by vox_mundi » Tue 31 May 2016, 16:01:19
Was Planet Nine Captured By The Sun During The Cluster Phase?$this->bbcode_second_pass_quote('', '[')img]https://images.sciencedaily.com/2016/05/160531082201_1_540x360.jpg[/img]
Video Through a computer-simulated study, astronomers at Lund University in Sweden show that it is highly likely that the so-called Planet 9 is an exoplanet. This would make it the first exoplanet to be discovered inside our own solar system. The theory is that our sun, in its youth some 4.5 billion years ago, stole Planet 9 from its original star.
An extrasolar planet, or exoplanet, is by definition a planet located outside our solar system. Now it appears that this definition is no longer viable. According to astronomers in Lund, there is a lot to indicate that Planet 9 was captured by the young sun and has been a part of our solar system completely undetected ever since.
"It is almost ironic that while astronomers often find exoplanets hundreds of light years away in other solar systems, there's probably one hiding in our own backyard", says Alexander Mustill, astronomer at Lund University.
Stars are born in clusters and often pass by one another. It is during these encounters that a star can "steal" one or more planets in orbit around another star. This is probably what happened when our own sun captured Planet 9.
In a computer-simulated model, Alexander together with astronomers in Lund and Bordeaux has shown that Planet 9 was probably captured by the sun when coming in close contact while orbiting another star.
Simulations show that the glancing flyby shown here in a computer image best explains the current structure of our outer solar system. As the star and sun drew nearer, gravity began to take hold of objects in both systems. As the sun and passing star approach each other, gravity can yank small objects from one solar system to the other. Once the stellar encounter is complete, the disk of each solar system contains a mixture of indigenous and captured dust and planets, as shown in the final computer image. Credit: University of Utah and Smithsonian Astrophysical Observatory"Planet 9 may very well have been 'shoved' by other planets, and when it ended up in an orbit that was too wide around its own star, our sun may have taken the opportunity to steal and capture Planet 9 from its original star. When the sun later departed from the stellar cluster in which it was born, Planet 9 was stuck in an orbit around the sun", says Alexander Mustill.
"There is still no image of Planet 9, not even a point of light. We don't know if it is made up of rock, ice, or gas. All we know is that its mass is probably around ten times the mass of earth."
It requires a lot more research before it can be ascertained that Planet 9 is the first exoplanet in our solar system. If the theory is correct, Alexander Mustill believes that the study of space and the understanding of the sun and the Earth will take a giant leap forward.
"This is the only exoplanet that we, realistically, would be able to reach using a space probe", he says.
Alexander J. Mustill et al.
Is there an exoplanet in the Solar system?, Monthly Notices of the Royal Astronomical Society: Letters (2016).
Two planets beyond Pluto?Some Stars Capture Rogue PlanetsGrand Theft Sedna: how the sun might have stolen a mini-planet$this->bbcode_second_pass_quote('', 'O')ver four billion years ago, our sun stole hundreds of frozen mini-planets from a passing star – and the peculiar planetoid Sedna is one of them.
With its extremely elongated orbit taking it 200 times further from the sun than Neptune every 11,400 years, Sedna has been a mystery ever since its discovery in 2003. Its nearest neighbours, the thousand-plus “ice dwarfs” that populate the Kuiper belt beyond Neptune, are believed to be the frozen remnants of our solar system’s formation.
But Sedna, and a dozen other objects with similarly wonky orbits, are harder to explain. A gravitational kick from a planet in our solar system could never have thrown them into such orbits.
One idea was that Sedna could have been jolted out of place by a passing star, but there was little evidence to back it up.
... Using a low-cost, custom-built supercomputer, the team simulated over 10,000 possible encounters to find out which combination of a star’s mass, fly-by distance and velocity would lead to ice dwarfs being gravitationally captured into Sedna-like orbits.
They conclude that the passing star would have been 80 per cent more massive than the sun, and that it came as close as 34 billion kilometres – 51 times Neptune’s distance. The encounter probably took place when the sun was very young and still a member of a newly born star cluster.
The passing star would itself have stolen hundreds of ice dwarfs from the sun’s Kuiper belt, and flung hundreds more into interstellar space.
Scott Kenyon of the Harvard-Smithsonian Center for Astrophysics in Cambridge, Massachusetts, who together with Ben Bromley of the University of Utah in Salt Lake City was one of the first to propose the idea, says the simulations are “pretty convincing”.
