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

A time interval over which an orbit precesses by 2π radians in its plane.

→ precession; → time.

Of or pertaing to → precession.

→ precession; → -al.

The path of either → celestial poles around the → ecliptic pole due to the → precession of equinox. It takes about 26,000 years for the celestial pole to complete path.

→ precessional; → circle.

1) The act of receding, going back, or withdrawing.
2) Economics: A period of an economic contraction, sometimes limited in scope or duration (Dictionary.com).

From Fr. récession "a going backward, a withdrawing," from L. recessionem "a going back," noun of action from p.p. stem of recedere "to go back, fall back; withdraw, retire," from → re- "back" + cedere "to go," → process.

Duršod, from dur, → remote, + šod "going," past stem of šodan "to go, to become," → change. Vâraveš, from vâ-, → re-, + raveš verbal noun of raftan "to go," → method.

The velocity with which an object moves away from another object or a reference point.

→ recession; → velocity.

A → general relativistic phenomenon in which the line joining the → apsides of an orbit gradually rotates in a → prograde direction. Also called the → orbital precession and → perihelion precession. Although the general relativistic precession of Mercury's orbit is extremely small, the similar precession observed in the orbit of the → binary pulsar PSR B1913+16 amounts to 4.23 degrees per year, i.e. 36,000 times greater than the → advance of perihelion of Mercury.

→ relativistic; → precession.

The change in the direction of the → rotation axis of a → pulsar in a → binary pulsar. In such a system, → geodetic precession leads to a relativistic → spin-orbit coupling, analogous of → spin-orbit coupling in atomic physics. In consequence, the pulsar spin precesses about the total → angular momentum, changing the relative → orientation of the pulsar toward Earth (Damour & Ruffini, 1974). As a result, the angle between the pulsar → rotation axis and our → line of sight changes with time, so that different portions of the emission beam can be observed leading to changes in the measured pulse profile. In extreme cases, the precession may even move the beam out of our line of sight and the pulsar may disappear as predicted for PSR 1913+16 for the year 2025.

→ relativistic; → spin; → precession.