Astronomy

Scientist Jupiter Saved Earth Ejected Gigantic Planet from Early Solar System



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We have much for which we should be grateful to Jupiter, our solar system's immense gas giant. The planet is a magnet for meteorites and asteroids large enough to wipe out all life on Earth, as reported by CBNnews.com after a particularly large impact in 2010. But now astronomers believe it goes further, that Earth might have been saved far back in the history of the Solar System, when Jupiter's early erratic orbit may have ejected a gigantic planet from our neighbourhood, and out into interstellar space.

This hypothesis, reported by Astronomy Now among others, has come about thanks to computer simulations of the Solar System carried out in Texas by the Southwest Research Institute's David Nesvorny. The outer solar system may once have had five rather than four giant planets, and the fifth could have been pushed out towards the Kuiper Belt, the very fringes of the Sun's influence.

We know from observation of the Moon's cratered surface that the ancient Solar System saw some instability, which astronomers attribute to planets 'jumping around' before settling into their new orbits. The sheer gravity of the giant planets in the outer Solar System shook some smaller objects from their orbits and sent them hurtling further in towards the Sun, causing the pock marks on the Moon's ancient surface, among other things.

Nesvorny and other scientists believe that Jupiter may well have migrated inwards in the Solar System, and he raises the possibility that unchecked Jupiter's momentum could have disrupted the orbits of other planets, maybe even causing Earth to collide with nearest neighbours Mars or Venus.

Nesvorny's colleagues suggested that Jupiter's migration was altered by a brush with Neptune or Uranus, but that would have meant one of those two planets being ejected from the Solar System. And so a fifth gigantic planet has been theorised, a body which would have had roughly equivalent mass to Neptune or Uranus, and could have helped Jupiter settle into its current orbit at the cost of a one way ticket to the Kuiper Belt and beyond. This scenario plays out with the established facts in Nesvorny's simulations.

Described like this it seems more as though it was the fifth giant rather than Jupiter that saved Earth on this occasion, taking the astronomical equivalent of a bullet for us. With astronomers now discovering various isolated objects floating in interstellar space, it seems that this kind of solar snooker could be surprisingly common.

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