An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 1381

Fr.: spécifité   

The state or character of being → specific.

specific; → -ity.

  ۱) پرسونیدن؛ ۲) آبیزیدن   
1) parsunidan; 2) âbizidan

Fr.: préciser, spécifier   

1) To mention or name specifically or definitely; state in detail.
2) To give a specific character to; to set forth as a specification (

specific; → -fy.

nemuné (#)

Fr.: specimen   

A part or an individual taken as exemplifying a whole mass or number; a typical animal, plant, mineral, part, etc. → sample.

From L. specimen "mark, example, indication, sign, evidence," from speci- stem of specere "to look at," → -scope, + -men noun suffix denoting result or means.

Nemuné, from nemudan "to show;" Mid.Pers. nimūdan, nimây- "to show," from O.Pers./Av. ni- "down; in, into," → ni- (PIE), + māy- "to measure;" cf. Skt. mati "measures," matra- "measure;" Gk. metron "measure;" L. metrum; PIE base *me- "to measure."


Fr.: tavelure   

1) Optics: An image defect, one of a large number of bright and dark spots, that appears when an object is illuminated by monochromatic, highly → coherent light. This phenomenon results from the → interference of a number of randomly phased complex contributions of electromagnetic → wavefronts scattered from an object with rough structure, such as a piece of paper, a display screen, or a metallic surface. In particular, whenever the object is rough on the scale of an optical wavelength, the image has a grainy appearance. Also called speckle noise.
2) Astro.: The pattern produced by a short-exposure image of a → point source, such as a star, when the → wavefront is torn apart under the effect of the → atmospheric turbulence. Speckles change very rapidly with time as a function of the atmospheric turbulence. → speckle lifetime. Long exposure images of these changing speckle patterns result in a blurred image of the star, called a → seeing disk. → Fried parameter.

Speckle "a speck or small spot, as a natural dot of color on skin, plumage, or foliage," from M.E.speck (from O.E. specca "small spot, stain," of unknown origin; probably related to Du. speckel "speck, speckle") + -le a noun suffix having originally a diminutive meaning.

Pakâl, from pak "spot" (Lâri, Gerâši), pašy "mingled, confused" (Tâleši), probably related to pisé "dappled, variegated," pis, pisi "leprosy," neveštan "to write," pišé "profession," → professional astronomer; Mid.Pers. parš "speckled, spotted," pēsīdan "to color, adorn," pēsit "adorned;" O.Pers. pais- "to adorn, cut, engrave;" Av. paēs- "to paint, adorn," paēsa- "adornment;" cf. Skt. peś- "to adorn, hew out, decorate," piśáti "adorns; cuts;" Gk. poikilos "multicolored;" L. pingit "embroiders, paints;" O.C.S. pisati "to write;" O.H.G. fēh "multicolored;" Lith. piēšti "to draw, adorn;" PIE base *peik- "colored, speckled."

speckle interferometry
  اندرزنش‌سنجی ِ پَکال   
andarzaneš-sanji-ye pakâl

Fr.: interférométrie des tavelures   

A technique for generating a clear composite image of a celestial object blurred by → atmospheric turbulence in which a large number of short-exposure photographs are mathematically correlated by a computer. By comparing the behavior of the → speckles in a series of images it is possible to approach the theoretical resolution of the telescope.

speckle; → interferometry.

speckle lifetime
  عمر ِ پَکال   
omr-e pakâl

Fr.: durée de vie de tavelures   

The time scale on which a stellar image changes significantly due to → atmospheric turbulence. It is proportional to the ratio r0/Δv, where r0 is the → Fried parameter and Δv the standard deviation of the distribution of wind velocities weighted by the turbulence structure coefficient. Typical lifetimes in the visible range from about 3 to 30 milliseconds.

speckle; → life; → time.

Omr "life-time;" from Ar. 'umr; pakâl, → speckle.

speckle noise
  نوفه‌ی ِ پکال   
nufe-ye pakâl

Fr.: bruit de tavelures   

An image defect associated with the → speckle phenomenon.

speckle; → noise.

binâbi (#)

Fr.: spectral   

Of or pertaining to a → spectrum.

spectrum; → -al.

spectral classification
  رده‌بندی ِ بینابی   
radebandi-ye binâbi (#)

Fr.: classification spectrale   

A system that assigns a → spectral type to a star according to characteristics of its spectrum. The earliest attempt to divide stars on the basis of their spectra was the → Secchi classification in the 1860s. This scheme paved the way for the → Harvard classification that led to the current → Morgan-Keenan classification of spectral types. In the Harvard system stars were originally thought to follow an evolutionary sequence from the "early" O and B types to the "late" K and M types. Although this is now known to be wrong, the terms → early-type star and → late-type star are still in use. In the Morgan-Keenan system stars are classified as type O, B, A, F, G, K, or M in order of decreasing → effective temperature, and each type further subdivided into subclasses from 0 (hottest, except for → O-type stars) to 9 (coolest). They are also accompanied by a → luminosity class. In the late 1990s, spectral types L and T were added to the sequence to accommodate the coolest stars and → brown dwarfs (with class Y reserved for the coolest brown dwarfs of all, as yet unobserved).

spectral; → classification.

spectral coverage
  پوشش ِ بینابی   
pušeš-e binâbi

Fr.: couverture spectrale   

The → range of → wavelengths or frequencies (→ frequency) at which a → detector is sensitive. Same as → bandwidth.

spectral; → coverage.

spectral density
  چگالی ِ بینابی   
cagâli-ye binâbi

Fr.: densité spectrale   

For a specified → bandwidth of radiation consisting of a continuous → frequency spectrum, the total → power in the bandwidth divided by the bandwidth. Spectral density describes how the power (or variance) of a time series is distributed with frequency. Also called power spectral density.

spectral; → density.

spectral dispersion
  پاشش ِ بینابی   
pâšeš-e binâbi

Fr.: dispersion spectrale   


spectral; → dispersion.

spectral energy distribution (SED)
  واباژش ِ کاروژ ِ بینابی   
vâbâžeš-e kâruž-e binâbi

Fr.: distribution de l'énergie spectrale   

A plot showing the energy emitted by a source as a function of the radiation wavelength or frequency. It is used in many branches of astronomy to characterize astronomical sources, in particular mainly in → near infrared and → middle infrared to study → protostars or → young stellar objects. The SED of these objects is divided in four classes.
Class 0 in which the SED represents a very embedded protostar, where the mass of the central core is small in comparison to the mass of the → accreting envelope. The SED is characterized by the → blackbody radiation of the envelope and peaks at → submillimeter wavelengths.
Class I objects possess a SED that peaks in the → far infrared and is characterized by a weak contribution of the blackbody of the central protostar (detected in near infrared) and the emission of a thick disk and dense envelope. These objects have less mass in the envelope and more massive central cores with respect to Class 0.
Class II objects are the → classical T Tauri stars with a SED due to the emission of a thin disk and the central star. They have accumulated most of their final mass and have dispersed almost completely their circumstellar envelope.
Finally, Class III objects have pure photospheric spectra. Their SED is peaked in the optical and is well approximated by a blackbody emission with a faint → infrared excess due to the presence of a residual optically thin disk that may be the origin of → planetesimals.
This classification scheme can be made more quantitative by defining a → spectral index.

spectral; → energy; → distribution.

spectral feature
  آرنگ ِ بیناب، ~ بینابی   
ârang-e binâb, ~ binâbi

Fr.: motif spectral   

An emission or absorption mark in the spectrum of an astronomical object, of known or unknown origin, usually with complex structure.

spectral; → feature.

spectral index
  دیشن ِ بینابی   
dišan-e binâbi

Fr.: indice spectral   

1) The → exponent of the → frequency on which depends the intensity of the → continuum emission, that is: Fν∝ να. The exponent (α) typically takes positive values from 0 to 2 for → thermal emission, while → non-thermal emission, such as → synchrotron radiation, leads to negative values of the spectral index ranging from about -0.5 to -1.5.
2) The ratio αIR = dlog(λFλ)/dlogλ, where F represents the flux and λ the wavelength, in the range 2.2 μm ≤ λ ≤ 25 μm, particularly used in the classification of → protostars (→ Class I, → Class II, and → Class III).

spectral; → index.

spectral line
  خطّ ِ بینابی   
xatt-e binâbi

Fr.: raie spectrale   

A dark or bright line in an otherwise uniform and continuous spectrum, resulting from an excess or deficiency of photons in a narrow wavelength range, compared with the nearby wavelengths.

spectral; → line.

spectral range
  گستره‌ی ِ بینابی   
gostare-ye binâbi

Fr.: domain spectral   

The observable spectral range provided by a spectroscope, as determined by the grating dispersion, camera focal length, and detector size.

spectral; → range.

spectral region
  ناحیه‌ی ِ بینابی   
nâhiye-ye binâbi

Fr.: région spectrale   

An extent of wavelengths into which the electromagnetic spectrum is divided; e.g. infrared or ultraviolet region.

spectral; → region.

spectral resolution
  واگشود ِ بیناب، ~ بینابی   
vâgošud-e binâb, ~ binâbi

Fr.: résolution spectrale   

The capacity of a spectrograph to separate two adjacent spectral lines. The theoretical spectral resolution depends on the grating dispersion, grating position, pixel size, collimator and camera focal length, and the entrance slit-width.

spectral; → resolution.

spectral response
  پاسخ ِ بینابی   
pâsox-e binâbi

Fr.: réponse spectrale   

Domain of the electromagnetic spectrum over which a detector is sensitive. Same as spectral sensitivity.

spectral; → response.

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