One of the more annoying things about solar systems is planets and other objects don’t stay in one place or even in one orbit. Over time, gravitational interactions can radically change positions and collisions. Well, they can change everything. 

We’d love to understand the history of our solar system, but the only way to do this is to measure where things are now and how they are moving and to then work backward and try and figure out what happened. A good model will explain details like the Great Heavy Bombardment, when asteroids careened into every solid surface we can see. It will also explain how Uranus and Neptune ended up so far from the sun.

As computers get better, scientists can include more and more details in their models, better-approximating reality. In new models published by Matt Clement and collaborators, they ran 6000 simulations of our solar system’s evolution and realized the relationship between Saturn and Jupiter likely wasn’t what we thought it was.

Prior work indicated clearly that these two worlds were once in resonance, with the two planets orbiting so that they lined up over and over with the sun in the same place. It was thought this was a three to two resonance, with Jupiter orbiting three times for every two orbits of Saturn. These new models, however, indicate that it was more likely a two to one resonance, with two Jupiter orbits for every one Saturn orbit. They also found that the positions of Uranus and Neptune were influenced by how much material was in the outer solar system’s Kuiper Belt. This complex interplay of the Kuiper Belt’s gravity and Saturn and Jupiter’s resonance also seems to have kicked out an ice giant from our solar system. This is very much a science of shadows situation, where researchers find missing objects by the shadow they leave in the solar system’s current makeup.

More Information

Carnegie Institution for Science press release