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

The process in which an atomic, nuclear, or astronomical system acquires an additional particle or body.

From M.Fr. capture "a taking," from L. captura "a taking," from captus p.p. of capere "to take, hold, seize;" PIE base *kap- "to grasp" (cf. Skt. kapati "measure equal to the capacity of the hollows of the two hands joined;" Gk. kaptein "to swallow;" O.Ir. cacht "servant-girl," literally "captive;" Goth. haban "have, hold;" O.E. habban, E. have "to have, hold;" probably Mod.Pers. qâp-, qâpidan, kapidan "to seize, rob").

Gir-oft, composite verb from gir + oft. Gir "take, seize, hold," from gereftan, from O.Pers./Av. grab- "to take, seize," cf. Skt. grah-, grabh- "to seize, take," graha- "seizing, holding, perceiving," M.L.G. grabben "to grab," from P.Gmc. *grab, E. grab "to take or grasp suddenly;" PIE *ghrebh- "to seize." Oft, from oftâtan "to fall; to befal, happen," Mid.Pers. opastan, Av. pat- " to fly, fall, rush," Skt. patati "he flies, falls," L. petere "to fall, rush out," Gk. piptein "to fall," PIE base *pet- "to fly, to rush." Gir-andâzi, from gir + andâzi, verbal noun from gir-andâxtan "to throw, cast; to do, make."

One of the first scientific hypotheses about the formation of the Moon, according to which the Moon formed elsewhere in the solar system and was pulled into a stable orbit by Earth's gravity. Observational facts do not confirm this hypothesis. For example, analysis of rocks from the Apollo landings confirm the Moon is made of similar material and rock as the Earth from about the same time and have almost identical oxygen isotopes in them. Moreover, a captured moon, like Mars' → Phobos and → Deimos do not have a spherical shape. See also → giant impact hypothesis, → fission theory, → co-formation theory.

→ capture; → theory.

A process whereby an → unstable atom becomes stable. In this process, an → electron in an atom's inner shell is drawn into the → nucleus where it combines with a → proton, forming a → neutron and a → neutrino. The neutrino escapes from the atom's nucleus. The result is an element change, because the atom loses a proton. For example, an atom of → carbon (with 6 protons) becomes an atom of → boron (with 5 protons). Electron capture is also called K-capture since the captured electron usually comes from the atom's K-shell. See also → neutronization.

→ electron; → capture.

The → nuclear reaction that occurs when an → atomic nucleus captures a → neutron. Neutron capture is the primary mechanism (principally, the → s-process and → r-process) by which very massive nuclei are formed in stars and during → supernova explosions. Instead of → fusion of similar nuclei, heavy, → neutron-capture elements are created by the addition of more and more neutrons to existing nuclei.

→ neutron; → capture.

A → nucleosynthesis process responsible for the generation of the → chemical elements heavier than the → iron peak elements. There are two possibilities for → neutron capture: the slow neutron-capture process (the → s-process) and the rapid neutron-capture process (the → r-process). The s-process is further divided into two categories: the weak s-component and the main s-component. Massive stars are sites of the weak component of s-process nucleosynthesis, which is mainly responsible for the production of lighter neutron-capture elements (e.g. Sr, Y, and Zr). The s-process contribution to heavier neutron-capture elements (heavier than Ba) is due only to the main s-component. The low- to intermediate-mass stars (about 1.3-8 Msun) in the → asymptotic giant branch (AGB) are usually considered to be sites in which the main s-process occur. There is abundant evidence suggesting that → Type II supernova (SNe II) are sites for the synthesis of the r-process nuclei, although this has not yet been fully confirmed. The observations and analysis on → very metal-poor stars imply that the stars with [Fe/H] ≤ -2.5 might form from gas clouds polluted by a few supernovae (SNe). Therefore, the abundances of → heavy elements in → metal-poor stars have been used to learn about the nature of the nucleosynthetic processes in the early Galaxy (See, e.g., H. Li et al., 2013, arXiv:1301.6097).

→ neutron;→ capture; → element.

Capture of a free electron by an ion with the subsequent emission of photons; also called → radiative recombination.

→ radiative; → capture.

Capture by an atomic nucleus of a particle whose energy is equal to one of the energy levels of the nucleus.

→ resonance; → capture.

A process in which two stars remain → bound after their → close encounter, leading to the formation of a → binary system. Tidal capture becomes possible when two stars pass each other so closely (within a few stellar radii) that their → tidal forces are able to absorb the excess energy of → unbound → orbital motion. The process was originally suggested by Fabian et al. (1975) to explain the origin of → low-mass X-ray binary systems observed for the first time in → globular clusters.

→ tidal; → capture.