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  • Elizabeth Cocking

Did you know? Saturn's Rings

This month . . . . Saturn’s rings. One of the most majestic sights in the night sky.

Saturn’s rings are enormous, but they are also extremely thin. The major rings have a diameter of 270,000 km yet their thickness does not exceed 100 metres. The entire ring system spans nearly 26,000,000 km when the faint outer rings are included.

The rings appear to “vanish” every 15 years or so when they are edge-on as seen from Earth. This is known as a “ring plane crossing”. The next one will be in 2025. After that the south side of Saturn’s rings will gradually increase to a maximum inclination of 27 degrees and by May 2032 will be very well presented. Ring plane crossings are good times to discover new Saturnian moons and faint outer rings.

Galileo was the first to observe the rings of Saturn in 1610 but his telescope was not strong enough to identify them as such. He described them as Saturn's "ears". In 1612 he found they had “disappeared”, they were, in fact, edge-on from Earth's perspective. Galileo inadvertently became the first person to observe a Saturn ring plane crossing.

The rings are named alphabetically based on when they were discovered. To date the rings have only reached G but working from the planet out, the letters go D, C, B, A, F, G, E.

Most of these rings are very close together, with the exception of B and A. These rings are 4,700 km apart. This gap is known as the Cassini Division after the Italian astronomer Giovanni Cassini who discovered it in 1675. Image above: NASA/JPL-Caltech/Space Science Institute, published: November 16, 2016

If you want to see the rings you’d better hurry !. Known as “ring rain” they are being pulled onto Saturn’s surface by gravity. Astronomers believe the rings will completely disappear in 100-300 million years time.

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