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One possible explanation for the braking is the interaction of the protostar's magnetic field with the stellar wind. In the case of the Solar System, when the planets' angular momenta are compared to the Sun's own, the Sun has less than 1% of its supposed angular momentum. In other words, the Sun has slowed down its spin while the planets have not.
The blue planet feels only an inverse-square force and moves on an ellipse (k = 1). The green planet moves angularly three times as fast as the blue planet (k = 3); it completes three orbits for every orbit of the blue planet. The red planet illustrates purely radial motion with no angular motion (k = 0).
In Mercury's case, the planet completes three rotations for every two revolutions around the Sun, a 3:2 spin–orbit resonance. In the special case where an orbit is nearly circular and the body's rotation axis is not significantly tilted, such as the Moon, tidal locking results in the same hemisphere of the revolving object constantly facing ...
The common noun ‘moon’ (not capitalized) is used to mean any natural satellite of the other planets. Tidal force is the combination of out-of-balance forces and accelerations of (mostly) solid bodies that raises tides in bodies of liquid (oceans), atmospheres, and strains planets' and satellites' crusts.
When analysed in a rotating reference frame of the planet, centrifugal force causes rotating planets to assume the shape of an oblate spheroid. Main article: Absolute rotation Three scenarios were suggested by Newton to answer the question of whether the absolute rotation of a local frame can be detected; that is, if an observer can decide ...
Stars and planets rotate in the first place because conservation of angular momentum turns random drifting of parts of the molecular cloud that they form from into rotating motion as they coalesce. Given this average rotation of the whole body, internal differential rotation is caused by convection in stars which is a movement of mass, due to ...
This illustration shows the oblate appearance of the star Achernar caused by rapid rotation.. Stellar rotation is the angular motion of a star about its axis. The rate of rotation can be measured from the spectrum of the star, or by timing the movements of active features on the surface.
All eight planets in the Solar System orbit the Sun in the direction of the Sun's rotation, which is counterclockwise when viewed from above the Sun's north pole. Six of the planets also rotate about their axis in this same direction. The exceptions – the planets with retrograde rotation – are Venus and Uranus.