shepherd satellite

American  

noun

1. a small moon orbiting near a planetary ring, whose gravitational pull helps confine the ring and the ring's extent.

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shepherd satellite Scientific  

/ shĕp′ərd /

1. A moon that orbits near the edge of a planetary ring, stabilizing the ring's particles through gravitational pull and confining the ring to a sharply defined band. For example, the moons of Uranus known as Cordelia and Ophelia are shepherd satellites that constrain Uranus's rings to a narrow band. It is believed that the gravity of the fast-moving inner satellite Cordelia causes the particles of the inner ring to speed up and move to outer orbits, while at the same time the gravity of the slower, outer satellite Ophelia decelerates outer particles, pushing them inward. The result is a compressed, well-defined ring.

2. Also called shepherd moon

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Example Sentences

Traveling to the farm, where the European-style cheeses are produced on 120 rolling acres, is not a prerequisite: In addition to 20 weekly farmers’ markets, Mr. Wajswol’s crumbly, cave-aged Cheddars and about 29 other varieties are for sale at Valley Shepherd satellite stores in Philadelphia, Brooklyn and Manhattan.

From New York Times