Jupiter, the largest planet in the solar system, leads the Moon across the sky tonight. They rise in late evening, with brilliant Jupiter well to the Moon's upper right.
Jupiter is five times farther from the Sun than Earth is. But that hasn't always been the case. In fact, it's possible that it moved in and out a good bit during the solar system's early days -- a scenario described as "jumping Jupiter."
Jupiter and the solar system's other giant planets probably formed before Earth and the other inner planets.
Some simulations show that Jupiter could have moved as close to the Sun as Mars is today. If so, it swept up a lot of the planetary "building blocks" in that region. So when it began to move away from the Sun, there wasn't much left, which is why Mars is only half as big as Earth.
Over several hundred million years, Jupiter, Saturn, Uranus, and Neptune all moved farther from the Sun as they kicked around the leftover planetary building blocks.
When those smaller bodies were gone, the giants got involved in a gravitational wrestling match. One study says that Saturn pushed either Neptune or Uranus in toward the Sun, which pushed Saturn itself away from the Sun.
As the smaller world approached Jupiter's domain, though, Jupiter gave it a big kick outward, which in turn pushed Jupiter inward. That was the last "jump" for Jupiter, as it and the other giant planets quickly settled into orbits that are much like the ones they follow today.
Script by Damond Benningfield, Copyright 2011