SATURN IS OUR SOLAR SYSTE M’S RINGED WONDER. HERE’S WHAT EVERY ASTRONOMY ENTHUSIAST SHOULD KNOW ABOUT IT
SATURN: THE BASICS
Saturn is the sixth planet from the Sun, the second most massive world in the Solar System and the most distant that can easily be seen without a telescope. It orbits the Sun at an average distance of 1.43 billion kilometres (890 million miles) and appears to the naked eye as a moderately bright yellowish star. It’s only when seen through a telescope that the planet reveals its most impressive secret – a system of bright rings around its equator that present different views to Earth as Saturn circles the Sun once every 29.45 years. Unlike the rocky worlds of the inner Solar System, Saturn is a gas giant – a huge ball of lightweight gases that compress under their own weight to form a mostly liquid interior. With less than one-third the mass of its inner neighbour Jupiter, it keeps a weaker hold on its outer layers, which expand further, resulting in a planet that has roughly 80 per cent of Jupiter’s diameter, but an average density lower than water. What’s more, Saturn’s rapid rotation period of just under 10 hours and 34 minutes means that gas around its equator can attempt to escape its weak gravity, creating a substantial equatorial bulge that makes the planet’s diameter almost 12,000 kilometres (7,500 miles) greater measured across its equator than from pole to pole.
ATMOSPHERE
At first glance, Saturn’s atmosphere looks rather dull compared to the colourful storms of its inner neighbour Jupiter. However, this is more to do with its muted colours than a lack of activity. Orbiting further from the Sun, a combination of chilly temperatures and low pressures allow ammonia gas to condense in the uppermost cloud layer, forming a white haze that may conceal more colourful clouds below. Beneath the ammonia ice lies a deeper zone in which clouds are made of water ice, mixed for part of its depth with clouds of ammonium hydrosulfide ice. Deep beneath the surface, at atmospheric pressures 10 to 20 times greater than Earth’s, clouds of liquid water and ammonia droplets can form.
Clouds account for just a small proportion of Saturn’s atmospheric chemistry, and in general the atmosphere is dominated by gaseous molecular hydrogen, the lightest element in the universe. Hydrogen accounts for over 96 per cent of the atmosphere, with helium, the next lightest element, accounting for another 1 3.25 per cent. These gases condense into liquid roughly 9,000 kilometres (5,600 miles) below the surface, making Saturn’s gaseous outer layers about three times deeper than Jupiter’s.
Cold conditions in the upper atmosphere allow ammonia to condense and form bright, hazy clouds at pressures between roughly 0.4 and 1.7 times Earth’s atmospheric pressure.
As pressure increases further, ot
