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

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.

A tank filled with a transparent liquid that is on the brink of boiling. When a charged particle passes through the liquid, the energy deposited initiates boiling along the path, leaving a trail of tiny bubbles. The bubble chamber is no longer in wide use for particle experiments.

→ bubble; → chamber.

The → diffuse nebula NGC 7635 in the constellation → Cassiopeia lying at a distance of about 11,000 light-years. About 10 light-years across, it is visible with a small telescope.

→ bubble; → nebula.

A defect or imperfection, as in a mechanical device, computer program, or plan (Dictionary.com).

From bugge "beetle," apparently alteration of M.E. budde, O.E. -budda "beetle."

Bug, from Kurd. Kurmanji bihuk "bug, insect."

The double-lobed → planetary nebula NGC 6302, which lies in → Scorpius at a distance of about 4000 → light-years. The central very hot star seems to have violently ejected material in two distinct directions.

→ bug; → nebula.

Šâparak "night butterfly, bat," from šab "night" + parak "flying," from paridan "to fly."

1) A rounded projection, bend, or protruding part; protuberance; hump (Dictionary.com).
2) → galaxy bulge.

Bulge, from O.Fr. bouge "leather bag," from L. bulga "leather bag," of Gaulish origin.

Kuži "convexity," from kuž, → convex.
Barâmadegi, from barâmadan "to grow out; to emerge," from bar- "on, upon, up" (Mid.Pers. abar, O.Pers. upariy "above; over, upon, according to," Av. upairi "above, over," upairi.zəma- "located above the earth;" cf. Gk. hyper- "over, above;" L. super-; O.H.G. ubir "over;" PIE base *uper "over") + âmadan "to come" (Mid.Pers. âmadan; O.Pers. gam- "to come; to go;" Av. gam- "to come; to go," jamaiti "goes;" cf. Skt. gamati "goes;" Gk. bainein "to go, walk, step;" L. venire "to come;" Tocharian A käm- "to come;" O.H.G. queman "to come;" E. come; PIE root *gwem- "to go, come").

1) A small, metal object that is fired from a gun.
2) Something resembling a bullet, in shape or effect. → Bullet cluster.

From M.Fr. boulette "cannonball, small ball," diminutive of boule "a ball," from L. bulla "round thing, bubble, knob," cognate with bowl and boil.

Golulé "bullet," variants gullé, goruk, gulu, gudé, guy "ball, sphere;" cf. Skt. guda- "ball, mouthful, lump, tumour;" Pali gula- "ball;" Gk. gloutos "rump;" L. glomus "ball," globus "globe;" Ger. Kugel, E. clot; PIE *gel- "to make into a ball."

A → cluster of galaxies at a → redshift of z = 0.296 undergoing a violent → merger process nearly in the → plane of the sky. Also known as 1E 0657-558. The head-on collision between the main cluster and a subcluster ramming with an apparent speed of about 4700 km s^-1 occurred about 150 x 10⁶ years ago. The two clusters are currently moving away from each other while the space between them is filled with a very hot gas (first observed in X-rays by → Chandra) resulting from the overheating due to the collision. The Bullet cluster has the highest X-ray luminosity and temperature of all known clusters. The X-ray gas of the bullet (amounting to 2 x 10¹³ solar masses) collides with the X-ray gas of the main cluster (10¹⁴ solar masses) and forms a well defined → supersonic (Mach 3) → bow shock. A significant offset between the distribution of X-ray emission and the mass distribution has been observed, and diversely interpreted.

The name Bullet refers to the smaller subcluster, that has created the bow shock; → cluster.

A subtype of classical → Cepheid variable stars that show a bump on the descending branch of their → light curve.

Bump "a relatively abrupt convexity or bulge on a surface," probably imitative of the sound of a blow; → Cepheid.

Quzdâr, from quz "hump," variant of kuž, → convex, + -dâr "possessing," from dâštan "to have, possess." Zokdâr, from Lori zok "a raised spot, a bulge," cf. Northern Fârs Âbâdé dialect lok " swellimg, knob;" Kefeusi, → Cepheid.

The upward force that a → fluid exerts on an immersed body which is less dense than the fluid. It is equal to the → weight of the fluid displaced. Thus a body weighs less when weighed in water, the apparent loss in weight being equal to the weight of the water displaced. Buoyancy allows a boat to float on water and provides lift for balloons. See also → buoyant force; → Archimedes' principle.

From buoy, → buoyant + -ancy a suffix used to form nouns denoting state or quality, from L. -antia, from -ant + -ia.

Bâlârâni literally "pushing up," from bâlâ "up, above, high, elevated, height" (variants boland "high, tall, elevated, sublime," borz "height, magnitude" (it occurs also in the name of the mountain chain Alborz), Laki dialect berg "hill, mountain;" Mid.Pers. buland "high;" O.Pers. baršan- "height;" Av. barəz- "high, mount," barezan- "height;" cf. Skt. bhrant- "high;" L. fortis "strong" (Fr. and E. force); O.E. burg, burh "castle, fortified place," from P.Gmc. *burgs "fortress;" Ger. Burg "castle," Goth. baurgs "city," E. burg, borough, Fr. bourgeois, bourgeoisie, faubourg; PIE base *bhergh- "high") + râni verbal noun of rândan "to push, drive, cause to go," causative of raftan "to go, walk, proceed" (present tense stem row-, Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack").

Same as the → Brunt-Vaisala frequency.

→ buoyancy; → frequency.

The force that causes immersed bodies to float or rise to the surface of a liquid or upward in a gas. Buoyant force is produced by → gravity and density differences. Same as → buoyancy.

From buoy (current meaning) "a float moored in water to mark a location," from M.E. boye, from O.Fr. buie or M.Du. boeye, from L. boia "fetter, chain" + suffix -ant; → force.

1) (v.intr.) To undergo combustion (fast or slow).
To undergo fusion or fission.
2) (v.tr.) To cause to undergo combustion.
To use as fuel or as a source of heat.

Burn, from M.E. bernen, brennen, combination of O.E. beornan (intr.) and bærnan (tr.), both from P.Gmc. *brenwanan; cf. Goth. brannjan, O.H.G. brennen.

Suxtan, suzândan, from Mid.Pers. sôxtan, sôzidan "to burn;" Av. base saoc- "to burn, inflame" sūcā "brilliance," upa.suxta- "inflamed;" cf. Skt. śoc- "to light, glow, burn," śocati "burns," (caus.) socayati, śuc- "flame, glow," śoka- "light, flame;" PIE base *(s)keuk- "to shine."

The state, process, or effect of being on fire, burned, or subjected to intense heat. → helium burning; → neon burning; → oxygen burning; → shell burning.

Verbal noun of → burn.

A piece of glass of roundish shape, possibly made of rock crystals or a globular container filled with water, whose use is attested in ancient civilizations. In his comedy The Clouds, the Greek playwright Aristophanes (448-380 BC) mentions globules of glass that were known as burning spheres. Several Roman writers (Pliny, Seneca, Plutarch) speak of burning glasses. In particular, Seneca specifies that small and indistinct written characters appear larger and clearer when viewed through a globular glass filled with water. See also → magnifying glass.

→ burning; → sphere.

Guy, → globe; suzân "burning," → burning.

1a) General: An abrupt, intense increase. A period of intense activity. A sudden outbreak or outburst. An explosion.
1b) Astro.: A period of abrupt increase in the intensity of a phenomenon, for example → star formation rate or emission of radiation such as → X-ray burst, → gamma-ray burst, or → cosmic-ray burst. See also → burst of star formation, → starburst galaxy.
2) To come open or fly apart suddenly or violently, especially from internal pressure.

M.E. bersten, from O.E. berstan, akin to O.H.G. berstan "to burst;" from PIE *bhres- "to burst, break, crack."

1) Belk, Mod.Pers. "a blaze, a flame." The term has several variants, including in dialects: balk [Mo'in], pâlk (Tokharian AB), bal (Gilaki, Semnâni, Sorxeyi, Sangesari, Lahijâni), val (Gilaki), bilese (Kordi), beleyz (Lori), warq, barx [Mo'in], and the Pers. widespread term gorr "burst of fire." Belk derives probably from Mid.Pers. brâh, Av. braz- "to shine, gleam, flash, radiate," cf. Skt. bhâ- "to shine," bhrajate "shines, glitters," O.H.G. beraht "bright," O.E. beorht "bright;" PIE *bhereg- "to shine." The Mod.Pers. barq "glitter; → electricity" probably belongs to this family. Therefore, the Hebrew barak and Ar. barq may be loanwords from Old or Mid.Pers.
2) Belkidan, from belk + infinitive suffix -idan.

An intense → star formation activity in a region of → interstellar medium or, more globally, in a → galaxy. It is characterized by a → star formation rate which is much higher than the corresponding average. Same as → starburst.

→ burst; → star; → formation.