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

The apparent path described by a star on the → celestial sphere due → annual aberration. A star at the → ecliptic pole is seen to move around a circle of angular radius about 20".50, once a year. A star on the → ecliptic oscillates to and fro along a line of angular half-length 20".50. At an intermediate → celestial latitude, β, the aberration orbit is an ellipse, with semi-major axis 20".50 and semi-minor axis (20".50) sin β.

→ aberration; → orbit.

1) Based on individual will or choice rather than by reason or necessity.
2) Math.: Undetermined; of unspecified value. → arbitrary constant.

M.E., from O.Fr. arbitraire or directly from L. arbitrarius "depending on the will, uncertain," from → ad- "to" + baetere "to come, go."

Kâmsar, literally "at one's will," from kâm "desire, wish; cause, reason," → despite, + sar "person, individual," originally "→ head."

A constant quantity in → equations which takes various values but which remains unaffected by the changes in the values of the → variables of the equation. Most → differential equations have more than one → solution. In general, the number of arbitrary constants of an ordinary differential equation is given by the → order of the highest → derivative.

→ arbitrary; → constant.

Either of the digits 0 or 1, used in the → binary number system.

→ binary, → digit.

A contraction of → binary digit, either 0 or 1.

Bit, from binary + digit

The orbit described by an object around a central gravitational force in a system whose total energy is negative. An elliptical orbit.

Bound, p.p. of → bind; → orbit.

Madâr, → orbit; bandidé, p.p. of bandidan, → bind.

The path of a object in → circular motion.

→ circular; → orbit.

A zone around a star within which a planet can have temperatures that permit liquid water, depending on the luminosity of the star and the distance of the planet from it.

→ circumstellar; → habitable zone.

Of or relating to two or more celestial bodies that share, or almost share, the same orbit.

→ co-; → orbital.

The motion of two or more bodies around the Sun on different orbits when it takes them the same amount of time to complete one revolution. There are three possible types of co-orbital motions of a small body associated with a planet: → tadpole orbits, → horseshoe orbits, and → quasi-satellite orbits.

→ co-orbital; → motion.

Any of satellites which either share the same orbit or which occupy immediately adjacent orbits that change periodically as the satellites approach one another (Ellis et al., 2007, Planetary Ring Systems, Springer).

→ co-orbital; → satellite.

The action or quality of a → co-orbiting asteroid.

From co- "together," → com- + → orbit + → -ing.

From ham- "together," → com- + madâr→ orbit + -i noun suffix.

An asteroid having a → co-orbital motion.

→ co-orbiting; → asteroid.

The → path followed by a → comet in the → solar system around the → Sun. Most cometary orbits appear to be → elliptical, or in some cases → parabolic. The orbits of → short-period comets are elliptical, carrying them out to a region lying from → Jupiter to beyond the orbit of → Neptune. Those of → long-period comets are very elliptical. The orbits may be strongly influenced if they pass near the Jovian planets, particularly Jupiter itself. The cometary orbits are also influenced to some degree by gases shooting out of comets, so their orbits are primarily but not completely determined by gravity. Newton (1644-1727) was the first to compute a cometary orbit. He found that the comet of 1680 was following a parabolic orbit around the Sun. Edmond Halley (1656-1742), following the methods of Newton, computed the → orbital elements of 24 comets. He realized that the comets of 1531, 1607 and 1682 had very similar elements and postulated that they were in fact the same object, orbiting an elongated ellipse. He predicted the next return to occur in 1758 or early 1759. The return of what is now called Halley's comet was observed after his death, This first observation of a "predicted" comet is manifestly one of the major successes of → celestial mechanics.

→ cometary; → orbit.

Of two bodies orbiting around a common barycenter, when the orbital period of one is an exact fraction, for example one-half or two-thirds, of the other.

→ commensurate; → orbit.

To cause a spacecraft to leave its operational orbit to enter a descent phase or to change course.

From → de- + → orbit.

Of a spacecraft, the act or process of departing from an operational orbit. → de-orbit.

Noun form of → de-orbit.

→ orbital element.

→ element; → orbit.

An → elliptical orbit with a high → eccentricity.

→ elongated; → orbit.

A region of the Galaxy whose boundaries are set by its calm and safe environment and access to the chemical materials necessary for building terrestrial planets similar to the Earth. → circumstellar habitable zone; → habitable zone.

→ galactic, → habitable; → zone.