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Retrograde motion in astronomy is, in general, orbital or rotational motion of an object in the direction opposite the rotation of its primary, that is, the central object (right figure). It may also describe other motions such as precession or nutation of an object's rotational axis .
Asteroids and Kuiper Belt objects (including Pluto) exhibit apparent retrograde motion. This motion is normal for the planets, and so is considered direct motion. However, since Earth completes its orbit in a shorter period of time than the planets outside its orbit, it periodically overtakes them, like a faster car on a multi-lane highway.
in apparent retrograde motion [2] visible almost all night – rising around sunset, culminating around midnight, and setting around sunrise [3] at the point in its orbit where it is roughly closest to Earth, making it appear larger and brighter [4] nearly completely sunlit; the planet shows a full phase, analogous to a full moon [5]
The symbol for retrograde motion is ℞, a capital 'R' with a tail stroke. [23] [24] [25] An 'R' with a tail stroke was used to abbreviate many words beginning with the letter 'R'; in medical prescriptions, it abbreviated the word recipe [26] (from the Latin imperative of recipere "to take" [27]), and in missals, an R with a tail stroke marked ...
Apparent retrograde motion is the periodic, apparently backwards motion of planetary bodies when viewed from the Earth (an accelerated reference frame). Satellite is an object that orbits another object (known as its primary). The term is often used to describe an artificial satellite (as opposed to natural satellites, or moons).
Marsyas has a semimajor axis that puts it very near the 3:1 mean-motion resonance with Jupiter at 2.5 au. This resonance has been shown to be a source for near-Earth asteroids on low-inclination orbits to evolve onto retrograde orbits.
This makes retrograde minor planets the rarest group of all. High-inclination asteroids are either Mars-crossers (possibly in the process of being ejected from the Solar System) or damocloids. Some of these are temporarily captured in retrograde resonance with the gas giants. [20]
The studies showed that the asteroid has a mean diameter of 1.1 km, assuming that 1950 DA is a retrograde rotator. [18] Optical lightcurve analysis by Lenka Šarounová and Petr Pravec shows that its rotation period is 2.1216 ± 0.0001 hours.