The giant Jovian world, fifth planet from the sun, dominates all the worlds of our solar system. According to astronomers, Jupiter also acts like a massive vacuum cleaner sweeping up much of the debris that litters the outer system. Its powerful gravitational field protects the inner planets from many potential cometary and asteroid collisions.
Billions of years ago, it also saved the Earth and Mars and in the process booted a fifth gas giant—a mega-world almost large enough to become a star—out of the system sending it on its way into the cold depths of interstellar space.
That's the fascinating hypothesis of David Nesvorny who, using a special computer program, simulated the early solar system. Nesvorny, from the Southwest Research Institute in San Antonio, Texas, revealed that the odds are extremely low that the solar system could have become what it is today without a fifth giant—despite the widely held belief the system evolved with only four gas giants.
And that giant, unnamed world would have dwarfed Jupiter despite the fact that Jupiter's so large one hundred Earths could ring its equator.
Using the simulator, Nesvorny determined the early solar system only had "a 2.5 per cent chance of reaching its current population and orbital layout with four giants, but was 10 times more likely to have developed to its present state if there was a fifth monster body in the mix." [Source: Mail]
Although the calculations seemed clear enough, Nesvorny wanted to be absolutely sure, especially since the emerging conclusion flew in the face of scientific theory accepted for more than a century. So, he ran about 6,000 simulations repeated over and over with slightly different variables of orbit, speed, distance and mass, the data of the earliest structure of the system as the gases condensed around the sun and fell into what became a solar system.
"The possibility that the solar system had more than four giant planets initially, and ejected some, appears to be conceivable in view of the recent discovery of a large number of free-floating [rogue] planets in interstellar space, indicating the planet ejection process could be a common occurrence, Nesvorny told the Daily Mail. [For more on rogue planets see "Planets: Billions of Jupiters on the Loose in the Milky Way"]
Some astronomers subscribe to the theory that during the formation of the solar system, Jupiter was much closer to the sun in a fast orbit. The orbital telescope, Keppler, and others have detected hundreds of such star systems. If Jupiter had stayed in such an orbit the Earth and probably Mars would never have formed.
Instead, some "mystery force" knocked Jupiter out of its tight orbit around the sun and catapulted it farther away into a much more benign orbit. During that event, a truly monstrous planet—virtually a stillborn star—was destabilized and booted from its outer orbit at terrific speed.
All this likely occurred, according to the simulation, as the planets first formed some 4.5 billion years in the past. According to astronomers, as the gas and dust coalesced, the planets formed about 10 million or so years afterward.
Unstable in their orbits, they were also bombarded by huge swarms of debris. It's thought an early collision between Earth's two moons created the Moon we have now. ["Earth may have had two moons"]
"Giant planet ejected from the solar system," Southwest Research Institute