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Supercomputers crack Saturn's ice-cold ring

And explain Uranus's dark band

Supercomputing boffins may have solved the mystery of how it came to be that Saturn's rings are so bright in the night sky.

The planet's rings are largely made of ice, making them so visible that Galileo first spotted them using a primitive telescope in the early 1600s. Meanwhile, similar ring systems around Uranus and Neptune are made of rock and are so dark they were only spotted by visiting probes in the 1970s and 1980s.

Astronomers now think they've worked out how these different ring systems came into being and think the Great Bombardment is to blame. During this period, around four billion years ago, large numbers of Pluto-sized rocks from the Kuiper Belt encircling the Solar System fell towards the Sun and smashed into planets on their the way in.

Many of the craters we see on the Moon are the result of this bombardment, for example. As for the gas giants, their gravitational forces were great enough to tear apart the passing objects.

Using supercomputers at the National Astronomical Observatory of Japan, astronomers found that as these bodies got close to Neptune and Uranus, the gravitational forces involved shredded the huge rocks and the remains formed the dark rings that encircle those alien worlds.

Saturn is only half as dense as its two cousins further out. As such the forces involved were strong enough to pull the ice off these asteroids and rip off chunks of rock, but enough not to cause significant destruction to the space boulders. Some of the ice and rock stayed in orbit, which is why Saturn has more than 60 moons, more than double the number found in the further gas giants.

"These findings illustrate that the rings of giant planets are natural by-products of the formation process of the planets in our solar system," the team noted this week.

"This implies that giant planets discovered around other stars likely have rings formed by a similar process. Discovery of a ring system around an exoplanet has been recently reported, and further discoveries of rings and satellites around exoplanets will advance our understanding of their origin." ®


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