Most people probably know Saturn from a very young age, mostly because of its magnificent rings depicted in many encyclopedias, books and television shows. Saturn has other interesting features though, like its lower-than-water density and oblate spheroid shape.
Saturn was known to humans since classical antiquity and has many names in different languages, but name “Saturn” comes from the Roman god of agriculture. It is the sixth planet from the Sun, the second in size after Jupiter, weighing 95 times more than Earth and with radius 9 times larger than Earth’s.
Saturn orbits the Sun at 9.5 astronomical units (AUs) i.e. it is almost 9 times farther away from the Sun than Earth is. It needs 29.5 years to orbit our star and about 10 hours and 30 minutes to rotate around its own axis, with some regions rotating faster than others, as in all gas giants. The fast rotation and its composition makes Saturn flattened at the poles and it has a bulge at the equator.
Speaking of gas giants, Saturn is of course one of the four, the other three being Jupiter, Uranus and Neptune. Its atmosphere is made mostly of hydrogen (96%) and helium (3%). This makes Saturn the least dense planet in the Solar system, less dense than water even. Deeper under the atmosphere, under all that pressure, gases turn to liquids, and even deeper down there is a hydrogen liquid-metallic layer. At the centre, there’s a rocky core estimated to be anywhere between 9 and 22 times heavier than the whole Earth.
At the core, temperatures reach 11,700 degrees Celsius and Saturn radiates 2.5 times more energy than it receives from the Sun, mostly due to slow gravitational compression, but some of that energy is possibly produced by “raining” helium droplets. Helium moves toward the inner layers and the friction between helium and less dense hydrogen molecules produces extra heat, at the same time leaving the planet’s atmosphere with less helium than it was anticipated based on 3:1 hydrogen to helium ratio in the Sun and Jupiter.
Winds on Saturn are the second strongest after Neptune’s, reaching up to 1800 km/h. Temperatures are usually around -185 degrees Celsius, with an exception of the warm vortex at the south pole, where temperatures reach -122 degrees Celsius. It is a one-of-a-kind phenomenon in the Solar system. A vortex that could have formed billions of years ago is larger than Earth and has winds clocked at about 550 km/h.
South pole vortex is has its north pole counterpart in the form of a hexagonal wave pattern with sides at about 13,000 km each, its origin unknown.
Boasting the largest and most visible ring system of all gas giants, Saturn is surely the planet with the most recognizable feature of them all. Rings are spread from 6,600 to 120,700 kilometres above planet’s equator, thick only 20 metres on average. Nine rings and three discontinuous arcs are made mostly of water and range from tiny dust particles to 10 metre chunks. Old a few hundred million years, rings either formed from a destroyed moon or are leftover from the material the planet was formed from. Saturn has 62 moons, some of which shepherd the ring particles and keep them together. The largest moon is Titan, the only moon in the Solar system with dense atmosphere and the second largest moon after Jupiter’s Ganymede. Although first observed by Galileo in 1610 who had thought they were moons, Saturn’s rings were first identified by Huygens who also discovered Titan.
Saturn was visited by four space probes. Pioneer 11, Voyager 1 and Voyager flew by the planet, while Cassini-Huygens probe is still in orbit around Saturn.
All images credited to NASA