A newly released NASA report suggests that small planets are formed in a wider range of conditions than previously believed. While earlier assumptions held that Earth-like planets were formed primarily around stars with high metal content, a research team led by Lars A. Buchhave has demonstrated that these planets can occur in other star systems too.
Bucchave’s team looked at over 150 stars, using data collected both on the ground and from NASA’s Kepler probe, to determine how the star’s composition impacted planet formation. Says Bucchave:
I wanted to investigate whether small planets needed a special environment in order to form, like the giant gas planets, which we know preferentially develop in environments with a high content of heavy elements. This study shows that small planets do not discriminate and form around stars with a wide range of heavy metal content, including stars with only 25 percent of the sun’s metallicity.
A star’s metallicity is its concentration of elements other than hydrogen and helium. Planets form from large disks of gas and dust that gather around new stars. The composition of the disks is similar to the composition of the stars themselves, thus making metallicity a point of interest. See below for an artist’s rendering of this planet-forming process.
Where gas giants require stars of high metallicity to form, these new findings suggest that smaller Earth-like planets could be more common throughout the galaxy than previously believed.