Orbit: 1,429,4, kilometers (9.54 astronomical units) from the sun
Satellite diameter: 12,536 kilometers (equator)
Mass: 5.68e26 kg
. Cronus, the god of agriculture in Greek mythology, is the son of Uranus and Caia and the father of Zeus (Jupiter). Saturn is also the root of Saturday in English. (See Appendix 4).
Saturn was discovered in prehistory. Galileo first observed it through a telescope in 161 and recorded its strange trajectory, but he was also confused by it. The early observation of Saturn is very complicated, because every few years when Saturn is in its orbit, the earth will pass through the plane where Saturn's rings are located. (Low-resolution pictures of Saturn often change completely. ) It was not until 1659 that Huygens correctly deduced the geometry of the halo. Before 1977, Saturn's rings were considered to be the only ones in the solar system. But in 1977, a faint halo was found around Uranus, and soon after that, rings were also found around Jupiter and Neptune.
Pioneer 11 first visited Saturn in 1979, and was visited by Voyager 1 and Voyager 2 in the same year. The Cassini spacecraft now on its way will reach Saturn in 24.
It is also obvious that Saturn is a oblate sphere when observed through a small telescope. The diameter of its equator is about 1% larger than that of its poles (the equator is 12,536 kilometers, and the poles are 18,728 kilometers), which is the result of its rapid rotation and liquid surface. Other gaseous planets are oblate spheres, but they are not so obvious.
Saturn is the loosest planet, and its specific gravity (.7) is smaller than that of water.
Like Jupiter, Saturn is composed of about 75% hydrogen and 25% helium, and a small amount of water, methane, ammonia and some rock-like substances. These compositions are similar to those of the solar nebula when the solar system was formed.
Saturn, like Jupiter, consists of a rock core, a metallic liquid hydrogen layer and a hydrogen molecular layer, and there are also a small amount of various kinds of ice.
Saturn's interior is extremely hot (up to 12, kelvin at the core), and Saturn sends out more energy to the universe than it gets from the sun. Most of the extra energy, like Jupiter, is generated by the Kelvin-Helmholtz principle. But this may not be enough to explain Saturn's luminous ability, and some other functions may also be going on, which may be caused by the "washing" of helium deep inside Saturn.
The obvious bands on Jupiter are much blurred on Saturn, and become wider near the equator. The earth can't see its top clouds clearly, so people didn't begin to study Saturn's atmospheric circulation until the voyager spacecraft accidentally observed it. Saturn, like Jupiter, has a long-period elliptical orbit (the great red spot in the center of the right image) and other general features. In 199, Hubble telescope observed a very large white cloud near Saturn's equator, which did not exist when Voyager arrived; In 1994, another smaller storm was observed. (left)
From the earth, we can see two obvious rings (A and B) and a dim ring (C). The gap between the rings A and B is called "Cassini part". A darker gap in the outer part of the A-ring is called "Encke Gap" (but this is a bit of a misnomer because it may never have been seen by Encke). The pictures sent back by Voyager show four faint rings. Saturn's rings are different from those of other stars. It is very bright. (The albedo of stars is .2-.6)
Although the rings are continuous from the earth, these rings are actually made up of countless tiny objects in their independent orbits. Their size ranges from 1 cm to several meters, and there may be some objects with a diameter of several kilometers.
Saturn's rings are extremely thin. Although they are 25, kilometers or more in diameter, they are only 1.5 kilometers thick at most. Although they have impressive and obvious images, there is very little matter in the halo-if the halo is compressed into an object, it may only be 1 kilometers wide at most.
The particles in the halo may be mainly composed of ice condensed by water, but they may also be rocky particles wrapped in ice.
Voyager confirmed that the confusing radius inhomogeneity does exist in the halo, which is called "spokes", which was first reported by an amateur astronomer (left). Their natural nature brings us a mystery, but it gives us clues to understand Saturn's magnetic field.
Saturn's outermost ring, the F ring, is a complicated structure composed of smaller rings, and some of its "Knots" are obvious. Scientists speculate that these so-called knots may be massive halo substances or some mini moons. These strange fabrics are obvious in the image sent back by voyager 1 (right), but they can't be seen in the image sent back by Voyager 2, probably because the composition of the halo part photographed by Voyager 2 is slightly different from that of the former.
There are complex tidal vibrations between Saturn's satellites and in its halo system: some satellites, so-called "shepherd satellites" (such as Titan XV, Titan XVI and Titan XVII) are obviously important for keeping the halo shape; Titan seems to be responsible for the lack of some substance in Cassini, which is similar to what happened to Kirkwood gaps in the asteroid belt; Titan 18 is in Encke Gap. The whole system is too complicated, and what we have is still very poor.
The origin of Saturn's rings (and other woody planets) is not clear. Although they may have rings since their formation, the ring system is unstable. They may be constantly updated during their progress, or they may be fragments of larger satellites.
like other woody planets, Saturn has a very meaningful magnetic field.
In the endless night sky, Saturn is easily seen by the eyes. Although it may not be as bright as Jupiter, it is easy to be recognized as a planet because it does not "twinkle" like a star. The halo and its satellites can be observed through a small amateur telescope. Mike Harvey's planet searching chart points out the position of Mercury in the sky (and the positions of other planets) at this time, and then Starry Night, a celestial program, makes more and more detailed customization.
Saturnian moons
Saturn has 18 named moons, more than any other planet. There are still some small satellites to be discovered.
among those satellites whose rotation speed is known, except for Titan and Titan, they all rotate synchronously.
There are three pairs of satellites, Enceladus-Rhea, Enceladus-Rhea and Titan-Rhea, which interact gravitationally to maintain the fixed relationship between their orbits. The period of revolution of Enceladus happens to be half of that of Enceladus, which can be said to be in a 1: 2 * * dynamic relationship, and that of Enceladus-Enceladus is also 1: 2; Titan-Titan has a 3:4 relationship.
In addition to the 18 named satellites, at least more than a dozen have been reported and given temporary names.
satellite distance
(km) radius
(km) mass
(kg) Discovery date
Titan 18th 134 1? Showalter 199
Enceladus XV 138 14? Terrile 198
Titan XVI 139 46 2.7e17 Collins 198
Titan XVII 142 46 2.2e17 Collins 198
Titan XI 151 57 5.6e17 Walker 198
Titan XI 151 89 2.1. E18 Dollfus 1966
Enceladus 186 196 3.8e19 Herschel 1789
Enceladus 238 26 8.4e19 Herschel 1789
Titan 295 53 7.55e2 Cassini 1684
Enceladus XIII 295 15? Reitsema 198
Enceladus XIV 295 13? Pascu 198
Titan 377 56 1.5e21 Cassini 1684
Titan 12 377 16? Laques 198
Rhea 527 765 2.49e21 Cassini 1672
Titan 1222 2575 1.35e23 Huygens 1655
Titan 1481 143 1.77E19Bode 1848
Titan 3561 17 1.88e21. 1671
Titan 12952 11 4.E18 Pickering 1898
Saturn's halo
halo distance
(km) width
(km) mass
(kg)
D 67 75?
c745 175 1.1e18
b92 255 2.8e 19
Cassini part
a1222 146 6.2e18
f1421 5?
G 1658 8 1e7?
E 18 3 ?
(Distance refers to the distance from Saturn's center to the edge inside the halo) This classification is really misleading, because the density of particles changes in a complicated way and cannot be divided into an obvious area by classification: there is constant change in the halo; Those gaps are not all empty, and these rings are not a perfect ring.