They believe impacts from these scattered planetesimals can account for large, dark basins on the Moon. But the scattering also sends planetesimals falling towards the Sun, which may explain another persistent mystery, say the researchers. This scattering allows Neptune to double the size of its own orbit, bringing it approximately to the distance it is today. He says that in the model, Jupiter and Saturn hurl Uranus and Neptune outwards like bowling balls into a sea of planetesimals, which scatter like pins. “Basically, everything sits around for 700 million years and then boom – all hell breaks loose,” says Hal Levison, a team member at the Southwest Research Institute in Boulder, Colorado, US. The resonance allows the pair to greatly disturb the orbits of the other planets. This means they begin to march in lockstep with each other, with Jupiter completing two orbits around the Sun for every one of Saturn’s. After 700 million years, Saturn has migrated outward and Jupiter inward to the extent that they reach a “resonance” point. Gravity pulls the two types of object towards each other, so planetesimals begin to “leak” into the giant planet zone and the orbits of the giant planets gradually change. Surrounding them in a ring are several thousand rocky objects called planetesimals, left over from the formation of the planets. In the model, the four planets form in 10 million years within the current orbit of Uranus. The team has published a trio of papers about their findings in Nature.
Now, an international team of researchers has performed computer simulations that reproduce the orbits of the four giant planets – Jupiter, Saturn, Uranus, and Neptune – in exquisite detail. Jupiter, Saturn, and Uranus, for example, travel in slightly eccentric orbits. But some later deviated from these paths through gravitational interactions with their neighbours. Initially, these bodies are thought to have travelled along circular orbits in the plane of the disc. The research traces three seemingly unrelated phenomena – the giant planets’ orbits, craters on the Moon, and the behaviour of certain asteroids – to the motions of the two gas giants nearly four billion years ago.Īstronomers believe objects in the solar system condensed from a rotating disc of gas and dust about 4.6 billion years ago. Jupiter and Saturn form the basis of a “grand unified theory” of the solar system, according to new computer simulations.