Small rocky terrestrial planets can form around stars with virtually any shares astronomical "metals" - elements heavier than hydrogen and helium, which indicates the prevalence of such planets in our Galaxy, say astronomers in an article published in the journal Nature.

"I wanted to check, whether formed planet, only certain types of stars and is there a relationship between the size of the planet and the type of the star around which it revolves" - said the head of group of scientists Lars Bokhove (Lars Buchhave) from the University of Copenhagen.

Bokhove and his colleagues studied the spectra and other characteristics about 150 stars, around which the telescope "Kepler" found 220 small planets with a radius not exceeding four of the earth. It is believed that most of these planets - the so-called "supersell" - have a hard rocky surface and in its physical properties similar to the Earth, mercury, Venus and Mars.

As the researchers note, over the last ten years, several groups of planetary community found an interesting relationship between the existence of large planets, the so-called "hot Jupiter", and metallicity star - fraction of elements heavier than hydrogen and helium. It turned out that such planets exist only at those stars, the earth's crust which contain a lot of astronomical "metals".

The authors examined whether there is a similar dependence for terrestrial planet by studying the chemical composition of stars by their spectrum.

"We found that the likelihood of a small planet in a star system, in contrast to the gas giants, not depended on how rich was the star of heavy elements. Planet radius in four of the Earth can be formed around a very different stars, including bodies with a small share "metals" - continued Buchhave.

As the scientists explain, this means that terrestrial planets must meet in our Galaxy far more common than previously thought. Thus, the chances of detecting "double" Land significantly increase.

As a rule, stars with low metal emerged and existed in the youth" Universe, when the elements heavier than hydrogen and helium are rare. Opening Bokhove and his colleagues suggests that the planet earth, and then life, could appear in our Galaxy far sooner than it did on Earth.

The space telescope "Kepler" was launched into orbit in March 2009. It is designed to search for planets "transit method" - by measuring fluctuations in the brightness of stars with the passage of the planet on its disk. Within the primary mission of the telescope will study more than 150 thousand stars in the area of the night sky at the junction of the constellations Cygnus and Lyra. To date, scientists with the help of this tool has detected more than 2.3 thousands of planets candidates.