Move around the Sun nine major planets in the following order starting from Sun: mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune, Pluto. All these planets revolve around the Sun in one direction, called direct. Orbits of major planets are ellipses that are very close to circles, and the planes of their orbits inclined to the Ecliptic at a small angle. The mass of all the planets together make up only with 0.0013(3) the mass of the Sun. In addition to these major planets, mainly between Mars and Jupiter, is moving a large number of smaller bodies called minor planets, or asteroids. The number of known small planets as a result of new discoveries is constantly growing and currently there are more than 1600.
Planets of the solar system in size sharply divided into two groups. To the first group belong to relatively small planets closest to the Sun: mercury, Venus, Earth, Mars. This group is often referred to as group Land. To the second group belong the large planets of the solar system. Jupiter, Saturn, Uranus and Neptune. This group is called the group of Jupiter. Both groups separated by a belt of minor planets, or asteroids. Lonely is poorly studied, small planet Pluto. Considering other physical characteristics of the planets, we see that mnogimi them of the planet is sharply divided into the same two groups. For example, the average density of the planets of the solar system of the first group is 4.5 g/cm3, the average density of Jupiter-1.21 g/cm3. Judging by density, we can say that the planets of the Earth group are solid. The density of the planets jupitervej the same group, close to the density of the Sun, does not allow this conclusion.
Solar system, planets of the solar system
There’s a pretty simple explanation for the strong differences between the four giant planets and four planets of the terrestrial group. (The outer planet Pluto is an exception from this scheme, it seems, is more like one of the satellites of distant planets). Hydrogen-rich planets are changed relatively little original substance from which formed the Solar system. while the solid planets of the earth group lost most of the light gases that form the basis of this substance. Instead of primary atmosphere captured from the gas-dust cloud from which the Solar system formed, they have a secondary atmosphere, formed after the formation of the planets of the solar system.
Comparing the periods of rotation around the axis, and here we notice a big difference between the two groups. The terrestrial planets make a revolution around the axis of the period, most of the day, i.e. they rotate slowly. Planet same group of Jupiter rotate around its axis much faster, on average, the period of rotation of less than half a day. Massive Jupiter rotates in only 9h 50m; it is clear that its linear velocity at the equator would be much more appropriate speed of rotation of the Earth (28 times). In this regard, the planet Jupiter have a large compression of up to 0.1 of Saturn, and the terrestrial planets are almost perfect spheres. The number of satellites of planets of both groups is also quite different. The entire first group has only three satellites, the Jupiter group has more than 30 satellites, and this number is updated with new discoveries.
When the Sun 4.6 billion years ago began the thermonuclear reaction, the temperatures of the planets, especially the inner significantly increased. Two critical factors that determine the future face of the planet – the size of the proto-planet and its distance from the Sun. The small size of the planet is unable to retain hydrogen and helium, the lightest gases. During the formation of the solar system. the decisive role played can planet to retain hydrogen and helium. Another determining factor was the distance from the Sun, from which also depended on whether the hydrogen and helium to overcome the gravity pull of the planet. The fact is that the closer a planet is to the Sun, the higher it is heated, and the harder it is to hold lighter gases on the surface. The results of the joint action of these factors had a significant influence on the formation of planets and split them into 2 main groups.