Our solar system may have once had a fifth giant planet that was unceremoniously ejected by Jupiter, say Canadian researchers.
A new study published in Astrophysical Journal, called “Could Jupiter or Saturn have ejected a fifth giant planet?” suggests that it was Jupiter, and not Saturn as was previously suspected, that led to the ejection of a fifth ice giant mass planet.
“Our evidence points to Jupiter,” said Ryan Cloutier, a PhD candidate in University of Toronto’s department of astronomy and astrophysics and the study’s lead author.
Since 2006, when Pluto was reclassified as a “Dwarf Planet” because it does not clear the neighborhood around its orbit, the Solar System has been comprised of eight planets. The four smaller inner planets; Mercury, Venus, Earth and Mars, are terrestrial. The four outer planets are “giant” planets. The two largest of the latter, Jupiter and Saturn, are gas giants, being composed mainly of hydrogen and helium. The two outermost planets, Uranus and Neptune, are ice giants.
Since 2011, scientists have suspected that a fifth giant planet was ejected by a gas giant during the early solar system’s proposed instability phase. The new research looked the orbits of planetary satellites Callisto (Jupiter) and Iapetus (Saturn) and determined that the culprit was more likely Jupiter because, based on computer simulations, the violent event would have permanently altered Saturn’s path of orbit.
“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.”
The fifth planet from the sun and the first to form, Jupiter has been explored by robotic spacecraft in the past, and will be visited next year by the NASA New Frontiers mission craft, Juno, which launched in 2011 on a 1.7-billion mile journey. Among other things, the solar-powered Juno will try to determine if Jupiter has a rocky core, whether it has water and oxygen, and will also examine the planet’s infamous winds, which max out at nearly twice the speed of a Category Five hurricane.
Researchers are expecting that when Juno arrives next summer it will give us an unprecedented look at Jupiter, in part because it is getting much closer to the planet than we have ever been before.
“We look deeper. We go much closer. We’re going over the poles. So we’re doing a lot of new things that have never been done, and we’re going to get all this brand-new information,” said, Dr. Scott Bolton, Juno’s principal investigator.
But Bolton says the the ultimate purpose of the mission is much broader in intellectual scope than mere fact checking. he says the mission will look at “…how Jupiter formed. How it evolved. What really happened early in the solar system that eventually led to all of us.”