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

1) A branching or division into two parts; a splitting apart.
2) A sudden qualitative change in the behavior of a → dynamical system. The equation describing the evolution of the system finds several solutions for certain values of a parameter. Systems undergoing a bifurcation do not necessarily return to their original state, even if the parameter returns to its nominal value. See also → chaos.

Verbal noun of → bifurcate.

The point or moment in the evolution of a → dynamical system that occurs if a parameter passes through a critical point. At this point the system branches into any number of qualitatively new types of behavior.

→ bifurcation; → point.

1) A theory which studies how, in certain nonlinear systems, there may be paths and shifts in behavior dependent on small changes in circumstances or the current position of the system.
2) Math.: The study of the behavior of a solution of a nonlinear problem in the neighborhood of a known solution, particularly as a parameter varies.

→ bifurcation; → theory.

An expression of the form x^m(a + bxⁿ)^pdx, where m, n, p, a, and b are constants.

→ binomial; → differential.

The apparent shift of the wavelength towards the shorter wavelength region of the radiation spectrum of an approaching object due to the Doppler effect.

→ blue; → shift.

A constituent of a composite astronomical object which has a motion directed towards the observer, as revealed by its spectrum.

→ blueshift; → component.

A system for the classification of → S-type stars. The system involves the designations of a C/O index and a temperature type. Moreover, when possible, it uses intensity estimates for → ZrO bands, the → TiO bands, the → Na I D-lines, the YO bands, and the Li I 6708 line.

Philip C. Keenan & Patricia C. Boeshaar, 1980, ApJS, 43, 379; → classification.

A → claculus based on the properties of the successive values of → variable quantities and their → differences or → increments.

→ calculus, → finite, → difference.

Afmârik, → calculus, degarsânihâ, plural of degarsân, → difference, karânmand, → finite.

Same as → central peak.

→ central; → up; → lift.

→ central; → uplift.

Acting or moving in a direction away from the axis of rotation or the center of a circle along which a body is moving.

From Mod.L., coined 1687 by Sir Isaac Newton from L. centri-, combining form of centrum, → center, + fugere "to run away, flee."

Markaz-goriz, from markaz, → center, + goriz "running away," from gorixtan, gorizidan "to run away," Mid.Pers. virextan, proto-Iranian *vi-raik, from vi- "apart, asunder" + *raik, Av. raek- "to leave, set free, let off," Mid./Mod.Pers. reg/rig (in mordé-rig "inheritance," Skt. ric- "to leave," rinakti "gives up, evacuates," Gk. leipein "to leave," L. linquere "to leave," from PIE *linkw-, from *leikw- "to leave behind" (cf. Goth. leihvan, O.E. lænan "to lend;" O.H.G. lihan "to borrow;" O.N. lan "loan").

Of a point rotating in a circle round a central point, the outward acceleration away from the rotation axis. It corresponds to → centrifugal force. The centrifugal acceleration is given by ω x ω x r, or v²/r, where ω is → angular velocity, r the distance to the rotating axis, and v the → tangential velocity. The centrifugal and → centripetal accelerations are equal and opposite.

→ centrifugal; → acceleration.

A force in a rotating reference frame directed outward from the axis of rotation.

→ centrifugal; → force.

The action of making a statement or situation less confused and more comprehensible.

Verbal noun of → clarify.

1) To make (an idea, statement, etc.) clear or intelligible; to free from ambiguity.
2) To remove solid matter from (a liquid); to make into a clear or pellucid liquid (Dictionary.com).

→ clear; → -fy.

The systematic grouping of astronomical objects into categories on the basis of physical, morphological, or evolutionary characteristics.

Classification, from O.Fr., from classifier, from → class + -fier, from L. -ficare, root of facere "to make, do;" PIE base *dhe- "to put, to do" (cf. Skt. dadhati "puts, places;" Av. dadaiti "he puts," O.Pers. ada "he made," Gk. tithenai "to put, set, place."

Radebandi, from radé, → class, + bandi, verbal noun of bastan "to bind, shut; to get, acquire, incur," from Mid.Pers. bastan/vastan "to bind, shut;" Av./O.Pers. band- "to bind, fetter," banda- "band, tie;" cf. Skt. bandh- "to bind, tie, fasten;" Ger. binden, E. bind, → band; PIE base *bhendh- "to bind."

A very high steep rock or ice face, especially one that runs along a coastline. → scarp.

M.E., O.E. clif (cf. O.S. clif, O.N. klif, O.H.G. klep, M.Du. klippe, Ger. Klippe "cliff, steep rock").

Tondân, from tond "swift, rapid, brisk," → scarp + -ân a suffix of nuance/relation.

1) Math.: A process applied to topological spaces having many dimensions to make them compact spaces.
2) Physics: In string theory, the process of "curling up" the extra dimensions (six in the superstring theory). According to these theories, the Universe actually has 10 spatial dimensions but that 7 of them have become "compactified" down to subatomic size and thus are unobservable.

Compactification, n. from → compactify.

Verbal form of → compactification.

Compactify, from → compact + -ify "cause to become," M.E. -fien, from O.Fr. -fier, from L. -ficare, root of facere "to make, do;" PIE base *dhe- "to put, to do" (cf. Skt. dadhati "puts, places;" Av. dadaiti "he puts," O.Pers. ada "he made," Gk. tithenai "to put, set, place."

Of the → Compton effect, the amount of increase in the wavelength of an energetic photon upon its collision with an electron.

→ Compton; → shift.

A mapping of an infinite → space-time onto a finite one that may make the far away parts of the former accessible to study. The technique invented by Penrose defines an equivalence class of → metrics, g_ab being equivalent to ĝ_ab = Ω²g_ab, where Ω is a positive scalar function of the space-time that modifies the distance scale making the asymptotics of the physical metric accessible to study.

→ conformal; → compactification.