It is possible that such a phenomenon could occur when matter around a newborn star forms into planets. In a planet's orbit around a star, there are two places where a third body can safely orbit. These spots, known as Lagrange points, are 120 degrees in front of and behind whichever body is smaller. The discovered co-orbiting planets, located in the four-planet system KOI-730, are always 120 degrees apart, permanent fixtures in each others' night skies. Fifty million years after the birth of our solar system, the moon may have formed from the debris of a collision between Earth and...