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Because Neptune is not a solid body, its atmosphere undergoes differential rotation. The wide equatorial zone rotates with a period of about 18 hours, which is slower than the 16.1-hour rotation of the planet's magnetic field. By contrast, the reverse is true for the polar regions where the rotation period is 12 hours.
^ The inclination of the body's equator from its orbit. ^ At pressure of 1 bar ^ At sea level ^ The ratio between the mass of the object and those in its immediate neighborhood. Used to distinguish between a planet and a dwarf planet. ^ This object's rotation is synchronous with its orbital period, meaning that it only ever shows one face to ...
Venus rotates clockwise, and Uranus has been knocked on its side and rotates almost perpendicular to the rest of the Solar System. The ecliptic remains within 3° of the invariable plane over five million years, [ 2 ] but is now inclined about 23.44° to Earth's celestial equator used for the coordinates of poles.
Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. [a] Neptune orbits the Sun once every 164.8 years at an average distance of 30.1 astronomical units (4.50 × 10 9 km).
The planetary orbit is not a circle with epicycles, but an ellipse. The Sun is not at the center but at a focal point of the elliptical orbit. Neither the linear speed nor the angular speed of the planet in the orbit is constant, but the area speed (closely linked historically with the concept of angular momentum) is constant.
For gaseous or fluid bodies, such as stars and giant planets, the period of rotation varies from the object's equator to its pole due to a phenomenon called differential rotation. Typically, the stated rotation period for a giant planet (such as Jupiter, Saturn, Uranus, Neptune) is its internal rotation period, as determined from the rotation ...
Neptune's rings had been observed from Earth many years prior to Voyager 2 's visit, but the close inspection revealed that the ring systems were full circle and intact, and a total of four rings were counted. [4] Voyager 2 discovered six new small moons orbiting Neptune's equatorial plane, dubbed Naiad, Thalassa, Despina, Galatea, Larissa and ...
Since the word "inclination" is used in exoplanet studies for this line-of-sight inclination, the angle between the planet's orbit and its star's rotational axis is expressed using the term the "spin-orbit angle" or "spin-orbit alignment". [5] In most cases the orientation of the star's rotational axis is unknown.