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In the Solar System, many of the asteroid-sized moons have retrograde orbits, whereas all the large moons except Triton (the largest of Neptune's moons) have prograde orbits. [13] The particles in Saturn's Phoebe ring are thought to have a retrograde orbit because they originate from the irregular moon Phoebe.
An inclination of 0° means the orbiting body has a prograde orbit in the planet's equatorial plane. An inclination greater than 0° and less than 90° also describes a prograde orbit. An inclination of 63.4° is often called a critical inclination, when describing artificial satellites orbiting the Earth, because they have zero apogee drift. [3]
For orbits centered about planets other than Earth and Mars and for the dwarf planet Pluto, the orbit names incorporating Greek terminology are not as established and much less commonly used: This section needs additional citations for verification .
The inclination and semi-major axis are represented on the Y and X-axis, respectively. The satellites with inclinations below 90° are prograde, those above 90° are retrograde. The X-axis is labeled in terms of Saturn's Hill radius. The Gallic group is a dynamical grouping of the prograde irregular satellites of Saturn following similar orbits.
Two prograde moons of Saturn do not definitively belong to either the Inuit or Gallic groups. [1] S/2004 S 24 and S/2006 S 12 have similar orbital inclinations as the Gallic group, but have much more distant orbits with semi-major axes of ~400 Saturn radii and ~340 Saturn radii, respectively. [84] [13] [1]
The outer planets Jupiter, Saturn, Uranus and Neptune, compared to the inner planets Earth, Venus, Mars, and Mercury at the bottom right The four outer planets, called giant planets or Jovian planets, collectively make up 99% of the mass orbiting the Sun. [ h ] All four giant planets have multiple moons and a ring system, although only Saturn's ...
Five planets are going to be retrograde in the summer of 2024. Here are the dates for Mercury retrograde, Venus retrograde, Saturn retrograde, Neptune retrograde, Pluto retrograde and more.
The more distant planets retrograde more frequently, as they do not move as much in their orbits while Earth completes an orbit itself. The retrograde motion of a hypothetical extremely distant (and nearly non-moving) planet would take place during a half-year, with the planet's apparent yearly motion being reduced to a parallax ellipse.