitude.

limiting magnitude
  برز ِ حد   
borz-e hadd

Fr.: magnitude limite   

The faintest magnitude reachable by an instrument.

limit; → magnitude.

  برز، قدر   
borz, qadr (#)

Fr.: magnitude   

A measure of brightness in astronomy on a → logarithmic scale in which a difference of five magnitudes represents a difference of 100 times in brightness. In this scale the lower a magnitude, the brighter the object. The faintest magnitude reached by → unaided eye is 6.

From L. magnitudo "greatness, bulk, size," from magnus "great," cognate with Pers. meh "great, large" (Mid.Pers. meh, mas; Av. maz-, masan-, mazant- "great, important," mazan- "greatness, majesty," mazišta- "greatest;" cf. Skt. mah-, mahant-; Gk. megas; PIE *meg- "great") + -tudo, suffix forming abstract nouns from adjectives and participles.

Borz "height, magnitude" (it occurs also in the name of the mountain chain Alborz), related to boland "high," bâlâ "up, above, high, elevated, height," berg "mountain, hill" (Mid.Pers. buland "high;" O.Pers. baršan- "height;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. & E. force); O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg); PIE base *bhergh- "high"). Qadr, from Ar.

magnitude scale
  مرپل ِ برز‌ها   
marpel-e borzhâ

Fr.: échelle de magnitudes   

A scale for measuring and comparing the brightness of astronomical objects.

magnitude; → scale.

magnitude-limited survey
  بردید با برز ِ حدمند   
bardid bâ borz-e haddmand

Fr.: relevé limité en magnitude   

A survey in which the observed objects are bighter than a given → apparent magnitude.

magnitude; → limited; → volume.

order of magnitude
  رایه‌یِ بُرز   
râye-ye borz

Fr.: ordre de grandeur   

Value of a number or of a physical quantity given roughly, usually expressed as a power of 10. Thus, 2.5 x 105 and 6.4 x 105 are of the same order of magnitude, and 2 x 107 is 2 orders of magnitude greater than either.

order; → magnitude.

photoelectric magnitude
  بُرز ِ شید-سنجیک، ~ نور-سنجیک   
borz-e šidsanjik, ~ nursanjik

Fr.: magnitude photoélectrique   

The magnitude of an object as measured with a photoelectric photometer.

photoelectric; → magnitude.

photographic magnitude
  بُرز ِ عکسبرداریک   
borz-e aksbardârik

Fr.: magnitude photographique   

The apparent magnitude of a star as determined by measuring its brightness on a photographic plate. The photographic magnitude scale is now considered obsolete.

Adj. of → photography; → magnitude.

photovisual magnitude
  بُرز ِ شیدچشمی   
borz-e šidcašmi

Fr.: magnitude photovisuelle   

Magnitude defined for the combination of a photographic plate and a yellow filter, approximating the spectral sensitivity of the eye.

photo- + → visual; → magnitude.

visual magnitude
  برز ِ دیدگانی   
borz-e didgâni

Fr.: magnitude visuelle   

The → apparent magnitude of a celestial body in the color sensitivity region of the human eye at a wavelength of 5600 Å. Visual magnitude is now essentially synonymous with V magnitude, which is determined photometrically.

visual; → magnitude.