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  2. Sphere of influence (astrodynamics) - Wikipedia

    en.wikipedia.org/wiki/Sphere_of_influence_(astro...

    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 ...

  3. Sphere of influence (black hole) - Wikipedia

    en.wikipedia.org/wiki/Sphere_of_influence_(black...

    The radius of the sphere of influence is called the "(gravitational) influence radius". There are two definitions in common use for the radius of the sphere of influence. The first [ 1 ] is given by r h = G M BH σ 2 {\displaystyle r_{h}={\frac {GM_{\text{BH}}}{\sigma ^{2}}}} where M BH is the mass of the black hole, σ is the stellar velocity ...

  4. Hill sphere - Wikipedia

    en.wikipedia.org/wiki/Hill_sphere

    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]

  5. Stellar dynamics - Wikipedia

    en.wikipedia.org/wiki/Stellar_dynamics

    This so-called sphere of influence is loosely defined by, up to a Q-like fudge factor ⁡, ⁡ / (+) /, hence for a Sun-like star we have, = (+) ⁡ / > [,] = (), i.e., stars will neither be tidally disrupted nor physically hit/swallowed in a typical encounter with the black hole thanks to the high surface escape speed = / = / from any solar ...

  6. Celestial mechanics - Wikipedia

    en.wikipedia.org/wiki/Celestial_mechanics

    Astrometry is a part of astronomy that deals with measuring the positions of stars and other celestial bodies, their distances and movements. Astrophysics; Celestial navigation is a position fixing technique that was the first system devised to help sailors locate themselves on a featureless ocean.

  7. Celestial spheres - Wikipedia

    en.wikipedia.org/wiki/Celestial_spheres

    Taking the distance of the Sun as 1,266 Earth radii, he was forced to place the sphere of Venus above the sphere of the Sun; as a further refinement, he added the planet's diameters to the thickness of their spheres. As a consequence, his version of the nesting spheres model had the sphere of the stars at a distance of 140,177 Earth radii. [34]

  8. Sphere of influence (disambiguation) - Wikipedia

    en.wikipedia.org/wiki/Sphere_of_influence...

    Sphere of influence may refer to: Sphere of influence (astrodynamics), the area, typically spherical, around a celestial body, e.g. a star, in which that body is the biggest gravitational influence; Sphere of influence (black hole), a region around a black hole in which the gravitation of the black hole dominates that of the host bulge

  9. Empirical evidence for the spherical shape of Earth - Wikipedia

    en.wikipedia.org/wiki/Empirical_evidence_for_the...

    The only shape that casts a round shadow no matter which direction it is pointed is a sphere, and the ancient Greeks deduced that this must mean Earth is spherical. [ 8 ] The effect could be produced by a disk that always faces the Moon head-on during the eclipse, but this is inconsistent with the fact that the Moon is only rarely directly ...