Fr.: zone de Brillouin
Crystallography: One of the several regions which, in reciprocal space, represent the solution of the wave equations for the propagation of → phonons or electrons in solids. The first Brillouin zone is the Wigner-Seitz cell of the reciprocal lattice. It is a polyhedron obtained by connecting a lattice point to its first neighbors and drawing the planes perpendicular to these connecting lines and passing through their midpoints. The second Brillouin zone is obtained by a similar construction but the second-nearest neighbours.
After Léon Brillouin (1889-1969) French physicist; → zone.
1) Water saturated or strongly impregnated with salt.
M.E. from O.E. bryne "brine," origin unknown; cognate with Du. brijn.
Aždem, from Gilaki and Tâti aždem "very salty water" used for preserving fish.
Fr.: cassant, friable
M.E. britel, from brit-, akin to O.E. brytan "to crush, break to pieces," + -el adj. suffix.
Tord "brittle, fragile;" ultimately from Proto-Ir. *tard- "to split, pierce;" related to tâlidan (Dehxodâ) "to spoliate, plunder," eftâlidan "to tear, break," → dissipate; cf. Shughni tidarδ- "to tear, pluck," zidarδ- "to tear, break;" Skt. tard- "to split, to pierce."
Wide in extent from side to side.
M.E. bro(o)d, from O.E. brad; cf. O.N. breiðr, Du. breed, Ger. breit, Goth. brouþs.
Pahn "wide, broad," from Mid.Pers. pah(a)n; Av. paθana- "broad, wide, spacious;" PIE root *pete- "to spread;" cf. L. patere "to be open," Gk. petannynai "to spread out," petalon "a leaf."
Fr.: photométrie à bande large
Photometric measurements carried out through filters with a band-width (about one-tenth the central wavelength) in the range 30-100 nm. Typical examples are Johnson photometry, Krons-Cousins RI photometry, and the six-color system.
broad-line radio galaxy (BLRG)
radio kahkašân-e pahn-xatt
Fr.: galaxie radio à raies larges
A radio galaxy that shows broad optical emission lines. → broad-line region.
broad-line region (BLR)
Fr.: région à raies larges
The inner region of a → quasar or an → active galactic nucleus exhibiting broad → spectral lines which indicate ionized matter moving with speeds in excess of 10,000 km sec-1, probably due to the presence of an → accretion disk surrounding a → supermassive black hole. Also called Type I AGN. See also → obscuring torus.
To make or become broad or broader.
Pahnidan, from pahn, → broad, + -idan infinitive suffix.
Pahneš, from pahn (→ broad, present tense stem of pahnidan "to broaden" + -idan infinitive suffix) + eš verbal-noun suffix.
Fr.: amas de Brocchi
Same as the → Coathanger and Collinder 399.
Named after the American amateur astronomer D. F. Brocchi who created a map of the cluster in the 1920s for calibrating photometers; → cluster.
xatt-e šekasté (#)
Fr.: ligne brisée
A system of connected line → segments joined end to end.
The only liquid non-metallic chemical element; symbol Br. → Atomic number 35; → atomic weight 79.904; → melting point -7.2°C; → boiling point 58.78°C; → specific gravity of liquid 3.12 at 20°C; → valence -1, +1, +3, +5, or +7. A member of the halogen group of elements. Volatilizes readily at room temperature to a red vapor with strong disagreeable odor and very irritating effect on the eyes and throat. Occurs in combination with various metals, as potassium, sodium and magnesium bromides, which are found in mineral waters, in river and sea-water, and occasionally in marine plants and animals. Its compounds are widely used in photography and medicine. Discovered by Antoine-Jerome Balard (1802-1876) in 1826. Its two stable → isotopes are 79Br (50.69%) and 81Br (49.31%).
From Fr. brome, from Gk. bromos for "stench, bad odor," coined by its discoverer.
Brom, loan from Fr., as above.
boronz (#), mefraq (#)
A class of → alloys in which → copper and → tin are the dominant elements. The name is extended by usage to include many other copper-rich alloys containing → phosphorus, → manganese, → aluminium, or → silicon.
From Fr. bronze, from It. bronzo, from M.L. bronzium, of unknown origin, maybe from Iranian, cf. Mid.Pers. brinj "bronze, brass;" Mod.Pers. berenj "brass."
Boronz, loan from Fr., as above. Mefraq, from Ar.
asr-e boronz (#)
Fr.: âge du fer
A period of time between the → Stone Age and the → Iron Age when bronze was used widely to make tools, weapons, and other implements. The Bronze Age starts at different areas of the world at different times. The earliest use of bronze for making farm tools and weapons are found in Near and Middle East and date back to about 3700 BC. The Bronze Age starts about 2300 BC in Europe.
Son of the same parents as another person.
Barâdar, from Mid.Pers. brât(ar) "brother;" O.Pers. brata-; Av. brātar- "brother;" cognate with E. brother, as above.
A dusky color between red and black.
M.E. broun, from O.E. brun "dark," cf. Du. bruin, Ger. braun; PIE base *bher- "shining, brown," related to *bheros "dark animal" (cf. beaver, bear).
Qahvei-yi, color of qahvé "coffee."
Fr.: naine brune
A star-like object whose mass is too small to sustain → hydrogen fusion in its interior and become a star. Brown dwarfs are → substellar objects and occupy an intermediate regime between those of stars and giant planets. With a mass less than 0.08 times that of the Sun (about 80 → Jupiter masses), nuclear reactions in the core of brown dwarfs are limited to the transformation of → deuterium into 3He. The reason is that the cores of these objects are supported against → gravitational collapse by electron → degeneracy pressure (at early spectral types) and → Coulomb pressure (at later spectral types). Brown dwarfs, as ever cooling objects, will have late M dwarf spectral types within a few Myrs of their formation and gradually evolve as L, T and Y dwarfs → brown dwarf cooling. As late-M and early-L dwarfs, they overlap in temperature with the cool end of the stellar → main sequence (→ M dwarf, → L dwarf, → T dwarf, → Y dwarf). In contrast to the OBAFGKM sequence, the M-L-T-Y sequence is an evolutionary one. These objects were first postulated by Kumar (1963, ApJ 137, 1121 & 1126) and Hayashi & Nakano (1963, Prog. Theor.Phys. 30, 460).
brown dwarf cooling
sardeš-e kutule-ye qahve-yi
Fr.: refroidissement de naine brune
The process whereby a → brown dwarf cools over time after the → deuterium burning phase, which lasts a few 107 years. The → effective temperature and luminosity decrease depending on the mass, age, and → metallicity. Even though massive brown dwarfs may start out with star-like luminosity (≥ 10-3→ solar luminosities), they progressively fade with age to the point where, after 0.5 Gyr all → substellar objects are less luminous than the dimmest, lowest mass stars. More explicitly, brown dwarfs may start as star-like objects hotter than 2200 K, with → M dwarf spectral types, and, as they get older, pass through the later and cooler L, T, and Y spectral types (→ L dwarf, → T dwarf, → Y dwarf).
brown dwarf desert
kavir-e kutulehâ-ye qahvei
Fr.: désert des naines brunes
The observational result indicating a deficit in the frequency of → brown dwarf companions to Sun-like stars, either relative to the frequency of less massive planetary companions or relative to the frequency of more massive stellar companions. However, this desert exists mainly for low-separation brown dwarfs detected using orbital velocity surveys. No brown dwarf desert is noticed at wide separations (J. E. Gizis et al. 2001, ApJ 551, L163).
Fr.: mouvement brownien
The continuous random motion of solid microscopic particles immersed in a fluid due to bombardment by the atoms and molecules of the medium. The first quantitative explanation of the phenomenon, based on the kinetic theory of gases, was forwarded by A. Einstein in 1905.
Named after Robert Brown (1773-1858), a Scottish botanist, who first in 1827 noticed the erratic motion of pollen grains suspended in water. → motion.