An Etymological Dictionary of Astronomy and Astrophysics

فرهنگ ریشه شناختی اخترشناسی-اخترفیزیک

M. Heydari-Malayeri    -    Paris Observatory



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Number of Results: 174 Search : line
quasi-linear theory
  نگره‌ی ِ چونان-خطی   
negare-ye cunân-xatti

Fr.: théorie quasi-linéaire   

In plasma physics, the theory that considers the interactions between waves and particles are of first order only. It ignores all terms of second order in the fluctuating quantities.

quasi-; → linear; → theory.

radio recombination line
  خط ِ بازمیازش ِ رادیویی   
xatt-e bâzmiyâzeš-e râdioyi

Fr.: raie de recombinaison radio   

A → recombination line whose wavelength lies in the radio range of the electromagnetic spectrum. Radio recombination lines are the result of electronic transitions between high energy levels (n > 50) in an atom or ion.

radio; → recombination line.

Rayleigh line
  خط ریلی   
xatt-e Rayleigh

Fr.: 1) droite de Rayleigh; 2) raie de Rayleigh   

1) A straight line that connects the points corresponding to the initial and final states on a graph of pressure versus specific volume for a substance subjected to a → shock wave. The slope of the Rayleigh line is proportional to the square of shock speed. Steeper Rayleigh lines correspond to higher shock speeds. See also → Hugoniot curve.
2) In → Raman scattering, the spectral line in scattered radiation which has the same frequency as the corresponding incident monochromatic radiation.

rayleigh; → line.

recombination line
  خط ِ بازمیازش   
xatt-e bâzmiyâzeš

Fr.: raie de recombinaison   

An → emission line in a spectrum produced in an → H II region when a free electron combines with an ionized atom to form a neutral atom or an ion of lower → ionization stage. Same as → free-bound emission.

recombination; → line.

râst-xatt (#)

Fr.: rectiligne   

In a straight line; consisting of straight lines. → curvilinear

From recti- combining form of rectus, → right, + → line + -ar, variant of the adjective-forming suffix → -al.

Râst-xatt, from râst, → right, + xattline.

rectilinear propagation of light
  توچش ِ راست‌خط ِ نور   
tuceš-e râst-xatt-e nur

Fr.: propagation rectiligne de la lumière   

The motion of light in the first approximation, as evidenced from the formation of shadows and other every day experience. However, → diffraction

rectilinear; → propagation; → light.

rectilinear system
  راژمان ِ راست‌خط   
râžmân-e râst-xatt

Fr.: système rectilinéaire   

An optical system that is corrected for → distortion and → spherical aberration and therefore forms the image of a straight line as a straight line.

rectilinear; → system.

redshifted line
  خط ِ سرخ‌کیبیده   
xatt-e sorx kibideh

Fr.: raie décalée vers le rouge   

A spectral line whose wavelength does not coincide with its theoretical value and is shifted toward longer wavelengths.

red; → shift; → line.

regression line
  خط ِ وایازش   
xatt-e vâyâzeš

Fr.: droite de régression   

The curve representing a → linear regression. It is a line drawn through a set of data that summarizes the relationship between the → variables being studied.

regression, → line.

resolved line
  خط ِ واگشوده   
xatt-e vâgošudé

Fr.: raie résolue   

A → spectral line that is not contaminated by other nearby lines.

resolved; → line.

resonance line
  خط ِ باز‌آوایی   
xatt-e bâzâvâyi

Fr.: raie de résonance   

For a particular atom, the spectral line corresponding to the longest wavelength arising from a transition between the ground state and an excited state.

resonance; → line.

satellite line
  خط ِ بنده‌وار   
xatt-e bandevâr

Fr.: raie satellite   

Radio astro.: Of an OH source, which emits at 1665 and 1667 MHz as the main frequencies, one of the lines arising from transitions at 1612 and 1730 MHz.

satellite; → line.

semi-forbidden line
  خط ِ نیمه-بژکم   
xatt-e nime-bažkam

Fr.: raie semi-interdite   

A → spectral line for which the upper and lower → energy levels have different values of S, the total → spin angular momentum. These lines violate the quantum mechanical → selection rule under → LS coupling, ΔS = 0. For example, the Ca I λ6573 line results from transition between the upper → triplet state (3P1) with a total spin angular momentum S = 1 and the → ground state, a → singlet state (1S0, total spin angular momentum S = 0). A semi-forbidden line is marked by a right bracket following the atom name, i.e. Ca I], in the above-mentioned case. Same as → interconnection line and → intersystem line.

semi-; → forbidden; → line.


Fr.: ligne de visée   

line of sight.

sight; → line.

single-lined binary
  دُرین ِ تک-خطه   
dorin-e tak-xatté

Fr.: binaire à une seule raie   

A → spectroscopic binary in which only one set of → spectral lines is detectable. The binary nature of the system is deduced from the fact that the spectral lines exhibit periodic → Doppler shifts due to orbital motions in the system. Same as → SB1 binary. See also: → double-lined binary.

single; → line; → binary.

snow line
  مرز ِ یخ، یخ-مرز   
marz-e yax, yax-marz

Fr.: limite de glace   

In a → protoplanetary disk, the limit between the regions where water is gaseous and the region where it is cold enough for water to become ice. The core accretion theory predicts that → giant planets form just outside the snow line where they can accrete enough rock and ice to generate a core. Subsequently the core grows into a gas giant like → Jupiter or → Saturn via the → accretion of hydrogen and helium. The snow line location depends on the → luminosity of the central star. For solar system it is about 5 AU, the position of Jupiter. Also known as ice line.

snow; → line.

Marz, → frontier; yax, → ice.

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.

spline function
  کریای ِ اسپلین   
karyâ-ye splin

Fr.: fonction spline   

A function consisting of several segments, usually → polynomials, joined smoothly together at specific points with an explicitly stated degree of accuracy. Spline functions are used to approximate a given function on an interval.

From East Anglian dialect, maybe related to O.E. splin and to modern splint. A spline was originally a slat or a thin strip of wood. A later meaning was "a long, thin, flexible strip used as a guide for drawing arcs of curves;" → function.

straight line
  خط ِ راست   
xatt-e râst (#)

Fr.: droite   

A line without curvature or angles. A line whose → slope is → constant.

straight; → line.

streak line
  خط ِ خش   
xatt-e xaš

Fr.: ligne d'émission   

In → fluid mechanics, the curve defined by the positions of all particles which have passed through a given point. In laboratory experiments, streak line may be displayed by the stream of color resulting from injection of a dye into the flow.

streak; → line.

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