In the Solar system's four gas giants (Jupiter, Saturn, Uranus and Neptune), which, according to scientists, there used to be much closer to the Sun than it is now. David Nesvorny from Southwest research Institute (USA) and Alessandro Morbidelli from the Observatory of the Cote d'azur (France) believe that the giants were more than five or six.

According to the existing so-called model of nice, at the dawn of the Universe gas giants revolved more correct circular orbits, and their distance from the Sun does not exceed 17 astronomical units. Thus far beyond the orbit of these planets were located a big solid disc, made of stone and ice planetesimals, stretching at a distance of 35 astronomical units from the Sun - that is beyond the current orbit of Neptune.

Planetesimals on the inner edge of the disk periodically entered into gravitational interaction with the remote of the giants, which changed their orbits and carrying away closer to the Sun. This was accompanied by the exchange of planets and small icy bodies pulses. To offset the transferred momentum planet giant slightly shifted from the Sun, starting more frequently "push" planetesimals to the sun.

Thus, the orbit of Uranus, Neptune and Saturn consistently moved until planetesimals did not come close to Jupiter. After a few hundred million years of Jupiter and Saturn entered the orbital resonance 1:2 or 2:3), which led to a sharp increase in the eccentricity of their orbits and destabilized the entire system. Under the influence of Jupiter Saturn began to move away from the Sun, along the way, pushing out from there also Neptune and Uranus.

Although this model explains many things, including the late heavy bombardment our system attempts to simulate these processes on the computer while it was not possible: one of the four giants is ejected from the system, earth-planets start to collide with each other, or the orbit of Jupiter is incorrect, leading to destabilization of the orbits of the other phone

Nesvorny, Morbidelli suggested that the model is correct, just the giant planets, which had the strongest influence on the formation of the Solar system in its present form, was more than four. In this case, the presence of the fifth giant would be able to protect the planet earth from frequent collisions between themselves and at the same time to stabilize the system during migration giants to the outer orbits. But eventually "extra" giant was thrown out by the gravity of Jupiter from the Solar system.

There was also analyzed the model with the participation of the sixth giant. But the probability of evolution of such a system that, as we now see, was slightly smaller than in the case of the five giants, though higher than in a system where initially there were only four giant.

What was this hypothetical "fifth element"? The researchers believe that the mass and density it was something in-between Neptune and Uranus. If you still giants was six, their mass should be half of the mass of Neptune (8-9 earth), that allows to carry them to the class of "supersell". By the way, this easily explains the lack of planets of this class in the Solar system, although generally in our Galaxy they are pretty common.

Immediately raises another question is how this model, involving the expulsion of the system's giant planets may be common in the Universe? Interestingly, while scientists never managed to find such interaction between the earth-planets, asteroids, as well as gas and ice giants. Moreover, already known cases when the giant planets are closer to the star than earth planet.

After spending about 10 thousand simulations of the development of stellar systems from its original state, astronomers have come to the conclusion that this development could proceed in many variations, suggesting a different distribution of planetary orbits, which does not coincide with the present. The probability of education system similar to our own, is about 5 percent, that is, only every twentieth star system may have a similar structure. However, current data on the number of planetary systems indicate that only within the milky Way must be at least a few billion of our "doubles".