Hill Sphere Definition and Illustration

Word of the Week: Hill Sphere

The region around a planetary body where its own gravity (compared to that of the Sun or other nearby bodies) is the dominant force in attracting satellites, such as spacecraft or moons.

Because Bennu has a radius of only 250 meters, its Hill sphere is small compared to that of a planet or star. While the radius of Earth’s Hill Sphere is ~1.5 million km, the radius of Bennu’s is ~29.5 km.

Credit: University of Arizona


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