For almost a decade, astronomers have tried to explain why so many pairs of planets outside our solar system have an odd configuration—their orbits seem to have been pushed apart by a powerful unknown mechanism. Yale researchers say they've found a possible answer, and it implies that the planets' poles are majorly tilted. NASA's Kepler mission revealed that about 30% of stars similar to our Sun harbor "Super-Earths." Their sizes are somewhere between that of Earth and Neptune; they have nearly circular and coplanar orbits; and it takes them fewer than 100 days to go around their star. Yet curiously,...