Our Sun may have snatched Planet 9 from its native solar system

Nothing is static in the universe, but you don’t think of something as large as a planet immigrating to a new solar system. While comets buzz around with giant, oblong orbits, and even Jupiter may have relocated itself billions of years ago, the Sun’s gravitational pull has helped maintain the original lineup of planets from the birth of the solar system. In fact, the Sun’s gravity may have been strong enough to pick up another planet altogether, kidnapping it from its native solar system.

Unproven planet

The planet in question is currently known as Planet 9, and astronomers still don’t have direct evidence it exists. Hypothesis about it stem from witnessing strange disruptions to the orbits of objects past Pluto in the an area known as the Kuiper belt. Those orbital wobbles were significant and regular enough to suggest something 10 times the mass of Earth is out there, even though we don’t have a good way to see it yet. In the mean time, astronomers have been trying to figure out what it could and couldn’t be, which is strongly influenced by where it came from.

If Planet 9 is a native of our solar system, it’s though to likely be made of materials common to other local planets, like iron and hydrogen. However, the estimated size, plus an orbit ten times as wide as Pluto’s casts some doubt on this scenario, partially because it doesn’t make a lot of sense for that much mass to be gathered that far out away from the Sun. It’s possible it moved from closer in our solar system, but astronomers from Lund University are now suggesting that it moved in from another solar system entirely.

Gravitational grab

Planet 9’s origin would then be as a planet closer to a star that was once much closer to our Sun. Other planets around that star may have then shoved Planet 9 towards the edges of the star’s gravitational influence, where our Sun was able to basically scoop it up into a new orbit. As our Sun and Planet 9’s home system moved apart, it left our Sun as the primary influence on the planet’s orbit, with no influences to pull it away again.

If this proves to be true, it throws open questions of the Planet’s composition, since it would no longer need to be composed of materials similar to other planets formed in our own solar system. If it was pushed out of it’s original home, it may be nicer to think of this as a cosmic adoption, rather than a kidnapping.

My first grader asked: Will Planet 9 be a problem for the laser spaceships? They don’t want to run into it!

The laser-propelled spacecraft planned by Breakthrough Starshot probably won’t have a problem with Planet 9. While we don’t have a great way to look directly at Planet 9 right now, the Large Synoptic Survey Telescope should be receiving data by 2021, over a decade before any possible launch of Starshot laser-saucers. By the time a specific route is being chosen, we should have no trouble avoiding a planet with a 15,000 year orbit.

Source: Is 'Planet 9' a Kidnapped Ex-Exoplanet? by Ian O'Neill, Seeker