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

A transition between two energy levels of an electron bound to a nucleus. The electron remains tied to the nucleus before and after the transition. → bound-free transition; → free-free emission.

Bound, p.p. of → bind; → transition.

A transition in which a bound electron is liberated. → free-bound emission; → free-free emission.

Bound, p.p. of → bind; → free.

1) Math: Restriction on the limits of applicability of an equation. In a differential equation, conditions that allow to fix the constant of integration and reach a unique solution. The number of boundary conditions necessary to determine a solution matches the order of the equation.
2) Physics: Conditions needed to determine the evolution of a system, given the physical laws.

→ boundary; → condition.

The function y = f(x) in a given range of the argument x if there exists a positive number M such that for all values of x in the range under consideration the inequality | f(x) | ≤ M will be fulfilled. → unbounded function.

→ bounded; → function.

A simplification in the equations of → hydrodynamics that treats the density as constant except in the → buoyancy term. This approximation is motivated by the fact that when pressure and temperature differences in a flow are small, then it follows from the thermodynamic → equation of state that a change in the density is also small.

Named after Joseph Valentin Boussinesq (1842-1929), a French physicist who made significant contributions to the theory of hydrodynamics, vibration, light, and heat; → approximation.

The formation of → breccia.

Verbal noun of → brecciate.

A statistical distribution of the brightness of an astronomical extended object.

→ brightness; → distribution.

Vâbâžeš, → distribution; deraxšandegi, → brightness.

A mathematical function appearing in the → magnetization equation of a → paramagnetic substance.

→ Brillouin zone; → zone.

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.

An international collaboration between Austria, Canada, and Poland, currently comprising five nano-satellites to investigate stellar structure and evolution of the brightest stars in the sky and their interaction with the local environment. BRITE is also used to study micropulsation, wind phenomena, and other forms of stellar variability. These nano-satellites aim to monitor stars brighter than V ~ 5 mag using two color pass-bands, over various observing campaigns. Each nano-satellite hosts a 3 cm telescope, providing a wide field of view (24° x 20°) to simultaneously observe up to a few dozen stars (Weiss et al. 2014).

BRITE, short for → BRIght Target Explorer; → bright; → target; → explorer.

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.

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.

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.

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.

Same as → 42 Orionis.

Star name in the → Bayer designation scheme.

The act, process, or result of calculating.

Calculation, noun from → calculate.

Afmâreš, verbal noun from afmârdan→ calculate.

The study of maximum and minimum properties of → definite integrals.

→ calculus; → variation.

Afmârik, → calculus; varteš→ variation.

One of the periods into which a calendar is divided, ordinarily 12, but in earlier systems 10 (the first Roman calendar under Romulus) or 13 (ancient Iranian calendar using a month intercalation).

→ calendar; → month.

1) The act or process of calibrating or the state of being calibrated.
2) A set of graduations that show positions or values.

Calibration, noun from → calibrate.

Kabizeš, noun from kabizidan, → calibrate.