The dynamical influence of binary companions is expected to profoundly influence planetary systems .
However , the difficulty of identifying planets in binary systems has left the magnitude of this effect uncertain ; despite numerous theoretical hurdles to their formation and survival , at least some binary systems clearly host planets .
We present high-resolution imaging of 382 Kepler Objects of Interest ( KOIs ) obtained using adaptive-optics imaging and nonredundant aperture-mask interferometry ( NRM ) on the Keck-II telescope .
Among the full sample of 506 candidate binary companions to KOIs , we super-resolve some binary systems to projected separations of < 5 AU , showing that planets might form in these dynamically active environments .
However , the full distribution of projected separations for our planet-host sample more broadly reveals a deep paucity of binary companions at solar-system scales .
For a field binary population , we should have found 58 binary companions with projected separation \rho < 50 AU and mass ratio q > 0.4 ; we instead only found 23 companions ( a 4.6 \sigma deficit ) , many of which must be wider pairs that are only close in projection .
When the binary population is parametrized with a semimajor axis cutoff a _ { cut } and a suppression factor inside that cutoff S _ { bin } , we find with correlated uncertainties that inside a _ { cut } = 47 ^ { +59 } _ { -23 } AU , the planet occurrence rate in binary systems is only S _ { bin } = 0.34 ^ { +0.14 } _ { -0.15 } times that of wider binaries or single stars .
Our results demonstrate that a fifth of all solar-type stars in the Milky Way are disallowed from hosting planetary systems due to the influence of a binary companion .