Jupiter may have determined number of planets in solar system

Los Angeles Times : Our inner solar system is unusual in that it has far fewer planets than most other planetary systems discovered so far. Why it is not crowded with so-called super-Earths, planets with masses exceeding those of Earth, may be due to Jupiter, whose early orbit of 3–10 astronomical units from the Sun varied wildly before settling in to its current one of 5–5.5 AU. A group of researchers has proposed that in the early solar system, a young Jupiter may have migrated toward the Sun, sweeping along many of the other, smaller objects around it. In the process, those objects may then have collided with each other, broken up into dust, and drifted along into the Sun. As Jupiter reversed course and settled in to its current orbit, the remaining debris formed into the solar system’s terrestrial planets. The discovery of more exoplanetary systems should help determine whether that scenario is likely.