Since 2011, astrophysicists studying the formation of the solar system have suspected that there might have been a fifth gas giant planet four billion years ago that was ejected by the gravitational influence of either Jupiter or Saturn. A new University of Toronto study published in The Astrophysical Journal supports this theory and identifies Jupiter as the bully of the bunch.
"Our evidence points to Jupiter," said Ryan Cloutier, lead author of a new study and a PhD candidate in the University of Toronto's department of astronomy and astrophysics.
If an unfortunate planet was on the losing side of a close encounter with Jupiter or Saturn that slung it out of its original orbit around the sun, then the resulting gravitational influence on other small bodies, such as moons, should have left behind clues still visible today. Cloutier and his colleagues at the University of Toronto created computer simulations of the orbits of Jupiter's moon Callisto and Saturn's moon Iapetus, then calculated the likelihood that each moon would follow its current trajectory in the event that its parent planet expelled a hypothetical planet some four billion years ago.
"Ultimately, we found that Jupiter is capable of ejecting the fifth giant planet while retaining a moon with the orbit of Callisto," said Cloutier. "On the other hand, it would have been very difficult for Saturn to do so because Iapetus would have been excessively unsettled, resulting in an orbit that is difficult to reconcile with its current trajectory."
It wouldn't have been the first time Jupiter terrorized would-be members of our solar system, as it likely absorbed the material that would have formed large terrestrial planets as well. Apparently the giant brute won't be satisfied until it has the sun all to itself.