Composition and Climate[]
Saturn is the outer of Sol's two gas giants - massive worlds composed primarily of hydrogen and helium. It has no solid surface. Instead, it has a steadily thickening hydrogen/helium atmosphere which eventually becomes liquid metallic hydrogen as depth increases. At the center of the planet there is likely a solid rocky core. Circulation in the liquid metallic hydrogen layer is the probable source of Saturn's magnetic field. Saturn's aurorae are the tallest in the Solar system, reaching over 1000 kilometers in height.
Saturn's poles are ringed with huge rotating cloud structures. In particular the north pole is surrounded by a giant hexagonal structure and the pole itself is the center of a powerful vortex. The south pole has a warm polar vortex, unique in the Solar system. Temperatures in this vortex are over 60 K warmer than the rest of the planet, making it the warmest spot on Saturn. Elsewhere in its atmosphere can be found strong storms that can persist for months. One of the most spectacular storm features is the periodic 'Great White Spot', a massive storm that erupts about once every Saturnian year (30 Earth years) in the northern hemisphere during summer. Similar but smaller outbreaks of large white storms can occur with greater frequency. Winds on Saturn can reach speeds of 1800 km/h, second only to Neptune.
Saturn's seasons are driven not only by its axial tilt as with most planets, but also by its rings. The rings block sunlight to the autumnal/winter hemisphere, making it even darker than it would otherwise be. This can lead to dramatic seasonal effects, including a subsidence of cloud levels across the winter hemisphere, after which the now-clear air takes on a bright blue color.[1]
Rings[]
Saturn's majestic rings are easily its most prominent feature. The rings are tens of thousands of kilometers wide but average only 20 meters thick. They are composed mainly of water ice and modest amounts of carbon. The particles in the rings range in size from dust grains to chunks of material in tens of meters wide or more. The main ring disk has several gaps carved out by gravitational perturbations and by small moons orbiting among the rings. Moons orbiting in or near the rings cause ripples, waves, and spirals to form in the rings due to their gravitational effects. Tiny moonlets also exist embedded in the rings, and along the forward edge of the B ring material has piled up into vertical structures a few kilometers in height. It is not known exactly how old the rings are, but they may be nearly as old as the planet itself, having formed along with or shortly after the rest of the Saturn system.
Beyond the main ring disk are other, fainter rings. Among these is the E ring, the outermost ring in Saturn's equatorial ring system. Unlike the other rings it is very thick and diffuse, and composed of primarily microscopic particles of ice. When backlit by the sun the ring becomes visible and has a noticeable blue color. The source of the E ring is material erupting from the cryovolcanic geysers near the south pole of Enceladus. Material erupting from the moon escapes its weak gravity and goes into orbit around Saturn, thus forming the ring. Material from this ring accumulates on the moons that pass through it, giving Tethys its blue-tinted leading hemisphere and smoothing out the features on moons such as Telesto and Helene.
The outermost of these faint rings is the very large and diffuse Phoebe ring, not discovered until 2009. The ring occupies roughly the same region of space as the moon Phoebe, hence its name, and is aligned with Saturn's orbital plane. The ring is over a million kilometers thick and perhaps seven million kilometers wide from inner to outer edge. Impacts with Phoebe are thought to be the source of the ring's material. This material is partly responsible for the strong bicoloration on Iapetus and probably initiated that process.
Diagram showing Saturn's internal composition and the nomenclature of its rings
Diagram showing the nomenclature of Saturn's rings and the positions of its inner satellites
Moons[]
Saturn has a system of 274 known moons. Several of these are large, round satellites which rank among the largest moons in the Solar system. The largest of these, Titan, comprises 90% of the mass orbiting Saturn, and is the second largest moon in the Solar system. It also is the only moon with a thick atmosphere and the only known world other than Earth to have stable bodies of liquid on its surface. Among Saturn's other large moons are Iapetus, Rhea, Dione, Tethys, Enceladus, and Mimas. All of these orbit near Saturn and in its equatorial plane except for Iapetus, which orbits at a greater distance and with an inclined orbit. It is notable for having a strong two-toned appearance, with half of the moon being very dark and the other half being very light, and for its tall equatorial mountain ridge. Enceladus is also a noteworthy moon: it is the brightest (most reflective) object in the Solar system, reflecting over 99% of the light that strikes it; it also has powerful cryovolcanic geysers located near its south pole, in fissures known as 'Tiger Stripes'. These geysers are the source of Saturn's E ring.
Also among the near-Saturn moons are many small satellites. Some of these satellites shepherd ring material. There are five of these 'shepherd moons': Pan, Daphnis, Atlas, Prometheus, and Pandora. They are responsible for sculpting many of the gaps and edges in the rings, specifically the Encke gap, Keeler gap, A ring, and F ring respectively (the latter being shepherded by both Prometheus and Pandora). Two other small moons, Janus and Epimetheus, form a co-orbital pair; that is, they share almost exactly the same orbit. They approach each other every four years and their gravitational interaction causes them to switch orbits instead of colliding. Methone, Anthe, and Pallene are small moons that orbit between Mimas and Enceladus. The Saturn system uniquely features trojan moons, moons that orbit at the L4 or L5 Lagrange point of a much larger moon. Telesto and Calypso are trojans of Tethys, while Helene and Polydeuces are trojans of Dione.
While Saturn has dozens of other, irregular satellites, two are especially noteworthy. First is Hyperion, which orbits just beyond Titan. It is nearly 300 kilometers wide yet extremely irregular in shape. It has a reddish, spongey appearance, and a very low density, indicating that it is largely porous. It also has unpredictable rotational behavior, essentially tumbling chaotically through space. The second noteworthy outer irregular satellite is Phoebe. It is over 200 kilometers wide, has a retrograde orbit, rotates every 9.3 hours, and is the source of Saturn's Phoebe ring. It is nearly spherical in shape and relatively dense. Its dark surface is composed of water ice, carbon dioxide, phyllosilicates, and organics. Phoebe is most likely a captured centaur and probably originated in the Kuiper Belt.
Saturn's main moons: Mimas, Enceladus, Tethys, Dione, Rhea, Titan and Iapetus
Titan's shadow[]
This content is on the SE Planetarium where on the time 2009.08.03 02h11m54.23s is where Titan's shadow is on that time.
- ↑ This article has been adapted from the Space Engine ingame wiki.
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