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

A → substance that has a low → elastic limit. For example → glass, which breaks if its low elastic limit is exceeded.

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."

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; → band; → photometry.

A radio galaxy that shows broad optical emission lines. → broad-line region.

→ broad; → line; → radio galaxy.

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.

→ broad; → line; → region.

To make or become broad or broader.

→ borad.

Pahnidan, from pahn, → broad, + -idan infinitive suffix.

The act of making something wider. → instrumental broadening; → line broadening.

Broadening, from → broad + → -ing noun froming suffix.

Pahneš, from pahn (→ broad, present tense stem of pahnidan "to broaden" + -idan infinitive suffix) + eš verbal-noun suffix.

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.

A system of connected line → segments joined end to end.

Past participle of → break; → line.

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.

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.

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.

→ bronze; → age.

Son of the same parents as another person.

M.E.; O.E. brothor; cognate with Du. broeder, Ger. Bruder, Goth. brothar, Skt. bhrātr, Gk. phrater, L. frater, Pers. barâdar, as below, Rus. brat; PIE *bhrater.

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."

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).

The term brown dwarf was first used by Jill Tarter in her 1975 PhD thesis; → brown; → dwarf.

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; → cooling.

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).

→ brown; → dwarf; → desert.

The continuous random motion of solid microscopic particles immersed in a fluid, which is due to bombardment by the atoms and molecules of the medium. It is named after the botanist Robert Brown, who in 1827 first noticed that pollen seeds suspended in water moved in an irregular motion. While there were suspicions that the motion was caused by the collision of atoms against the particles, the first quantitative explanation of the phenomenon, based on the kinetic theory of gases, was forwarded by A. Einstein in 1905. When Einstein's paper appeared, the notion of atoms and molecules was still a subject of heated scientific debate. Ernst Mach and the physical chemist Wilhelm Ostwald were among those who chose to deny their existence.

Named after Robert Brown (1773-1858), a Scottish botanist, who first in 1827 noticed the erratic motion of pollen grains suspended in water. → motion.

The frequency at which an air parcel will oscillate when subjected to an infinitesimal perturbation in a stably stratified atmosphere. For a medium with a continuous density gradient, it is expressed by the formula: N² = -(g/ρ)∂ρ/∂z , where g is the → gravitational acceleration, ρ is density, and z geometric height. The stability condition is N > 0. It is also sometimes referred to as the buoyancy frequency. The higher the value of N the more stable the flow.

Named aster David Brunt (1886-1965), British meteorologist (1927, Q.J.R.Met.Soc. 53, 30) and Vilho Väisälä (1889-1969), Finnish meteorologist (1925, Soc. Sci. Fenn. Commental. Phys. Math. 2 (19), 19); → frequency.

General:A small body of gas within a liquid; a thin film of liquid inflated with air or gas.
Astro.: 1) Bubble-like structures of hot ionized gas created in the interstellar medium by the action of the powerful winds of massive stars.
2) A giant bubble-like component appearing during the growth of large-scale structures in the early Universe.

Bubble, from M.E. bobel, perhaps from M.Du. bobbel.

Tangol "bubble," from štiyâni dialect, maybe from tan "body" + gol "flower," literally "that which has a delicate body (like a flower)." This etymology is derived from the observation that in Pers. bubble is often likened to a flower: qonce-ye âb, kupale-ye âb, quze-ye âb [Dehxodâ] "water blossom, water flower, water bud."
Hobâb, from Ar. habâb.