Jupiter may have bumped a giant planet from the solar system

TORONTO, Oct. 29 (UPI) -- In 2011, astronomers first proposed that our solar system may have once hosted a fifth gas giant. But where did the missing planet go? And how did it get pushed out?

Now, researchers at the University of Toronto suggest it was Jupiter who played the bully.

Scientists had previously surmised that interactions between two giant planets, having drifted too close together, could be powerful enough to throw one out of the grasp of the sun's gravity. Saturn and Jupiter were the most likely candidates.

Unable to convincingly finger one or the other, astrophysicists realized they needed to look at the two gas giants' satellites -- Jupiter's Callisto and Saturn's lapetus. What effects would a jostle between two massive planets have on their moons?

Researchers ran computer simulations to determine which moon's orbit could survive or be explained by a significant planetary kerfuffle.

"Ultimately, we found that Jupiter is capable of ejecting the fifth giant planet while retaining a moon with the orbit of Callisto," Ryan Cloutier, an astrophysicist and doctoral candidate at Toronto, said in a press release. "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."

Computer models are the reason scientists suspect a missing fifth gas giant. Simulations attempting to recreate the planetary evolution in the solar system work better when an early extra planet is included.

If there was a fifth gas giant, scientists aren't sure where it is now, but other rogue planets have been observed in interstellar space.

The new findings are detailed in a paper published online in the Astrophysical Journal.