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

A → pair of → vectors whose directions are parallel but having the opposite sense.

→ anti-; → parallel.

Any → elementary particle with a → charge of opposite sign to the same particle in normal matter.

→ anti- "opposite, opposing, against" + → particle.

1) Of or relating to the → antipodes.
2) Describing two points when a line drawn from one to the other does not pass through the geometric centre of the Earth.

→ antipode; → -al.

1) The exact or direct opposite.
2) Either or both of two points, places, or regions that are situated diametrically opposite to one another on the Earth's surface (Dictionary.com).

M.E., from L., from Gk. antipod-, antipous, literally "with feet opposite," from → anti- "against," + pod-, pous, → foot.

Pâdpây, from pâd-, → anti-, + pây, → foot.

The antiparticle of a proton, identical in mass and spin but of opposite (negative) charge.

From → anti- + → proton.

An electric → charge distribution consisting of more than four → positive and → negative → electric charges located at a small distance from each other. The multipole concept is an extension of the → electric quadrupole. For the generalized multipole characterized by the letter l, the potential at a distance r varies as 1/r^{l + 1} and the field intensity as 1/r^{l + 2}.

→ electric; → multipole.

One of the three quantities (k, α, and δ) which are used in the → radiation-driven wind theory to express the radiation pressure due to spectral lines. These coefficients parametrize the radiation acceleration as: g_rad≅ k(dv/dr)^αg_e, where g_e = σ_eL/4πcR_*² is the radiative acceleration by electron scattering. The parameter k is dependent on the number of lines that produce the radiation pressure. The parameter α depends on the optical depth of the driving lines and varies between 0 (optically thin) and 1 (optically thick). The parameter δ describes the dependence of k on the density with k ≅ ρ^δ. The velocity law of radiation-driven winds depends on α and δ, but not on k. The → mass loss rate depends on k, α, and δ (Castor et al. 1975, ApJ 195, 157; Lamers et al., 1995, ApJ 455, 269 and references therein).

→ force; → multiplier; → parameter.

A → multiple star system in which the stars can be divided into two groups, each of which traverses a larger orbit around the system's center of mass. Each of these smaller groups must also be hierarchical, which means that they must be divided into smaller subgroups which themselves are hierarchical, and so on. Hierarchical multiple systems have long-term dynamical stability.

→ hierarchical; → multiple; → system.

Math.: A constant that appears in the process for obtaining extrema of functions of several variables. Suppose that the function f(x,y) has to be maximized by choice of x and y subject to the constraint that g(x,y)≤ k. The solution can be found by constructing the → Lagrangian function  L(x,y,λ) = f(x,y) + λ[k - g(x,y)], where λ is the Lagrangian multiplier.

→ Lagrangian point; → multiplier.

Of two or more → integers, the smallest positive number that is divisible by those integers without a remainder.

→ least; → common; → multiplier.

A stellar system with more than one orbiting planet.

→ multi-; → planet; → system.

Consisting of, having, or involving several or many individuals, parts, elements, etc.
Math.: A number that contains another number an integral number of times without a remainder: 25 is a multiple of 5.

From Fr. multiple, from L.L. multiplus "manifold," from L. → multi- "many, much" + -plus "fold," from base of plicare "to fold, twist."

Bastâ-, from bas "many, much" (Mid.Pers. vas "many, much;" O.Pers. vasiy "at will, greatly, utterly;" Av. varəmi "I wish," vasô, vasə "at one's pleasure or will," from vas- "to will, desire, wish") + tâ "fold, plait, ply; piece, part," also a multiplicative suffix; Mid.Pers. tâg "piece, part."

The division of a relatively long exposure into several successive shorter ones, e.g. to avoid detector saturation.

→ multiple; → exposure.

A series of successive integrations in which the integral operator acts on the result of preceding integration.

→ multiple; → integral.

A process of → radiative transfer in which more than one → scattering event may be of importance before → transmission, → reflection, or → absorption. In → radiation-driven winds photon scattering can take place in different → spectral lines. Each scattering occurs in a different spectral line, and successive scatterings occur at lower energies (longer wavelength). The standard theory of line driving (→ CAK model) assumes that photons can be scattered only once in the wind, which is a reasonable assumption for normal → O stars. In → Wolf-Rayet stars, where photons evolve in an atmosphere with a strong → ionization stratification, multiple scattering is important. Indeed the strength of W-R winds appears to exceed the single scattering limit.

→ multiple; → scattering.

A star which appears single but is in fact composed of more than two components. See also → multiple star system; → binary star; → triple star.

→ multiple; → star.

A stellar system composed of several stars bound together by gravitational attraction and revolving around a common center of mass.

→ multiple; → star; → system.

1) A system consisting of several → components.
2) → multiple star system.

→ multiple; → system.

A group of spectral lines arising from transitions having a common lower energy level.

From → multi- + -plet on the model of triplet.

Bastâyé, from bastâ-→ multi- + euphonic -yé, from -é nuance suffix.

A number to be multiplied by another.

From L. multiplicandum, from multiplicandus "to be multiplied," gerundive of multiplicare, → multiply.

Bastâšow, literally "that undergoes multiplication," from bastâ, → multiple, + šow, present stem and agent noun of šodan "to become, to be, to be doing, to go, to pass," from Mid.Pers. šudan, šaw- "to go;" Av. šiyav-, š(ii)auu- "to move, go," šiyavati "goes," šyaoθna- "activity; action; doing, working;" O.Pers. šiyav- "to go forth, set," ašiyavam "I set forth;" cf. Skt. cyu- "to move to and fro, shake about; to stir," cyávate "stirs himself, goes;" Gk. kinein "to move;" Goth. haitan "call, be called;" O.E. hatan "command, call;" PIE base *kei- "to move to and fro."