Out of more than 4,500 known planet-hosting stars, one surprising pattern stands out. While planets are expected to form around most stars and many stars exist in pairs, worlds that orbit both stars are unusually uncommon. Among the more than 6,000 confirmed extrasolar planets, or exoplanets, discovered so far -- most by NASA's Kepler Space Telescope and the Transiting Exoplanet Survey Satellite (TESS) -- only 14 have been seen orbiting binary stars. Based on expectations, astronomers thought there should be hundreds. So where are the real-life versions of Star Wars' Tatooine? Researchers at the University of California, Berkeley, and the American University of Beirut now suggest an answer, and it points to Einstein's general theory of relativity. How Gravity Shapes Orbits in Binary Star Systems In a typical binary system, two stars with slightly different masses circle each other along elongated, or elliptical, paths.…