Space Travel
11, Feb, 2012

Giant Planets Orbits Changed
Written by spacetravel.org   
Wednesday, 01 June 2005 17:45
Jupiter, Saturn, Uranus and Neptune may once have been bunched together, closer to the Sun. Hal Levison and his colleagues at the Southwest Research Institute in Boulder Colorado have used a computer simulation to study the orbits of these giant planets and noted that while planetary formation theories suggest that the giant planets formed circular and coplanar orbits, Jupiter, Saturn and Uranus have orbital eccentricities ranging from 6 to 9 percent. Additionally, the inclinations of the orbital planes of Saturn, Uranus and Neptune take maximum values of approximately 2° with respect to the mean orbital plane of Jupiter. The researchers believe that a planetary system with initial quasi-circular, coplanar orbits could have evolved to the current orbital configuration.

The scientists believe that the system of the four giant planets was once very compact, between 5.5 and 17 astronomical units. At that time, their orbital eccentricities and inclinations were very small. Beyond these planets was an orbiting band of gas, dust and ice. They say that the pull of gravity between these particles and the planets caused them to move further apart, with Jupiter moving closer to the Sun, while Saturn, Uranus and Neptune moved further away.

Once the orbits of Jupiter and Saturn aligned, so that Saturn took twice as long as Jupiter to orbit the Sun, the gravitational pull of the two planets acting together changed Saturn’s orbit slightly. This is in turn affected Uranus and Neptune, whose orbits began to resemble squashed ovals. Uranus and Neptune then began to move through the band of ice, dust and gas, scattering debris throughout the Solar System.

The scientists believe that some of the debris may have become trapped around Jupiter, which could account for the presence of Trojan asteroids both leading and trailing Jupiter. Some of the debris may have been thrown toward the inner planets, creating the huge craters on the Moon and elsewhere.

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