1) The outer edge or border of the apparent disk of a celestial body.
→ limb brightening, → limb darkening.
From L. limbus "border, hem, fringe, edge," cognate with Skt. lambate "hangs down."
Labé "limb, edge," from lab "lip;" Mid.Pers. lap; cognate with L. labium, E. lip; Ger. Lefze.
Fr.: embrillancement centre-bord
An observed increase in the intensity of radio, extreme ultraviolet, or X-radiation from the Sun from its center to its limb.
Fr.: assombrissement centre-bord
An apparent decrease in brightness of the Sun near its edge as compared to its brightness toward the center. Limb darkening is readily apparent in photographs of the Sun. The reason is that when we look toward the disk's center we look into deeper and hence hotter layers along the line of sight. Toward the limb, we get radiation from higher and hence cooler and less bright layers of the → photosphere. Limb darkening has been detected in the case of several other stars. A similar phenomenon occurs in → eclipsing binaries where the effect of limb darkening on one or both components manifests itself in the shape of the system's → light curve.
A white or grayish-white substance obtained by burning → limestone, used in mortars, plasters, cements, and in the manufacture of steel, paper, glass, and various chemicals of calcium.
M.E., O.E. lim; akin to Du. lijm, Ger. Leim, O.N. lim "glue;" L. limus "slime."
Âhak, probably a variant of xâk, → soil.
sang-e âhak (#)
Fr.: castine, calcaire
A → sedimentary rock composed principally of calcium carbonate. Limestone is usually formed from shells of once-living organisms or other organic processes, but may also form by inorganic precipitation.
1) General: The final, utmost, or furthest → boundary or
→ point as to extent, amount, continuance, procedure, etc.
From O.Fr. limite "a boundary," from L. limitem (nom. limes) "a boundary, embankment between fields, border," related to limen "threshold."
Loan from Ar. Hadd "limit, term."
Confined within limits; restricted or circumscribed.
Adj. of → limit.
Fr.: magnitude limite
The faintest magnitude reachable by an instrument.
A widely occurring ore of yellowish-brown to black color that consists of amorphous oxides of iron.
Gk. leimon "meadow" in reference to its occurrence as "bog ore" in meadows and marshes + → -ite.
Fr.: résonance de Lindblad
A kinematic resonance hypothesized to explain the existence of galactic → spiral arms. It occurs when the frequency at which a star encounters the spiral → density wave is a multiple of its → epicyclic frequency. Orbital resonances occur at the location in the disk where Ωp = Ω ± κ/m, where Ωp is → pattern speed, κ → epicyclic frequency, and m an integer representing the number of spiral arms. The minus sign corresponds to the inner Lindblad resonance (ILR) and the plus sign to the outer Lindblad resonance (OLR). The corotation resonance corresponds to Ωp = Ω. In general, the Lindblad resonances are defined for two spiral arms (m = 2), and low order. There are other less important resonances corresponding to higher m values. These resonances tend to increase the object's orbital eccentricity and to cause its longitude of periapse to line up in phase with the perturbing force. Lindblad resonances drive spiral density waves both in galaxies (where stars are subject to forcing by the spiral arms themselves) and in Saturn's rings (where ring particles are subject to forcing by Saturn's moons).
After the originator of the model, Bertil Lindblad (1895-1965), a Swedish astronomer, who made important contributions to the study of the rotation of the Galaxy; → resonance.
xatt (#), xat (#)
1) A mark or stroke long in proportion to its breadth, made with a pen, pencil,
or other tools.
M.E. li(g)ne "cord, rope, stroke, series," from O.E. line "rope, row of letters," partly from O.Fr. ligne, from L. linea "linen thread, string, line," from phrase linea restis "linen cord," from fem. of lineus (adj.) "of linen," from linum "flax, linen."
Xatt, xat, used also in Ar., but it has no Hebrew counterpart. Xat is probably of Iranian origin, from *kerš-/*xrah- "to draw, plow;" cf. Av. karš- "to draw; to plow," karša- "furrow;" Mid/Mod.Pers. kešidan, kašidan "to draw, protract, trail, drag, carry," dialectal Yaqnavi xaš "to draw," Qomi xaš "streak, stria, mark," Lori kerr "line;" cf. Skt. kars-, kársati "to pull, drag, plow;" Gk. pelo, pelomai "to move, to bustle;" PIE base kwels- "to plow."
In stellar atmosphere models, the effect of metallic lines on the atmospheric structure of stars. The additional opacities of thousands of metallic lines alter the radiative transfer, leading to changes in the temperature. The emergent spectrum is consequently modified.
Fr.: confusion de raies
Mixing of two or more spectral lines of adjacent wavelengths into a broad, single line due to insufficient dispersion of the spectrograph.
Fr.: blocage par raies
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").
Fr.: élargissement de raie
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.
Fr.: refroidissement dû aux raies
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.
Fr.: identification de raies
The process of recognizing the spectral lines in a spectrum.
Fr.: intensité de raie
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 of action
xatt-e žireš, ~ koneš
Fr.: ligne d'action
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 of apsides
Fr.: ligne des apsides