Hill sphere


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Hill sphere

The spherical region around a planet (or satellite) within which that body dominates the motion of particles. Once the core of a planet exceeds a mass of about 1023 kg, it gravitationally attracts gas from the Hill sphere and is able to form an atmosphere in this way. Jupiter's Hill sphere, for example, had a volume about 1000 times greater than that of the Earth.
References in periodicals archive ?
"The moon is within Earth's 'Hill sphere,' the volume of space in which Earth's gravity is the dominant influence," he says.
(In contrast, uncaptured NEOs often zip by at tens of kilometers per second.) Then they "fall" into the Hill sphere, the dynamical netherland where our planet's gravitational influence exceeds that of the Sun.
"They rattle around the Hill sphere with all sorts of trajectories until they find a way out.
At each level, a satellite has to fit well within its host's Hill sphere. (You might appreciate the name.) This is where the gravitational force between the two is stronger than the influence of the next object up.