It came in like a wrecking ball. Jupiter may have ploughed through the early solar system, driving some of the first planets to a fiery death in the sun – and cleared room for planets like Earth.
Most other systems we've observed so far contain huge rocky "super Earths" that orbit very closely to their host star – even closer than Mercury is to our sun. By contrast, our system has four small rocky planets, Mercury, Venus, Earth and Mars, that all orbit much further from the sun.
New simulations suggest a wandering Jupiter could explain this. Konstantin Batygin at the California Institute of Technology in Pasadena and Greg Laughlin at the University of California, Santa Cruz, showed that Jupiter could have drifted inwards, pulled by gas swirling around the sun, to somewhere around where Mars now sits today.
As it did, it would likely have pulled any nearby objects along for the ride. These would have then smashed into each other and spiralled into the sun.
Later, a push from another massive planet, Saturn, could have taken Jupiter further out again. The debris left over from all this would have formed the small rocky planets we know today.
"The effect we're looking to take care of turns out to be taken care of by some phenomenon that already explains other parts of the system," says Batygin. "All of the pieces are beginning to fall together, which is very satisfying."
Journal reference: PNAS , DOI: 10.1073/pnas.1423252112
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