Photo: Uranus, Neptune Swapped Spots, New Model Says

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The gas giant planets of our solar system took shape twice as close to the sun as they are now and slowly moved outward, according to a new theory that challenges established ideas for how the gas giants formed.

But for this theory to work, the lead author says, Uranus (left) and Neptune (right) had to have switched orbital positions up to four billion years ago.

Uranus image courtesy NASA/Space Telescope Science Institute; Neptune image courtesy NASA/JPL

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