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

In a system where no external forces are present, every action force is always opposed by an equal and opposite reaction.

→ Newton; → third; → law; → motion.

A → tumbling motion of an → asteroid. See also → tumbling asteroid.

→ non-; → principal axis; → rotational; → motion.

The proper motion of a star due to the effect of the Sun's motion relative to the → local standard of rest.

→ parallactic; → motion.

1) The true motion of a star with respect to the Local Standard of Rest. → proper motion.
2) The motion of a cosmological object other than the apparent recession caused by the expansion of the Universe.

→ peculiar; → motion.

Any motion that recurs in identical forms at equal intervals of time.

→ periodic; → motion.

The motion of a hypothetical machine which, once set in motion, will go on for ever without any losses due to → friction or other forms of → dissipation of energy and without receiving any external energy.

→ perpetual; → motion.

The motion of a torque free rotating rigid body in space, in general whose angular velocity vector precesses regularly about the constant angular momentum factor.

After Louis Poinsot (1777-1859), French physicist and mathematician. He was the inventor of geometrical mechanics, showing how a system of forces acting on a rigid body could be resolved into a single force and a couple.

The irregularly varying motion of the Earth's pole of rotation with respect to the Earth's crust.

→ polar; → motion.

A rotational or orbital movement that is the same as most bodies within a celestial system. In the solar system, the apparent eastward motion of a celestial body on the celestial sphere. Opposed to → retrograde motion. Same as → direct motion.

From → pro- "forward" + grade, from L. gradi "to go, step, walk;" → motion.

Jonbeš, → motion; farârow, from farâ- "forward," → pro-, + row present stem of raftan "to go, walk;" Mid.Pers. raftan, raw-, Proto-Iranian *rab/f- "to go; to attack."

1) The act of promoting someone to a higher job, grade, or rank, or the fact of being so promoted.
2) Support or encouragement of the progress, growth, or acceptance of something.
3) An act, event, or offer that helps to increase interest in or demand for something (FreeDictionary.com).

Verbal noun of → promote.

Farkašan, literally "draw forward, pull up," from far-, variant of farâ-, → pro-, + kašan "drawing, pull," from kaš present stem of kašidan, → galaxy, + noun suffix -an.

The apparent motion of a star across the sky (not including a star's parallax), arising from the star's velocity through space with respect to the Sun. Proper motion is usually tabulated in star catalogs as changes in right ascension and declination per year or century. See also: → proper motion distance.

→ proper; → motion.

The distance derived from the → proper motion of an object. If an object has a known → transverse velocity  u, and has an observed angular motion of dθ/dt, then the proper motion distance is defined as: d = u/(dθ/dt).

→ proper; → motion; → distance

In a dynamical system, a form of motion that is regular but never exactly repeating. Quasiperiodic motion appears when the system contains two or more incommensurate frequencies.

→ quasi-; → periodic; → motion.

A motion away from or toward a central point or axis.

→ radial; → motion.

The agitated motion of molecular, atomic, or → subatomic particles in all possible directions at any temperature, except at → absolute zero, where → thermal motion would cease.

→ random; → thermal; → motion.

The orbital motion or rotation of a solar system body in a clockwise direction (East to West) when viewed from the north pole of the ecliptic. It is a motion opposed to the → direct motion of the great majority of solar system bodies.

→ retrograde; → motion.

Of a → rigid body, a motion in which there are always two points of the body which remain motionless.

→ rotational; → motion.

The motion of a body subjected to a restraining force which is directly proportional to the displacement from a fixed point in the line of motion. The equation of simple harmonic motion is given by x = A sin(ωt + θ₀), where x is the body's displacement from equilibrium position, A is the → amplitude, or the magnitude of harmonic oscillations, ω is the → angular frequency, t is the time elapsed, and θ₀ is the → initial phase angle.

→ simple; → harmonic; → motion.

The velocity and direction of motion of a star or celestial object with respect to the Local Standard of Rest. Same as → peculiar velocity.

→ space; → motion.

Apparent proper motion exceeding the velocity of light seen toward certain astronomical objects, such as the jets of radio galaxies and quasars. However, these jets are not actually moving at speeds in excess of the speed of light: the apparent superluminal motion is a projection effect caused by objects moving near the speed of light and at a small angle to the line of sight.

→ super-; luminal, from → lumen; → motion.

Jonbeš, → motion; abar→ super-; nur, → light.