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Jupiter kicked a giant planet out of the solar system 4 billion years ago

3 November 2015 Astronomy Now

The existence of a fifth giant gas planet at the time of the solar system’s formation — in addition to Jupiter, Saturn, Uranus and Neptune that we know of today — was first proposed in 2011. Now astrophysicists at the University of Toronto have found that a close encounter with Jupiter about four billion years ago may have resulted in the fifth giant planet’s ejection from the solar system altogether.