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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.
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.
The convention is that the normal orbit is prograde, an orbit in the same direction as the planet rotates. Inclinations greater than 90° describe retrograde orbits (backward). Thus: An inclination of 0° means the orbiting body has a prograde orbit in the planet's equatorial plane.
The prograde satellites consist of the Himalia group and three others in groups of one. The retrograde moons are grouped into the Carme, Ananke and Pasiphae groups. Saturn has 146 moons with known orbits; 66 of them have received permanent designations, and 63 have been named. Most of them are quite small.
Retrograde (backward) and prograde (forward) are observed as though the stars revolve around the Earth. Ancient Greek astronomer Ptolemy in 150 AD believed that the Earth was the center of the Solar System and therefore used the terms retrograde and prograde to describe the movement of the planets in relation to the stars. Although it is known ...
The new discovery increases the moons orbiting the "jewel of our solar system" to 82, surpassing Jupiter
Orbits around the L 1 point are used by spacecraft that want a constant view of the Sun, such as the Solar and Heliospheric Observatory. Orbits around L 2 are used by missions that always want both Earth and the Sun behind them. This enables a single shield to block radiation from both Earth and the Sun, allowing passive cooling of sensitive ...
The specific example discussed is of a satellite orbiting a planet, but the rules of thumb could also apply to other situations, such as orbits of small bodies around a star such as the Sun. Kepler's laws of planetary motion: Orbits are elliptical, with the heavier body at one focus of the ellipse. A special case of this is a circular orbit (a ...