In the cover image you can see a captivating natural color view of the planet Saturn. This photo was created from images collected shortly after Cassini began its extended Equinox Mission in July 2008.
Saturn was the furthest of the five known planets in ancient times: Mercury, Venus, Mars, Jupiter, Saturn.
Physical characteristics of Saturn
Saturn is a gaseous planet made up of 90% hydrogen, 5% helium and the other 5% of various materials.
Seen from Earth, Saturn appears as a yellowish object, one of the brightest in the night sky.
With highly sensitive telescopes on Earth, pale belts and band structures parallel to the equator can be seen in the fog of Saturn’s gaseous envelope.
When Galileo looked at Saturn through his small eight-magnification telescope in 1610, he observed that it was not a planet like the other known planets; he saw something like two ears sticking out of the planetary sphere.
In 1659, Christian Huygens, already equipped with better telescopes, was able to clearly distinguish the ring system located in the equatorial plane of Saturn and verified that they are inclined 27º with respect to the plane of the planet’s orbit.
The famous astronomer Pierre Laplace (1749-1827) searched in vain for the causes that would explain the shape of Saturn’s rings.
In the year 1874, the young mathematician Sofia Kovalevskaya in one of her three doctoral theses successfully explained why the shape of Saturn’s rings.
Saturn has a specific density lower than that of water: 0.690 gr/cm³.
The volume of the planet is enough to contain 740 times the Earth, but its mass is only 95 times the Earth’s mass, due to the low average relative density.
This artist’s concept depicts the relative sizes of the planets. Jupiter’s diameter is about 11 times that of Earth, whereas Saturn’s diameter is about 9.5 times greater.
Saturn is the planet with the lowest density.
In any case, an astronaut approaching the surface of Saturn would weigh 95 times more there than on Earth; his muscles would not have enough strength to move his body.
The interior of Saturn is a solid core the size of Earth, about 6,000 km in radius.
One of the curious characteristics of Saturn is that it radiates almost twice the energy it receives from the Sun.
This is due to the fact that in its internal nucleus composed of hydrogen, helium and iron, hydrogen fusions take place that is transformed into helium and gives off large amount of energy.
Saturn orbits the Sun at an average distance of 1,418 million kilometers.
In more technical terms, Saturn is said to be located at a distance from the Sun that varies between 9 AU and 10 AU (AU = astronomical unit, which is the distance between the Earth and the Sun, 149 million km) .
The time it takes for Saturn to circle the Sun (the year of Saturn) is 29.5 Earth years, almost three times the period of Jupiter’s translation.
However, Saturn rotates at high speed on its axis: in 10 hours it makes a complete revolution (on Saturn’s day). Earth does it in 24 hours.
It can be said that Saturn is an immense sphere that rotates at high speed on itself, which is why it is a planet visibly flattened at the poles.
Just because it takes Saturn 29.5 years to make a complete revolution around the Sun does not mean that it moves slowly. It does so at the incredible speed of 34,872 km / hour.
This speed of translation is about 28 times greater than the speed of sound in air. The fastest airplanes in the air force do not exceed 4 times the speed of sound.
The most characteristic aspect of Saturn is its bright rings, which are composed of particles with abundant icy water.
The size of each of the particles ranges from microscopic dust particles to rocks a few meters in size.
The first to observe them was Galileo in 1610. With his own small telescope, after many nights of tenacious observation, Galileo saw something like a star with ears. It was what he could distinguish from the rings.
Due to the dense atmosphere of the clouds, Saturn has a very high albedo: 0.6. Albedo is the reflective power of a body that lacks its own light; a perfect reflector would have albedo 1.
In the next image you can see a beautiful view of the rings, obtained from the Cassini-Huygens probe. The Earth is seen to glow in the distance.
The equatorial diameter of Saturn measures 120,536 km. The polar diameter is 108,728 km, almost 12,000 km smaller than the equatorial
Saturn’s period of rotation varies with latitude, as it does not have a solid surface. Its atmosphere rotates with a period of 10 hours 39 minutes in the area closest to the poles; and with a period of 10 hours 14 minutes in the areas near the equator.
In the 40º latitude zone, the rotation period is 10 hours 37 minutes.
Measurements performed by the spacecraft during these maneuvers have provided the best-yet estimates of the ring system’s age.
Clouds in Saturn
The outer layers are made up of an extensive atmosphere of hydrogen and helium.
Saturn’s atmosphere has dark bands and light zones similar to those of Jupiter.
Strong winds travel the surface, in the direction of the parallels and dominated by an intense and wide equatorial current that reaches speeds of over 1,000 km / hour.
The upper clouds are probably made up of ammonia crystals.
It is believed that there is a layer of water clouds that has not been observed yet.
This photograph was uploaded by Science Photo Library on September 24th, 2018.
The Cassini probe has been able to capture several large storms on Saturn.
One of the largest with lightning 10,000 times more powerful than those of any storm on Earth appeared on November 27, 2007, therefore having been active for several months.
This storm appeared in the southern hemisphere of Saturn, in an area known as “storm alley” due to the high frequency with which these phenomena appear there.
Moons of Saturn
More than 40 moons of Saturn have names; but the exact number of them is uncertain as there are a large number of objects that orbit this planet.
Titan is the most important moon of Saturn. It is the only moon in the Solar System with a significant atmosphere, which has an atmosphere rich in methane, similar to that of the early Earth.
Observations made by the Cassini probe show that a region of Saturn’s moon Titan is very similar to the Etosha Salt Flat in Namibia.
Both are lakes are large shallow depressions that are not always full. Lake Ontario is the largest lake in Titan’s southern hemisphere. It is slightly smaller than its namesake, North America’s Lake Ontario, but completely different in many other ways.
From data obtained with the Cassini probe, the moon Enceladus is believed to have a salty ocean under its crust.
Two other moons, fairly well known, are Iapetus and Phoebe. Phoebe is believed to be an asteroid captured by the gravity of Saturn.
These satellites of Saturn are made up of 30% to 40% rock and 60 to 70% ice.
Saturn’s magnetic field is much weaker than Jupiter’s.
Saturn’s magnetosphere consists of a set of radiation belts in which electrons and atomic nuclei are trapped.
The belts extend up to about 2 million kilometers from the center of Saturn, away from the Sun.
Important dates when observing and exploring Saturn
In 1610, Galileo observed the rings of Saturn through his telescope.
In 1655, Titan was discovered by the Dutch astronomer Christian Huygens.
In 1659, Christian Huygens observed the rings of Saturn more clearly and described their true appearance.
One hundred years later, in 1789, William Herschel discovered two moons: Mimas and Enceladus.
In the late 20th Century on September 11, 1979, the North American probe Pioneer 11 approached a distance of 20,000 km from the upper clouds of Saturn.
In 1980, the Voyager-1 probe reached Saturn at a distance of 124,200 km.
On this occasion, he discovered complex structures in the planet’s ring system and obtained data from the atmosphere of Saturn and its largest satellite, Titan, from which it passed within 6,500 km.
In 1982, the Voyager 2 probe approached Saturn.
At the beginning of the 21th Century, in 2004, the Cassini/Huygens probe reached Saturn.
Cassini became the first rover to orbit that distant world and to get close to its rings.