In what could well have been the galactic equivalent of an Old West style showdown, Jupiter may have metaphorically told another planet that the Solar System wasn’t “big enough for the both of us” and forcibly ejected that world from our region of the Milky Way.
In new research published in the November 1 issue of The Astrophysical Journal, Ryan Cloutier, a Ph. D. candidate at the University of Toronto’s Department of Astronomy & Astrophysics and his colleagues built upon previous research suggesting that there was a fifth gas planet when the solar system originally formed, and tried to explain what happened to that world.
For many years, scientists had suspected either Jupiter or Saturn was to blame, and in the new study, Cloutier’s team discovered evidence that a close encounter with Jupiter was what caused the gas planet to be ejected from the Solar System about four billion years ago.
Evidence supporting the accusations comes from Callisto
The researchers explained that these types of ejections occur when two planets come too close to one another, and one of them accelerates so much that it breaks free from the gravitational pull of the sun. Previous research into these encounters did not account for the effect they might have on other, smaller objects, such as the moons of the giant planets and their orbits.
Cloutier’s team turned their attention on those moons and orbits, using the current trajectories of Jupiter’s moon Callisto and Saturn’s moon Lapetus as the basis for computer simulations. Those simulations were then used to measure the chances that either orbit would have been produced if the respective host planets were responsible for ejecting the hypothetical fifth gas planet, as such an occurrence would have had a drastic impact on the original orbit of either moon.
“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.”
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