An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 464
line of nodes
  خط ِ گره‌ها   
xatt-e gerehhâ (#)

Fr.: lignes des nœuds   

The line created by the intersection of the equatorial plane and the orbital plane.

line, → node.

line of sight
  خط ِ دید، دیدخط   
xatt-e did, didxatt (#)

Fr.: ligne de visée   

The imaginary straight line connecting the object and the objective lens of the viewing device.

line; → sight.

line profile
  فراپال ِ خط   
farâpâl-e xatt

Fr.: profil de raie   

The representation of a spectral line as produced by an observing instrument.

line, → profile.

line profile variability (LPV)
  ورتندگی ِ فراپال ِ خط   
vartandegi-ye farâpâl-e xatt

Fr.: variabilité du profil de raie   

The change in the shape of a → spectral line over time. For instance, in → Wolf-Rayet stars the line profile varying on time-scales of minutes to hours is attributed to → microturbulence.

line; → profile; → variability.

line spectrum
  بیناب ِ خطی   
binâb-e xatti (#)

Fr.: spectre de raies   

Spectrum consisting of discrete lines (emission or absorption), each corresponding to a particular wavelength, as opposed to a continuous spectrum.

line, → spectrum.

line strength
  زور ِ خط   
zur-e xatt

Fr.: intensité de raie   

Same as → line intensity.

line, → strength.

line wing
  خط-بال، بال ِ خط   
xatbâl, bâl-e xatt

Fr.: aile de raie   

Part of the line profile between the continuum level and the half value of the emission or absorption peak. The wings are due to matter traveling at much greater speeds than that providing the main peak. → red wing; → blue wing.

line; → wing.

line-blanketed model
  مدل ِ پتومند   
model-e patumand


A stellar atmosphere model which includes metals or uses methods to reproduce their effects, → line blanketing.

line; → blanket; → model.

line-driven wind
  باد ِ خط‌زاد   
bâd-e xattzâd

Fr.: vent induit par raie   

Same as → radiation-driven wind.

line; → drive; → wind.


Fr.: ligne   

Any of a countless number of dark streaks visible on → Europa's surface that crisscross the whole → Galilean satellite. They are up to 1,000 km long, 20 km wide, and 1 km deep, but only hundred of meters high. In many cases, the ridges are double, often with dark outer edges and a central band. Images show that on each side of the lines, the edges have moved relative to each other. According to the most likely hypothesis, lineae result from eruptions of warm water, in a scenario similar to the present day mid- oceanic ridges on Earth.

From L. linea, → line.

Xaš, → streak.

xatti (#)

Fr.: linéaire   

Confined to first-degree algebraic terms in the relevant variables.

Adj. of → line.

linear approximation
  نزدینش ِ خطی   
nazdineš-e xatti

Fr.: approximation linéaire   

Taking the first term in the Taylor series as an approximation to a mathematical function at a given point. → first approximation.

linear; → approximation.

linear astrolabe
  اسطرلاب ِ خطی   
ostorlâb-e xatti

Fr.: astrolabe linéaire   

A version of → planispheric astrolabe in which the → celestial sphere and the various circles of altitude and declination are projected on to a line represented by a staff. The staff is equivalent to the meridian line and contains markings to indicate the centers of these circles and their intersections with the meridian. By attaching three ropes to the appropriate points on the staff to act as radii, the circles and their intersections can be reconstructed. One of the ropes was attached to a plumb line. A scale giving chord lengths in the meridian circle extended the linear astrolabe's range of applications. It was invented by the Iranian mathematician and astronomer Sharafeddin Tusi (c1135-1213), but no early example has survived. Same as → Sharafeddin's staff and Tusi's staff.

linear; → astrolabe.

linear correlation
  هم‌باز‌آنش ِ خطی   
hambâzâneš-e xatti

Fr.: corrélation linéaire   

A measure of how well data points fit a straight line. When all the points fall on the line it is called a perfect correlation. When the points are scattered all over the graph there is no correlation.

linear; → correlation.

linear diameter
  ترامون ِ خطی   
tarâmun-e xatti

Fr.: diamètre linéaire   

The real physical diameter, as opposed to angular diameter.

linear; → diameter.

linear differential equation
  هموگش ِ دگرسانه‌ای ِ خطی   
hamugeš-e degarsâne-yi-ye xatti

Fr.: équation différentielle linéaire   

An equation in which the → dependent variable y and all its differential coefficients occur only in the first degree. A linear differential equation of → order  order n has the form:
fn(x)y(n) + fn-1(x)y(n-1) + ... + f1(x)y' + f0(x)y = Q(x),
where f0(x), f1(x), ..., fn(x) and Q(x) are each continuous functions of x defined on a common interval I and fn(x)≠ 0 in I. A linear differential equation cannot have, for example, terms such as y2 or (y')1/2. See also: → homogeneous linear differential equation; → nonhomogeneous linear differential equation.

linear; → differential; → equation.

linear equation
  هموگش ِ خطی   
hamugeš-e xatti

Fr.: équation linéaire   

An equation composed of first degree variables and representing a straight line.

linear; → equation.

linear function
  کریای ِ خطی   
karyâ-ye xatti

Fr.: fonction linéaire   

A function expressed by a → first degree equation that can be graphically represented in the → Cartesian coordinate plane by a → straight line.

linear; → function.

linear instability
  ناپایداری ِ خطی   
nâpâydâri-ye xatti (#)

Fr.: instabilité linéaire   

An instability that can be described (to first-order accuracy) by linear (or tangent linear) equations.

linear; → instability.

linear momentum
  جنباک ِ خطی   
jonbâak-e xatti

Fr.: quantité de mouvement linéaire   

The product of an object's → mass and → velocity. It is a → vector and points in the same direction as the velocity vector. Linear momentum is distinguished from → angular momentum. When there is no opportunity for confusion, usually the term momentum is used instead of linear momentum.

linear; → momentum.

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