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

A type of → interstellar dust grains with a size ranging from 150 to 1000 Å. Big grains consist of graphite and silicates. They are in → thermal equilibrium with the radiation field and their emission can be described by a modified → blackbody radiation following from → Kirchhoff's law.

→ big; → grain.

A cosmological hypothesis regarding the ultimate fate of the → Universe whereby in a far future galaxies and stellar systems would be torn apart due to the → accelerating expansion of the Universe depending on the kind of the → dark energy content of the Universe. According to this hypothesis, after the disruption of galaxies, stars, and planets even atoms might not be able to withstand the internal force of the expansion imposed by the dark energy.

→ big; M.E. rippen, origin obscure, cf. Frisian rippe "to tear, rip," M.Du. reppen, rippen "to pull, jerk," Swed. reppa, Dan. rippe "to tear, rip."

Meh "large, big," see under → big; gosast stem of gosastan "to tear, cut, break," from Mid.Pers. wisistan "to break, split," Av. saed-, sid- "to split, break," asista- "unsplit, unharmed," Skt. chid- "to split, break, cut off," PIE base *skei- "to cut, split," cf. Gk. skhizein "to split," L. scindere "to split," Goth. skaidan, O.E. sceadan "to divide, separate."

A → mapping  f from a → set  A onto a set B which is both an → injection and a → surjection. More explicitly, for every element b of B there is a unique element a of A for which f(a) = b. Also known as → bijective mapping.

From bi- + → injection.

Of or pertaining to a → bijection.

→ bi-; → injection.

Same as → bijection.

→ bijective; → mapping.

Same as → isomorphism.

→ bijective; → morphism.

Having or providing two modes, methods, systems, etc., in particular having or occurring with two statistical modes.

→ bi-; → modal.

A concept of → star formation in which → high-mass stars and → low-mass stars form in different physical conditions involving different → molecular clouds. Following the pioneering suggestion of Herbig (1962), successive investigations have generally supported the idea that star formation proceeds bimodally with respect to stellar mass. The star formation rate appears to differ both spatially and temporally for low mass and → massive stars. This is of considerable importance for galactic evolution, since the low-mass stars lock up mass and are long-lived, low luminosity survivors to the present epoch, whereas massive stars are short-lived, recycle and enrich interstellar gas, and leave dark remnants while producing a high luminosity per unit of mass (Silk, J., 1988, in Galactic and Extragalactic Star Formation, p. 503, eds. R. E. Pudritz and M. Fich).

→ bimodal; → star; → formation.

The quality or state of being → bimodal.

→ bimodal; → -ity.

1a) General:A box or enclosed space for storing grain, coal, or the like.
1b) Electronics: In a → CCD detector, a square or rectangular group of adjacent → pixels used collectively to transport the → electron charges.
1c) In a statistical → histogram, the range of → distribution → intervals. The bin widths (or the number of bins) affect a histogram.
2) To place in a → bin; to create → binning.

M.E. binne, O.E. binn(e) "manger, crib," perhaps from O.Celt. *benna, akin to Welsh benn "a cart, especially one with a woven wicker body." The same Celtic word seems to be preserved in It. benna "dung cart," Fr. benne "a sort of box for transporting materials, especially in mines," Du. benne "large basket," from L.L. benna.

Bâvin "a basket, more precisely a small basket which contains the cotton to be spun;" bâvinidan infinitive from bâvin.

The quality or condition of being binary.

→ binary; → -ity.

General: Characterized by or consisting of two parts or components.
Math.: Of or relating to a system of numeration having 2 as its base.
Astro.: Physically associated pair of astronomical objects.

Binary, from L.L. binarius, from bini "two-by-two," from bis "twice, two times;" cf. Av. biš- "twice," bi- "two," Mod.Pers. do "two," PIE *dwo- "two."

Dorin, from Mid.Pers. dorin "double, pair," from do (Av. dva-, Skt. dvi-, Gk. duo, L. duo, E. two, Der. zwei, Fr. deux) "two" + rin "time, turn."
Dodoyi "two-by-two," from do, → two.

A system of calculation in which the only numerals used are 0 and 1. All the real numbers are represented in terms of powers of 2.

→ binary; → arithmetic.

A member of a population of double objects in the main → Asteroid Belt or the → Kuiper Belt which are gravitationally bound together. So far about 200 such binary systems have been identified, while their number is increasing. 243 Ida was the first binary asteroid to be discovered during the Galileo spacecraft flyby in 1993. Other examples are → Antiope and Kalliope in the main belt and QG₂₉₈ in the Kuiper Belt. The importance of these objects resides in the fact that systems with well measured orbital parameters allow the total mass to be estimated. If the sizes of the components are known then their densities can be accurately calculated. Density is an important parameter since it yields information about composition and internal structure.

→ binary; → asteroid.

A → binary system consisting of two → black holes in close orbit around each other. Same as → black hole binary.

→ binary; → black; → hole.

Either of the digits 0 or 1, used in the → binary number system.

→ binary, → digit.

The fraction of stars that have at least one → companion. It is at least 50%. The binary fraction appears to increase with increasing → primary star mass, at least among the more massive stars: the → O stars and → B stars have a companion frequency of at least 70%, while for the → G stars the binary frequency is around 50% and the → M stars may have an even lower binary frequency of around 30-40%. Brown dwarfs are rare as companions to lower-main-sequence stars, although brown-dwarf binaries appear not to be rare. An increase in binary frequency with mass would be expected if most stars form in → multiple systems that disintegrate, since the more massive stars would then preferentially remain in binaries while the less massive ones would preferentially be ejected as single stars (see Richard B. Larson, 2001, in IAU Symposium 200, p. 93 and references therein).

→ binary; → frequency.

A pair of galaxies in orbit around each other.

→ binary; → galaxy.

Kahkašân, → galaxy; dorin→ binary.

A → numeral system that has 2 as its base and uses only two digits, 0 and 1. The positional value of each digit in a binary number is twice the place value of the digit of its right side. Each binary digit is known as a bit. The decimal numbers from 0 to 10 are thus in binary 0, 1, 10, 11, 100, 101, 110, 111, 1000, 1001, and 1010. And, for example, the binary number 11101₂ represents the decimal number (1 × 2⁴) + (1 × 2³) + (1 × 2²) + (0 × 2¹) + (1 × 2⁰), or 29. In electronics, binary numbers are the flow of information in the form of zeros and ones used by computers. Computers use it to manipulate and store all of their data including numbers, words, videos, graphics, and music.

→ binary; → number; → system.

A mathematical operation that combines two numbers, quantities, sets, etc., to give a third. For example, multiplication of two numbers is a binary operation.
A binary operation * on a set S is → commutative if a * b = b * a for all a, b∈ S.
A binary operation * on a set S is → associative if (a * b) * c = a * (b * c) for all a, b, c∈ S.

→ binary; → operation.