The solar system is a system of «stars — planets». In our galaxy there are approximately 200 billion stars, among which, as experts believe, some stars have planets. The solar system consists of the central body, the sun and nine planets with their satellites (more than 60 satellites are known). The diameter of the solar system is more than 11.7 billion km.
At the beginning of the twenty-first century. In the solar system, an object was discovered that astronomers called Sedna (the name of the Eskimo goddess of the ocean). Sedna has a diameter of 2000 km. Its one revolution around the Sun is 10,500 Earth years. Some astronomers call this object the planet of the solar system. Other astronomers call planets only space objects that have a central core with a relatively high temperature. Since Sedna is currently located at a distance of about 13 billion km from the center of the solar system, the information about this object is quite scarce.
A special place in the solar system is the Earth — the only planet on which various forms of life develop over billions of years. There are several hypotheses about the origin of the Earth. Almost all of them boil down to the fact that the interstellar dust and gases were the starting material for the formation of the planets of the solar system, including the Earth. However, there is still no clear answer to the questions: how did the full set of chemical elements of the Periodic Table appear in the composition of the planets and what was the impetus for the beginning of gas and dust condensation into the protosolar nebula. Some scientists suggest that the emergence of a variety of chemical elements is associated with an external factor — the explosion of a Supernova in the vicinity of the future Solar System. Apparently, the synthesis of chemical elements occurs as a result of nuclear reactions in the depths and gaseous envelope of the Supernova. A powerful explosion with its shock wave could stimulate the onset of condensation of interstellar matter, from which the Sun and a protoplanetary disk formed, which later disintegrated into separate planets of the inner and outer groups with an asteroid belt between them. This initial stage of the formation of the Solar System is called catastrophic, since the explosion of a Supernova is a natural disaster. On an astronomical time scale, such explosions are not a rare occurrence — they occur on average in a few billion years.
It is assumed that the formation of planets from the protoplasmic disc was preceded by an intermediate phase of the formation of solid and rather large, up to several hundred kilometers in diameter, bodies, called plantizims; their subsequent accumulation and collision caused the accretion (buildup) of the planet, which was accompanied by a change in the gravitational forces.
The radioactive method has established that the age of the most ancient rocks found in the earth’s crust is about 4 billion years. It took billions of years to form our planet — the Earth. The globe, flattened at the poles, orbiting its own axis, moves at an average speed of about 30 km / s in space along an elliptical trajectory around the sun.
Our Earth is amazing and beautiful. Many people represented and represented her. It looks especially beautiful from space, where our compatriot, cosmonaut Yu.A. Gagarin.