cassini division

noun Astronomy.

1. a 3000-mile (4800-km) wide dark region that separates the middle and outermost rings of the planet Saturn.

1. The large gap between Saturn’s two most prominent rings (the outer A ring and middle B ring), appearing as a dark void but actually containing small amounts of opaque material. It is formed as a result of particles being removed from the area by the gravitational pull of Mimas, one of the smaller of Saturn’s moons. The division is named after the Italian astronomer, Giovanni D. Cassini (1625-1712), who discovered it in 1675.