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

A binary star in which the presence of an unresolved companion is revealed by small oscillations in the movement of the visible component caused by the gravitational influence of the unseen component.

→ astrometry; → binary.

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.

A pulsar in a → binary system, the companion of which often being a → neutron star or a → white dwarf. The only known binary system with two pulsars components is the → double pulsar. As of 2010 about 70 binary pulsars have been identified. They are ideal laboratories for testing and studying the effects predicted by → general relativity, such as → spin precession, → Shapiro time delay, and → gravitational waves. The prototype, called PSR 1913+16, was discovered in 1974 by Russell A. Hulse and Joseph H. Taylor, Jr., who received the Nobel Prize for Physics in 1993. → Hulse-Taylor pulsar.

→ binary; → pulsar.

Two stars gravitationally bound to each other, so that they revolve around their common center of gravity. → double star; → spectroscopic binary.

→ binary; → star.

Setâré, → star; dorin, → binary.

A → dual supermassive black hole whose components are separated by a few parsecs.

→ binary; → supermassive; → black; → hole.

Two astronomical objects revolving around their common center of mass.

→ binary; → system.

Râžmân, → system; dorin→ binary.

In → graph theory, an → ordered tree with all → nodes having at most two → children.

→ binary; → tree.

In star formation models, the population of binary components formed via random pairing of stars distributed according to the → canonical IMF.

→ birth; → binary; → population.

A → binary system in which each component is a → black hole. The binary's evolution can be divided into three stages: → inspiral, → merger, and → ringdown.

→ black; → hole; → binary.

Of or relating to an object that revolves around a → binary system.

→ circum- + → binary.

A relatively thin structure of matter composed mainly of gas and dust that orbits both the → primary and → secondary stars in → binary systems.

→ circumbinary; → disk.

A binary system in which the separation of the component stars is comparable to their diameters, so that they influence each other's evolution most commonly by the tidal forces.

→ close; → binary; → star.