New research has shown that billions of stars in our galaxy captured stray planet that once roamed in interstellar space. These nomadic worlds, which were kicked out of their home star systems, found a new home with another star. This finding may explain not only the existence of the planets, which orbit at a surprisingly far from their stars, but also the existence of double planets.
"The stars are not exchanged between planets smaller than sports clubs exchange players," - said Hagai Peretz of the Harvard-Smithsonian Center for Astrophysics.
The study will be published April 20 in the Journal of The Astrophysical Journal.
The researchers came to these conclusions by creating a model of the star cluster containing the free world. They found that if the number of stray planets equal to the number of stars, then 3 to 6 percent of the stars eventually captured the free planet. The more massive the star, the higher the probability of capture passing nearby planet.
They studied young clusters of stars, because the closer to each other and the stars are free of the planet, the greater the likelihood of such a capture. As clusters expand with time, the meeting with the stars of the planets should occur at an early stage of development of the cluster.
The occurrence of stray planets is a natural consequence of the processes occurring during the formation of stars. The newborn star system often contains several planets. During the interaction between the two planets, one of which can be thrown out into interstellar space. In the event that on the way of the following she would meet another star moving in the same direction and with the same speed, it can join the passing star.
Such planets are captured, usually at a distance of hundreds or thousands of times farther from the star than the Earth is from the Sun. Also, the orbit of this "adoption" of the planet may be at an angle to the orbits of the planets and relatives can rotate around the star in the opposite direction.
Astronomers have not been able to find candidates for the title of undisputed captured planets, due to the high probability of detection of intruders. The fact that the gravitational interaction within the planetary system can throw the planet into a wide, inclined orbit, which by all accounts will be like a trapped orbit of the planet.
The main signs that indicate the capture, would be the discovery planet orbiting at a large distance from the star of low mass, as the stellar disk of material would not be enough for the formation of the planet at such a distance.