How circumbinary planets form revealed

Researchers using Kepler space telescope have discovered how circumbinary planets form.

Kepler-34(AB)b is a circumbinary planet, so-called because its orbit encompasses two stars. There are few environments more extreme than a binary star system in which planet formation can occur. Powerful gravitational perturbations from the two stars on the rocky building blocks of planets lead to destructive collisions that grind down the material.

Dr. Zoe Leinhardt and colleagues from Bristol's School of Physics have completed computer simulations of the early stages of planet formation around the binary stars using a sophisticated model that calculates the effect of gravity and physical collisions on and between one million planetary building blocks.

They found that the majority of these planets must have formed much further away from the central binary stars and then migrated to their current location.

Based on these conclusions for Kepler-34, it seems likely that all of the currently known circumbinary planets have also migrated significantly from their formation locations - with the possible exception of Kepler-47 (AB)c which is further away from the binary stars than any of the other circumbinary planets.

The research has been published in Astrophysical Journal Letters.