The researchers explored the likelihood that our solar system exchanged solid matter with its closest planetary-system neighbor during the first hundreds of millions of years it existed. At that time, our sun belonged to a tight-knit star cluster filled with other planetary systems. The above simulation shows that two planetary systems (green and blue dots) -- about 3.26 light years apart -- orbit a common center of mass. Over a period of roughly 8.7 million years, various objects (black dots) are pulled in and repelled by the systems' gravity. Displaying weak transfer, one object (red dot) first wanders into the green system's gravity boundary and partially orbits it before being cast off. The red object then drifts before being pulled in by the blue planetary system.