About the tilt of Uranus' axis

[bbbl67]

TL;DR Summary

Was Uranus in a tussle with Neptune and Planet 9?

Now, Uranus seems to have had an eventful early life. According to theory, it got hit by a large planetary body, which knocked it's axis to nearly 90°. Also according to another theory, it apparently had a close encounter with Neptune which took Neptune further away, when initially it was closer than Uranus.

I'm wondering if maybe the two events were related, and possibly the same event? I'm also wondering if a third body was involved in this, let's say the hypothetical Planet 9? What if at one point Planet 9 and Uranus got into a very close orbit with each other, such that they were basically a dual-planet system for a little while. Then Neptune tried to come into the mix, and it ended up knocking Planet 9 out into a huge orbit, and ended up skewing Uranus' rotation axis, as Planet 9 went flying off?

 

[MikeeMiracle]

The latest understanding on Uranus 90° was that no single impact could have caused it without having a catastrophic effect on Uranus itself, we now believe it was 2 impacts, both glacing blows that tilted it to its current orientation. I am not sure how having a close encounter with Neptune could have caused it to tilt onto it's side.

I assume you are implying an impact with the proposed Planet 9. I am not sure we can really discuss planet 9 here without falling foul of the forum rules as it's not been proven yet. And speculation that it may have been caused by planet 9 is just that, speculation which I believe also is not allowed without some proof.

 

[bbbl67]

I assume you are implying an impact with the proposed Planet 9. I am not sure we can really discuss planet 9 here without falling foul of the forum rules as it's not been proven yet. And speculation that it may have been caused by planet 9 is just that, speculation which I believe also is not allowed without some proof.

No, I wouldn't say I am talking about an impact with Planet 9, but rather an orbital dance. Let's say an early Uranus and an early P9 got into a close orbit of each other, sort of a dual-planetary system rather than a planet-moon system. Then eventually Neptune closed in onto the dual planet system, and the smallest of the planets, P9, got kicked out to the outer solar system, but not before torquing Ur into its 90° tilt.

 

[MikeeMiracle]

I'm still not convinced by what mechanics it could turn Uranus sideways if it's on the same plane as the rest of the planets, if it could then surely we would see other bodies sideways also. Hopefully someone more familiar with planetary bodies could step in here.

As for being the smallest planet, while it's diameter might be smaller Uranus, it is proposed to be a super earth, a rocky planet 8 times bigger than Earth. If it does exist and turns out to be a rocky planet, while being smaller it might still have a comparable mass to Uranus which is a gas giant.

 

[davenn]

I'm still not convinced by what mechanics it could turn Neptune sideways

You mean Uranus ?? Neptune isn't on its side

 

[MikeeMiracle]

Yes, apologies, corrected now