Saturn is the sixth planet from the Sun and the second-largest in the Solar System. It is a gas giant predominantly composed of hydrogen and helium. The planet is flattened at the poles and bulges at its equator. The equatorial and polar radii are 60,268 km (37,450 miles) and 54,364 km (33,780 miles), respectively. The temperature and pressure rise steadily toward the core of Saturn, which, in the deeper layers, cause a transition into a metal. The core diameter is about 25,000 km (15,535 miles) surrounded by a thicker liquid metallic hydrogen layer, followed by a liquid layer of helium-saturated molecular hydrogen that gradually transitions to a gas with increasing altitude. Saturn has a hot interior, reaching 11,700 degree C (21,092 degree F) at its core, and it radiates 2.5 times more energy into space than it receives from the Sun.
The outer atmosphere of Saturn contains 96.3% molecular hydrogen and 3.25% helium by volume. The average distance between Saturn and the Sun is over 1.4 billion kilometres. With an average orbital speed of 9.69 km/s, Saturn makes one revolution around the Sun for about 29.5 Earth years. The rotation period around axis is 10 hr and 39 min. Saturn is known to be visually unique for the system of planetary rings that extend from 6,630 km (4,120 miles) to 120,700 km (75,000 miles) outward from the equator, approximately 20 meters in thickness. They are composed of 93% water ice with traces of impurities and 7% amorphous carbon. The particles that make up the rings range in size from dust up to 10 m. The Saturn ring system is the largest and most visible in the Solar System.
Saturn has at least 150 moons, 53 of which have formal names. Here are seven of the biggest satellites as the first in the list is closest to Saturn.
Mimas is a small satelite with diameter about 400 km (250 miles) and surface area slightly less than the land area of Spain. It is composed mostly of water ice with only a small amount of rock.
Enceladus, the sixth largest moon of Saturn has a diameter of only 504 km (313 miles). It is mostly covered by ice, reflecting almost all the sunlight that strikes it, making its surface temperature at noon reach only −198 degree C (−324 degree F).
Tethys is a mid-sized moon of Saturn about 1,060 km (660 miles) across. Its density around 1, indicating that it is made of water ice with just a small fraction of rock.
Dione is another moon of Saturn with 1122 km (697 miles) in diameter. It is very similar to Rhea.
Rhea is the second largest moon of Saturn and the ninth-largest moon in the Solar System with mean diameter of 1530 km (950 miles). It is an icy body with low density that indicates it is made of about 25% rock and approximately 75% water ice.
Titan is the largest moon of Saturn with mean diameter of 5150 km (3200 miles). It is the only natural satellite known to have a dense atmosphere, mainly nitrogen , and the only object other than Earth where surface liquid has been found. Titan is primarily composed of water ice and rocky material, including lakes of liquid hydrocarbon in the polar regions.
Iapetus, or occasionally Japetus is the third-largest natural satellite of Saturn with a diameter of 1470 km (914 miles). The low density of Iapetus indicates that it is mostly composed of ice, with only a small (about 20%) amount of rocky materials.