blue horizontal branch star
setâre-ye âbi-ye šâxe-ye ofoqi
Fr.: étoile bleue de la branche horizontale
A member of a population of blue stars appearing on the → horizontal branch in the → Hertzsprung-Russell diagram of the Galactic → halo populations and → globular clusters. Belonging to → spectral types B3 to A0, they have evolved past the → red giant stage and are burning helium in their core.
Fr.: jet bleu
A transient optical phenomenon in the → stratosphere that emerges from the tops of → thunderstorm clouds at tremendous speeds. As their name implies, blue jets are optical ejections from the top of the electrically active core regions of thunderstorms. Following their emergence, they typically propagate upward in narrow cones at vertical speeds of roughly 100 km/s, fanning out and disappearing at heights of about 40-50 km. See also → sprite; → elve.
Fr.: fuite bleue
Leakage phenomenon in a filter, causing an unwanted response to the blue or green light.
→ blue; leak, from M.Du. leken "to drip, to leak," or from O.N. leka, cognate of O.E. leccan "to moisten," from P.Gmc. *lek- "deficiency" (cf. O.H.G. lecchen "to become dry," Ger. lechzen "to be parched with thirst").
Našt "leak," origin unknown; âbi, → blue.
Fr.: boucle bleue
An evolutionary behavior of certain stars, particularly massive stars, which return to the blue stage after becoming a red supergiant. The phenomenon appears as a blueward loop on the theoretical evolutionary tracks.
Fr.: lune bleue
The second full moon in a calendar month. For a blue moon to occur, the first of the full moons must appear at or near the beginning of the month so that the second will fall within the same month. Full moons are separated by 29 days, while most months are 30 or 31 days long; so it is possible to fit two full moons in a single month. This happens every two and a half years, on average.
The folkloric term blue Moon for the calendrical event is new, and apparently goes back to the Maine Farmers' Almanac for 1937. But its original meaning in that work was the third full Moon in a season when there were four full Moons in that season. Some have related the term to the much older English expression moon is blue, which goes back to a couplet from 1528, interpreting it as "something that occurs rarely." However in that poem the expression had a meaning of "something that was absurd." Alternatively, the term blue Moon may have been borrowed from the Chinese lunar calendar particularly in its usage among American Chinese community. In fact in that calendar when there are two full Moons in a month they use the term "blue Moon" and add a thirteenth intercalary month. → blue; → moon.
Fr.: région bleue
The portion of the → visible spectrum lying between 455 and 492 nm.
âsmân-e âbi (#)
Fr.: ciel bleu
A phenomenon which results from → Rayleigh scattering of sunlight by → atmospheric molecules. → Nitrogen and → oxygen molecules that compose about 78% and 21% of the air, respectively, are small compared to the light → wavelengths, and thus more effective at scattering shorter wavelengths of light (blue and violet). The → selective scattering by these → molecules is responsible for producing the blue skies on a clear sunny day. The sky over the horizon appears much paler in color, because the scattered blue light must pass through more air. Some of it gets scattered away again in other directions. Hence, less blue light reaches the observer's eyes.
Fr.: traînarde bleue, traînard bleu
Any of stars, often found in → globular clusters and old → open clusters, that lie on the blueward extension of the → main sequence beyond the → turnoff point. Blue stragglers have an anomalously blue color and high luminosity in comparison with other cluster members. The most probable ways in which they could form are: → mass transfer or → coalescence in → close binary systems, encounters or collisions in overcrowded cores of globular clusters.
Fr.: supergéante bleue
Fr.: aile bleue
The → line wing with wavelengths shorter than that of the emission or absorption peak.
Fr.: décalage vers le bleu
The apparent shift of the wavelength towards the shorter wavelength region of the radiation spectrum of an approaching object due to the Doppler effect.
Fr.: composante décalée vers le bleu
A constituent of a composite astronomical object which has a motion directed towards the observer, as revealed by its spectrum.
1) (v.tr.) To make indistinct and hazy in outline or appearance.
Probably akin to M.E. bleren "to blear."
Târ "dark, obscure, cloudy" Mid.Pers. târ, from Mid./Mod.Pers. târ "dark, obscure, cloudy."
tasvir-e târ, ~ nâtig
Fr.: image estompée, ~ floue
In → galactic dynamics models, the → scattering of stars at radii substantially away from → corotation resonance, especially at the → Lindblad resonances, leading to a higher → eccentricity. The → spiral wave response of a → galactic disk to a co-orbiting mass → clump blurs the distinction between scattering by → spiral arms and by mass clumps. See also → churning (J. A. Sellwood & J. J. Binney, 2002, astro-ph/0203510 and references therein).
Verbal noun of → blur.
The Herdsman, the Ox Driver. A constellation in the northern hemisphere, at right ascension about 14h 30m, north declination about 30°. Its brightest star is → Arcturus. Abbreviation: Boo; genitive form: Boötis.
L. Boötes, from Gk. bootes "plowman," literally "ox-driver," from bootein "to plow," from bous "ox," from PIE *gwou- "ox, bull, cow;" compare with Av. gao-, gâuš "bull, cow, ox," Mod.Pers. gâv, Skt. gaus, Armenian kov, O.E. cu.
Gâvrân "ox-driver," from gâv "ox, cow" + rân
"driver," from rândan "to drive."
Fr.: loi de Bode
1) tan; 2) jesm (#)
1) The physical structure of a human being or animal, including the bones, flesh,
Body, from O.E. bodig "trunk, chest," related to O.H.G. botah, of unknown origin.
1) Tan, from Mid.Pers. tan "body, person;"
O.Pers. tanūš "body," tanūm [acc.sg.] "(to) oneself;"
Av. tanū- "body, person, self," tanūm [acc.sg.];
cf. Skt. tanūš- "body, self;" PIE base *ten-uh- "body."
Fr.: classification de Boeshaar-Keenan
A system for the classification of → S-type stars. The system involves the designations of a C/O index and a temperature type. Moreover, when possible, it uses intensity estimates for → ZrO bands, the → TiO bands, the → Na I D-lines, the YO bands, and the Li I 6708 line.
Philip C. Keenan & Patricia C. Boeshaar, 1980, ApJS, 43, 379; → classification.
Niels Bohr (1885-1962), Danish physicist who made several important contributions to modern physics. He won the 1922 Nobel prize for physics in recognition of his work on the structure of atoms.