New research suggests Jupiter booted another planet out of our solar system four billion years ago.
Scientists believe a fifth gas giant existed in the solar system at the time of formation, the University of Toronto reported. In the past researchers were unsure if the planet actually existed and if Saturn pushed it out, but these new findings suggest Jupiter was the culprit.
"Our evidence points to Jupiter," said Ryan Cloutier, a PhD candidate in U of T's Department of Astronomy & Astrophysics and lead author of a new study published in The Astrophysical Journal.
Planetary ejections usually occur as a result of close encounters between planets in which one of the objects accelerates so dramatically that it breaks free from the strong gravitational pull of the Sun. Past studies have suggested this phenomenon is possible between gas giants, but failed to look at the effect such an event would have on the planets' moons.
To make these new findings the researchers looked closely at moons and orbits. They developed computer simulations that focused on the modern-day trajectories of Callisto and Lapetus, Jupiter and Saturn's moons. Using this new model, the team calculated the likelihood that each secondary object would be able to create its own gravitational orbit if its host planet was ejected from the solar system.
"Ultimately, we found that Jupiter is capable of ejecting the fifth giant planet while retaining a moon with the orbit of Callisto," said Cloutier, who is also a graduate fellow at the Centre for Planetary Sciences at the University of Toronto at Scarborough. "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."
