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The Hill sphere is a common model for the calculation of a gravitational sphere of influence. It is the most commonly used model to calculate the spatial extent of gravitational influence of an astronomical body ( m ) in which it dominates over the gravitational influence of other bodies, particularly a primary ( M ). [ 1 ]
A sphere of influence (SOI) in astrodynamics and astronomy is the oblate spheroid-shaped region where a particular celestial body exerts the main gravitational influence on an orbiting object. This is usually used to describe the areas in the Solar System where planets dominate the orbits of surrounding objects such as moons , despite the ...
The Hill sphere (gravitational sphere of influence) of the Earth is about 1,500,000 kilometers (0.01 AU) in radius, or approximately four times the average distance to the Moon. [12] [nb 2] This is the maximal distance at which the Earth's gravitational influence is stronger than the more distant Sun and planets. Objects orbiting the Earth must ...
In geometry, the major axis of an ellipse is its longest diameter: a line segment that runs through the center and both foci, with ends at the two most widely separated points of the perimeter. The semi-major axis ( major semiaxis ) is the longest semidiameter or one half of the major axis, and thus runs from the centre, through a focus , and ...
A sphere (top), rotational ellipsoid (left) and tri-axial ellipsoid (right) The mean radius in astronomy is a measure for the size of planets and small Solar System bodies . Alternatively, the closely related mean diameter ( D {\displaystyle D} ), which is twice the mean radius, is also used.
Near-rectilinear means that some segments of the orbit have a greater curvature than those of an elliptical orbit of the same maximum diameter, and other segments have a curvature less than that of an elliptical orbit of the same maximum diameter (taking maximum diameter as that of the smallest circle that contains the whole of the orbit).
In celestial mechanics, the Roche limit, also called Roche radius, is the distance from a celestial body within which a second celestial body, held together only by its own force of gravity, will disintegrate because the first body's tidal forces exceed the second body's self-gravitation. [1]
Cited diameter is that of the Sun's Hill sphere; the region of its gravitational influence. [28] Local Interstellar Cloud: 9.2 pc 2.84×10 14: Interstellar cloud of gas through which the Sun and a number of other stars are currently travelling. [29] Local Bubble: 2.82–250 pc 8.70×10 13 –7.71×10 15