An Etymological Dictionary of Astronomy and Astrophysics
English-French-Persian

Mixing of two or more spectral lines of adjacent wavelengths into a broad, single line due to insufficient dispersion of the spectrograph.

→ line; → blend.

Reduction of the radiative flux in a model atmosphere due to absorption by a large number of lines. Line blocking affects the radiative transfer, ionisation and temperature structures, and the atmosphere's hydrodynamics.

→ line; block, from M.E. blok "log, stump," from O.Fr. bloc "log, block," via M.Du. bloc "trunk of a tree."

Bandâri "blocking," from band âvardan "to block," from band "dam, tie, chain," from bastan "to bind, shut, close up" (Mid.Pers. bastan, band; Av./O.Pers. band- "to bind, fetter," banda- "band, tie;" cf. Skt. bandh- "to bind, tie, fasten," bandhah "a tying, bandage;" Goth bandi "that which binds;" O.Fr. bande, bende; O.E. bend; M.E. bende; E. band; PIE base *bendh- "to bind") + âvari verbal noun of âvardan "to cause, produce; to bring" (Mid.Pers. âwurtan, âvaritan; Av. ābar- "to bring; to possess," from prefix ā- + Av./O.Pers. bar- "to bear, carry," bareθre "to bear (infinitive)," bareθri "a female that bears (children), a mother;" Mod.Pers. bordan "to carry;" Skt. bharati "he carries;" Gk. pherein; L. fero "to carry").

A widening of → spectral lines due to any of several factors, including the → Doppler broadening, → instrumental broadening, → microturbulence, → pressure broadening, → rotational broadening, the → Stark effect, and the → Zeeman effect.

→ line; → broadening.

In stellar atmosphere models, the decrease of temperature in the outer layers of atmosphere due to the escape of photons through optically thin metallic lines. Energy is transferred from the thermal pool to photons and is lost for the atmosphere, leading to a temperature decrease.

→ line; → cooling.

The process of recognizing the spectral lines in a spectrum.

→ line; → identification.

A measure of the total effect of an absorption or emission line. The line intensity is equal to the integration of the absorption coefficient over the entire shape of the absorption line.

→ line; → intensity.

Of a force, the straight line along which the force → vector is directed. The action of a force on a → rigid body does not change when its point of application is displaced along the line of action. Hence, forces applied to a rigid body can be regarded as non-localized, or sliding, vectors.

→ line; → action.

Of an elliptical orbit, the straight line drawn from the → perigee to the → apogee.

→ line, → apsides.

The intersection of the planes of ecliptic and celestial equator.

→ line; → equinox.

Same as → streamline.

→ line; → flow.

One of many → imaginary lines whose direction at all → points along its length is that of the electric or → magnetic field at those points. In → electric fields the lines of force are directed toward → negative charges and point away from → positive charges. In magnetic fields the lines of force are directed from the → north pole to the → south pole.

→ line; → force.

Same as → line of force in a magnetic field.

→ line; → induction.

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

→ line, → node.

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

→ line; → sight.

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

→ line, → profile.

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.

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

→ line, → spectrum.

Same as → line intensity.

→ line, → strength.

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.

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

→ line; → blanket; → model.