The planet Kepler-34(AB)b, discovered by the Kepler space telescope, is a circumbinary planet, so-called because its orbit encompasses two stars.
A binary star system is possibly the most extreme environment in which a planet could form, researchers at the University of Bristol said, since powerful gravitational perturbations from the two stars on the rocky building blocks of planets should lead to destructive collisions that grind down the material.
So, how can the presence of such planets be explained?
Zoe Leinhardt and colleagues from Bristol's School of Physics, conducting computer simulations of the early stages of planet formation around binary stars, found the majority of these planets must have formed much further away from the central binary stars and then migrated to their current location.
"Our simulations show that the circumbinary disk is a hostile environment even for large, gravitationally strong objects," Leinhardt said. "Taking into account data on collisions as well as the physical growth rate of planets, we found that Kepler 34(AB)b would have struggled to grow where we find it now."
Their results suggest all of the currently known circumbinary planets likely also migrated significantly from their formation locations, the researchers said.
"Circumbinary planets have captured the imagination of many science-fiction writers and film-makers -- our research shows just how remarkable such planets are," lead study author Stefan Lines said. "Understanding more about where they form will assist future exoplanet discovery missions in the hunt for earth-like planets in binary star systems."