Fr.: faible résolution
The quality of an instrument that lacks sufficient resolution for a specific observation. This is a relative quality, but presently a resolution below about 1 arcsecond.
low surface brightness galaxy (LSBG)
kahkešân bâ deraxšandegi-ye ruye-yi-ye kam
Fr.: galaxie à faible brillance de surface
A member of a particularly faint population of galaxies with a central → surface brightness below the brightness of the background sky. The central regions of many of them resemble a → dwarf galaxy, but most of the mass is contained in a large gaseous disk of low density that is observable only with long-exposure optical images or at radio wavelengths. Some are as massive as a large → spiral galaxy, for example Malin 1. The proportion of LSBGs relative to normal galaxies is unknown. They may however represent a significant fraction of mass in the Universe. LSBGs are thought to be primitive systems because they have total masses similar to normal galaxies, but have typically converted less than 10% of their gas into stars. Spiral LSBGs do not obey → Freeman's law.
owpas (#), jazr (#)
Fr.: marée basse
The state of the → tide when at its lowest level.
Fr.: marée basse
Also known as → low tide.
Fr.: neutrino faible énergie
A neutrino which is mainly produced in → nuclear processes, such as the ones in the → Sun (→ solar neutrino), or in the center of an exploding → supernova. Such neutrinos are, however, more energetic than those making up the → cosmic neutrino background.
xatt-e kamyoneš (#)
Fr.: raie de faible ionisation
A spectral line arising from a transition between atomic levels with an ionization potential below approximately 15 electron-volts.
low-ionization nuclear emission-line region
nâhiye-ye hasteyi bâ xatt-e gosili-ye kamyoneš (#)
Fr.: Noyau de galaxie à raies d'émission de faible ionisation
Same as → LINER.
Fr.: fibre à faible perte
Optical fiber that transmits a greater percentage of input light than does high-loss step-index fiber.
Fr.: galaxie de faible masse
A galaxy with stellar masses ≤ 109 → solar masses (Dawn K. Erb, 2015, Nature, 9 July).
setâre-ye kamjerm (#)
Fr.: étoile de faible masse
low-mass X-ray binary (LMXB)
dorin-e partow-e iks-e kam-jerm
Fr.: binaire X de faible masse
A member of one of the two main classes of
→ X-ray binary systems where one of the components is a
→ neutron star or → black hole
and the other component a → low-mass star with a spectral type A
or later. LMXBs mainly emit → soft X-rays.
The ratio of their optical to X-ray luminosities is less than 0.1. They belong
to → old stellar populations
with ages 5-15 × 109 years and are found in
→ globular clusters
and in the → bulge
of our → Milky Way
galaxy; some are also found in the disk.
Hercules X-1 is an example of LMXBs.
Fr.: environnement faible en métaux
A medium in which chemical elements have abundances smaller than the solar values.
Relatively low in position, rank, or order.
Comparative of → low.
havâsepehr-e zirin, javv-e ~
Fr.: atmosphère inférieure
Generally and quite loosely, that part of the atmosphere in which most weather phenomena occur (i.e., the → troposphere and lower → stratosphere); hence used in contrast to the common meaning for the → upper atmosphere. In other contexts, the term implies the lower troposphere (Meteorology Glossary, American Meteorological Society).
Fr.: culmination inférieure
The instant of culmination when the star passes between the pole and the horizon, having an hour angle of 12h. Lower culmination for non-circumpolar objects occur below the horizon and is thus unobservable. Same as → inferior culmination. See also → upper culmination.
lower main sequence
rešte-ye farist-e zirin
Fr.: séquence principale inférieure
A → main sequence star whose mass is less than 1.5 Msun. Lower main sequence stars generate their energy chiefly through the → proton-proton chain. The core is surrounded by a → radiative zone above which lies a → convective envelope. In such stars the → opacity at the surface is high because of the low → surface temperature. Therefore, radiation cannot carry all the radiation because of high opacity. Thus, energy transfer takes place by → convection to the outer layer.
Fr.: manteau inférieur
jofteš-e LS, jafsari-ye ~
Fr.: couplage LS
Same as → Russell-Saunders coupling.
Moderately warm; tepid.
M.E. lukewarme "tepid," from luke "tepid," of unknown origin, + → warm.
Velarm "lukewarm, tepid," of unknown origin.
The SI unit of luminous flux, equal to the luminous flux emitted per unit solid angle by a standard point source having a luminous intensity of 1 candela. → candela.
L. lumen (gen. luminis) "light," from lucere "to shine," related to lux "light," lucidus "clear," luna, "moon;" Fr. lumière "light;" cf. Pers. ruz "day," rowšan "bright, clear," rowzan "window, aperture;" foruq "light," afruxtan "to light, kindle;" Mid.Pers. rôšn "light; bright, luminous," rôc "day;" O.Pers. raucah-rocânak "window;" O.Pers. raocah- "light, luminous; daylight;" Av. raocana- "bright, shining, radiant;" akin to Skt. rocaná- "bright, shining," roka- "brightness, light;" Gk. leukos "white, clear;" O.E. leoht, leht, from W.Gmc. *leukhtam (cf. O.Fris. liacht, M.Du. lucht, Ger. Licht), from PIE *leuk- "light, brightness."
Lumen loanword, as above.