The rings

Uranus has a number of rings around it. These were discovered by chance in 1977 when Uranus appeared to pass in front of the faint star SAO158687 in Libra, as seen from Earth. Such an event is called an occultation. The rings temporarily interrupted light from the star and pulses of starlight were seen each side of the planet, suggesting there was something around the planet. In 1986, Voyager 2 confirmed the existence of a ring system containing nine main rings with two smaller ringlets. The ring system lies in the Uranian equatorial plane, circling Uranus between 38 000 km and 51 140 km from its centre. Their overall diameter is over 100 000 km.

The rings are faint and composed of particles ranging in size from fine dust to several metres in diameter. Voyager 2 found that the gaps between

Table 11.3 Uranus' rings

Ring

Distance (km)

Width (km)

0 0

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