There are a variety of planets differ in size, composition, weight, so we can not speak about a single method for the formation of planets.The unique characteristics of each star system are associated with the peculiarities of its formation.
There are two main theories about the origin of the planets.The first involves the formation in the protoplanetary cloud mass centers around which begins to gather dust and gases from the cloud.This theory is called the theory of accretion and is currently accepted.Another theory - gravitational instability - suggests that planets are formed by the sudden collapse of unstable parts of the protoplanetary cloud.This theory has som
e serious shortcomings.
Around each new stars form a huge cloud of gas and dust, which, under the influence of gravitational forces faster starts to rotate around the star and contract.
After about 1 million years after the star gas-dust cloud is divided into two parts, one closer to the star, the accumulated heavier particles, in another, more distant, mainly situated gas.In the solar system, these areas are divided between the orbits of Mars and Jupiter, that is in the same area formed solid planets, and the other - the gas giants.
in gas-dust cloud as a result of accretion, that is falling and trapping small particles into larger, there is a lot of planetesimals, small objects, which attract more and more substance.The more they get, the faster starts to grow their weight.Sometimes they collide and form even more massive objects.Within a few million years the star there are active processes of violent clashes, the destruction and the formation of planetesimals that are fighting for the remaining material in the cloud.The result is a planetary embryos.
On stabilization process affects the appearance of large gas giants, which are beginning to affect their attraction to smaller embryos to stabilize their orbit.Just a few tens of millions of years, the system has stabilized, planetary embryos grow and the result is a new stable planetary system.