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

Having little or no space between elements or parts, as in → close binary, → close approach; tight and compact.

M.E. clos, closed, from O.Fr., from L. clausus, p.p. of claudere "to close."

Kip "close, tight" in spoken Pers.

In astronomy a general term to describe the positions of two or more objects that come unusually near one to another. In particular, regarding an asteroid's position with respect to Earth, when it is within the Moon's orbit.

→ close; → approach.

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.

A → binary system in which the distance separating the stars is comparable to their size. Most close binaries are spectroscopic binaries (→ spectroscopic binary) and/or eclipsing binaries (→ eclipsing binary). In most of them → mass transfer occurs at some stage, an event which profoundly affects the → stellar evolution of the components. The evolution of close binaries depends on the → initial masses of the two stars and their → separation. When the more massive star evolves into a → red giant first, material will spill through the inner point onto its companion, thereby affecting its companion's evolution. Mass transfer can also alter the separation and → orbital period of the binary star.

→ close; → binary; → system.

1) In a → star cluster, coming across of two stars so closely that their → orbits alter by their mutual → gravitational attractions.
2) As regards an → asteroid or → comet, a situation when it crosses the Moon's orbit and approaches the Earth with a risk of collision. See also → close approach, → encounter.

→ close; → encounter.

Having boundaries; limited. → closed curve; → closed Universe.

Closed, p.p. of close, from M.E. clos, from O.Fr., from clore "to shut," from L. clausus, p.p. of claudere "to close."

Basté p.p.of bastan, from Mid.Pers. bastan/vastan "to bind, shut," Av./O.Pers. band- "to bind, fetter," banda- "band, tie," Skt. bandh- "to bind, tie, fasten," PIE *bhendh- "to bind," cf. Ger. binden, E. bind, → band.

A curve whose ends are joined.

→ closed; → curve.

A bounded space the surface of which has the property that if one travels in any direction upon it without changing direction, one will end up back to the departure point. An example is a sphere. Triangles which lie on the surface of a closed space will have a sum of angles which is greater than 180°. An closed space has a positive → curvature. See also → closed Universe, → open space.

→ closed; → space.

Thermodynamics: A system which can exchange energy with the surroundings but not matter. → open system; → isolated system.

→ closed; → system.

A → cosmological model, first formulated by Friedmann and Lemaître, in which the Universe has a → finite size and lifetime and → space has a → positive → curvature, e.g. a Universe with a density greater than the → critical density. See also → closed space.

→ closed; → Universe.

In → predicate logic, a → wff with no → free occurrences of any → variable. Also called a → sentence.

→ closed; → wff.

A → close binary system composed of two → massive stars.

→ massive; → close binary star.

A subsystem if its intrinsic energy is large, on the average, with respect to the energy of its interaction with other portions of the → closed system.

→ quasi-; → closed; → subsystem.