Three bright planets arc low across the evening sky. Venus, the “evening star,” is in the west as night falls, with slightly fainter Jupiter to its upper left. At the same time, golden Saturn is in the southeast. Jupiter and Saturn are the largest planets in the solar system. When they were young, their combined gravity cleared out most of the leftover “building blocks” from the birth of the planets. In fact, a recent study says that process may have cleared the way for the birth of our own Earth. In the solar system’s early years, Jupiter and Saturn danced a complicated ballet. They moved in toward the Sun, then back out again. Their gravity swept away most of the remaining chunks of rock and ice that stuck together to form planets. While most of those bodies were hurled away from the Sun, two researchers from California say that many others were hurled toward the Sun. That created a continuous cannon fire that blasted the planets close to the Sun — worlds that were bigger and heavier
