Historically, humans have often felt the need to be special, and just as often have been disappointed. The Earth, as it turned out, wasn't at the center of the universe. Humans are smart, but in the end, they evolve, live and die just like all the other living things on the planet. In astronomy, the prevailing theoretical models of how the solar system got here have assume that, based on past experience, we're probably just an average solar system.
But according to a new study by Northwestern University astronomers looking at 300 planets orbiting other stars, we might really be special. "We now know that these other planetary systems don't look like [our] solar system at all," said Frederic Rasio, an astronomer at Northwestern, in Chicago. Computer simulations used by Rasio's team showed that the birth of a planetary system is a very violent affair, with the gas disk that gives birth to the planets pushing them toward the central star, where they often crowd together to be engulfed. Gravitational encounters between growing planets fling some across the planetary system, or into deep space. "Such a turbulent history would seem to leave little room for the sedate solar system, and our simulations show exactly that," said Rasio in a news release from Northwestern University. Our solar system "had to be born under just the right conditions to become the quiet place we see," he said. "The vast majority of other planetary systems didn't have these special properties at birth and became something very different."