Saturn is the second largest among the planets of the solar system. Its equatorial diameter is only slightly smaller than that of Jupiter, but Saturn is more than three times as massive as Jupiter and has a very low average density – about 0.7 g / cm3. The low density is due to the fact that the giant planets are composed mainly of hydrogen and helium. Moreover, in the bowels of Saturn, the pressure does not reach such high values as on Jupiter, so the density of matter there is less. Spectroscopic studies found some molecules in Saturn’s atmosphere. The surface temperature of the clouds on Saturn is close to the melting point of methane (-184 ° C), of which the cloud layer of the planet most likely consists of solid particles. Dark bands elongated along the equator, also called belts, and bright zones are visible through the telescope, but these details are less contrasted than on Jupiter, and individual spots in them are much less common. Saturn is surrounded by rings that are clearly visible through a telescope in the form of “ears” on both sides of the planet’s disk. They were noticed by Galileo in 1610. The rings of Saturn are one of the most amazing and interesting formations in the solar system. A flat ring system encircles the planet around the equator and never touches the surface. The rings are divided into three main concentric zones, delimited by narrow slits: the outer ring A, the middle B (the brightest), the inner ring C, rather transparent, “crepe”, its inner edge is not sharp. The faintest parts of the inner ring closest to the planet are denoted by D. The existence of the almost transparent outermost ring D ’is also found.
Through all the rings of Saturn, stars shine through. The rings revolve around Saturn, and the speed of movement of the internal parts is greater than the external. The rings of Saturn are not continuous, but represent a flat system of an infinite number of small satellites of the planet. The plane of the rings practically coincides with the plane of the equator of Saturn and has a constant inclination to the plane of the orbit, equal to approximately 27 °. Depending on the position of the planet in orbit, we see rings on one side or the other. The full cycle of changing their appearance is completed within 29.5 years – this is the period of Saturn’s revolution around the Sun. From time to time, rings for a short time cease to be visible in medium-sized telescopes. This happens when the plane of the rings passes exactly through the Sun and the side surface is devoid of bright illumination, or when the rings face the observer with an “edge” and look like an extremely thin strip visible only with the largest telescopes. The thickness of the rings, according to modern data, is about 3.5 km. It is very small compared to their diameter, which is 275 thousand km along the outer edge of ring A. Particle sizes are not completely determined. Radio astronometric observations indicate the presence in the rings of many particles with a size of at least several centimeters. The possibility of the presence of even larger particles in the rings of Saturn, as well as dust, is not excluded.
The infrared spectra of Saturn’s rings resemble the spectra of water hoarfrost. However, in other parts of the spectrum, a feature that was not characteristic of pure ice was later discovered. In addition to the rings, Saturn has 10 satellites. These are Mimas, Enceladus, Tethys, Dion, Rhea, Titan, Hyperion, Iapetus, Phoebe, Janus. The latter, the closest to Saturn, moves so close to the surface of the planet that it was discovered only by eclipsing the rings of Saturn, which together with the planet create a bright halo in the field of view of the telescope. Saturn’s largest satellite, Titan, is one of the largest moons in the solar system in size and mass. Its diameter is approximately the same as the diameter of Ganymede. Titanium is surrounded by an atmosphere of methane and hydrogen. Opaque clouds move in it. All satellites of Saturn, except for Phoebe, turn in the forward direction. Phoebe orbits with a rather large eccentricity in the opposite direction.