Studies of planetary system dynamics affirm the fine-tuning demonstrated in the solar system, which, in turn, points to supernatural design. Scientists believe that planets around binary stars (two-star systems that are common in the universe) tend to get ejected from the host star, but some simulations have produced stable planetary orbits in such systems. More detailed investigations have shown that the additional star contributes resonances to the system, meaning that the planet experiences repeated gravitational tugs that eventually destabilize its orbit. If the companion star is larger or has a higher eccentricity, the region of stable planetary orbits shrinks to small distances from the main star. Thus, binary stars virtually preclude planetary systems with both rocky and gas giant planets (which protect inner, rocky planets like Earth from asteroidal and cometary bombardment). These simulations further illuminate the fine-tuning required to form a planetary system capable of sustaining long-standing life.