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The term retrograde is from the Latin word retrogradus – "backward-step", the affix retro-meaning "backwards" and gradus "step". Retrograde is most commonly an adjective used to describe the path of a planet as it travels through the night sky, with respect to the zodiac, stars, and other bodies of the celestial canopy. In this context, the ...
Six of the planets also rotate about their axis in this same direction. The exceptions – the planets with retrograde rotation – are Venus and Uranus. Venus's axial tilt is 177°, which means it is rotating almost exactly in the opposite direction to its orbit. Uranus has an axial tilt of 97.77°, so its axis of rotation is approximately ...
The average distance between Neptune and the Sun is 4.5 billion km (about 30.1 astronomical units (AU), the mean distance from the Earth to the Sun), and it completes an orbit on average every 164.79 years, subject to a variability of around ±0.1 years. The perihelion distance is 29.81 AU, and the aphelion distance is 30.33 AU.
No, Mercury isn't the only planet that goes retrograde.
Book III describes his work on the precession of the equinoxes and treats the apparent movements of the Sun and related phenomena. Book IV is a similar description of the Moon and its orbital movements. Book V explains how to calculate the positions of the wandering stars based on the heliocentric model and gives tables for the five planets.
from Latin periodus (“complete sentence, period, circuit”), from Ancient Greek períodos (“cycle, period of time”) farer: ion: from Greek neuter present participle of ienai, meaning "to go". samestead: isotope: Greek roots isos (ἴσος "equal") and topos (τόπος "place"), meaning "the same place"
These expressions are for the so-called mean obliquity, that is, the obliquity free from short-term variations. Periodic motions of the Moon and of Earth in its orbit cause much smaller (9.2 arcseconds ) short-period (about 18.6 years) oscillations of the rotation axis of Earth, known as nutation , which add a periodic component to Earth's ...
The term does not refer to shape; Triton, for example, is a round moon but is considered irregular due to its orbit and origins. As of February 2024 [update] , 228 irregular moons are known, orbiting all four of the outer planets ( Jupiter , Saturn , Uranus , and Neptune ).