<p>Scientists have found that there is low probability of the existence of the mysterious 'Planet Nine', a Neptune-mass world that may circle our Sun at a distance of about 64 billion to 225 billion kilometres.<br /><br /></p>.<p>Earlier this year scientists presented evidence for Planet Nine, leaving theorists puzzled over how this planet could end up in such a distant orbit.<br /><br />"The evidence points to Planet Nine existing, but we can't explain for certain how it was produced," said lead author Gongjie Li, Harvard-Smithsonian Centre for Astrophysics (CfA).<br /><br />Planet Nine circles our Sun at a distance of about 64 billion to 225 billion km, or 400-1,500 astronomical units.<br /><br />This places it far beyond all the other planets in our solar system.<br />Researchers conducted millions of computer simulations in order to consider three possibilities. The first and most likely involves a passing star that tugs Planet Nine outward.<br /><br />Such an interaction would not only nudge the planet into a wider orbit but also make that orbit more elliptical.<br /><br />Since the Sun formed in a star cluster with several thousand neighbours, such stellar encounters were more common in the early history of our solar system.<br />However, an interloping star is more likely to pull the planet away completely and eject it from the solar system.<br />Researchers find only a 10 per cent probability, at best, of Planet Nine landing in its current orbit. The planet would have had to start at an improbably large distance to begin with.<br />Using computer simulations, researchers studied plausible scenarios for the formation of Planet Nine in a wide orbit.<br /><br />"The simplest solution is for the solar system to make an extra gas giant," said CfA astronomer Scott Kenyon.<br /><br />Researchers propose that Planet Nine formed much closer to Sun and interacted with gas giants like Jupiter and Saturn.<br /><br />A series of gravitational kicks then could have boosted the planet into a larger and more elliptical orbit over time.<br /><br />"Think of it like pushing a kid on a swing. If you give them a shove at the right time, over and over, they'll go higher and higher," said Kenyon.<br /><br />"Then the challenge becomes not shoving the planet so much that you eject it from the solar system," he said.<br /><br />That could be avoided by interactions with the solar system's gaseous disk, he suggests.<br /><br />Researchers also examine the possibility that Planet Nine actually formed at a great distance to begin with.<br /><br />They found that the right combination of initial disk mass and disk lifetime could potentially create Planet Nine in time for it to be nudged by a passing star.<br /><br />Researchers looked at possibilities of Planet Nine being an exoplanet that was captured from a passing star system, or a free-floating planet that was captured when it drifted close by our solar system.<br /><br />However, they conclude that the chances of either scenario are less than 2 per cent.<br /><br />The study was published in the Astrophysical Journal Letters.</p>
<p>Scientists have found that there is low probability of the existence of the mysterious 'Planet Nine', a Neptune-mass world that may circle our Sun at a distance of about 64 billion to 225 billion kilometres.<br /><br /></p>.<p>Earlier this year scientists presented evidence for Planet Nine, leaving theorists puzzled over how this planet could end up in such a distant orbit.<br /><br />"The evidence points to Planet Nine existing, but we can't explain for certain how it was produced," said lead author Gongjie Li, Harvard-Smithsonian Centre for Astrophysics (CfA).<br /><br />Planet Nine circles our Sun at a distance of about 64 billion to 225 billion km, or 400-1,500 astronomical units.<br /><br />This places it far beyond all the other planets in our solar system.<br />Researchers conducted millions of computer simulations in order to consider three possibilities. The first and most likely involves a passing star that tugs Planet Nine outward.<br /><br />Such an interaction would not only nudge the planet into a wider orbit but also make that orbit more elliptical.<br /><br />Since the Sun formed in a star cluster with several thousand neighbours, such stellar encounters were more common in the early history of our solar system.<br />However, an interloping star is more likely to pull the planet away completely and eject it from the solar system.<br />Researchers find only a 10 per cent probability, at best, of Planet Nine landing in its current orbit. The planet would have had to start at an improbably large distance to begin with.<br />Using computer simulations, researchers studied plausible scenarios for the formation of Planet Nine in a wide orbit.<br /><br />"The simplest solution is for the solar system to make an extra gas giant," said CfA astronomer Scott Kenyon.<br /><br />Researchers propose that Planet Nine formed much closer to Sun and interacted with gas giants like Jupiter and Saturn.<br /><br />A series of gravitational kicks then could have boosted the planet into a larger and more elliptical orbit over time.<br /><br />"Think of it like pushing a kid on a swing. If you give them a shove at the right time, over and over, they'll go higher and higher," said Kenyon.<br /><br />"Then the challenge becomes not shoving the planet so much that you eject it from the solar system," he said.<br /><br />That could be avoided by interactions with the solar system's gaseous disk, he suggests.<br /><br />Researchers also examine the possibility that Planet Nine actually formed at a great distance to begin with.<br /><br />They found that the right combination of initial disk mass and disk lifetime could potentially create Planet Nine in time for it to be nudged by a passing star.<br /><br />Researchers looked at possibilities of Planet Nine being an exoplanet that was captured from a passing star system, or a free-floating planet that was captured when it drifted close by our solar system.<br /><br />However, they conclude that the chances of either scenario are less than 2 per cent.<br /><br />The study was published in the Astrophysical Journal Letters.</p>