Why is Uranus on its Side? An Ancient Catastrophe of Planetary Proportions

The Earth’s tilt is nothing compared to Uranus, which has been flipped right over on its side. What could have caused such a devastating impact to the planet to make it this way?

Follow us on Twitter: @universetoday

Team: Fraser Cain - @fcain
Jason Harmer - @jasoncharmer

Created by: Fraser Cain and Jason Harmer
Edited by: Chad Weber
Music: Left Spine Down - “X-Ray”

It’s impossible to do an episode about Uranus without opening up the back door to a spit storm of potty humour. I get it, there’s something just hilarious about talking about your, mine and everyone’s anus. And even if you use the more sanitized and sterile term urine-us, it’s still pretty dirty, in an unwashed New York stairwell kind of way. You’re in us? No.

This is a no-win solution. It’s a Kobayashi Maru scenario here. We’re all doomed.

Can we call a truce? I dare you commentators, to keep the YouTube comments as pure and clean as driven snow, so we can focus on the super interesting science. Think of the children.

Let’s set the stage, I’m going to let planetary astronomer Kevin Grazier give you the proper pronunciation to clear our minds and let us move forward with grace and civility.

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Kevin Grazier:
Strictly speaking, it's pronounced Youranous, is the pronunciation.

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As you probably know, Uranus… I mean Ouranus. No, I can’t do it, my brainwashing is too far along. Save yourselves!. Anyway, Uranus is the 7th planet from the Sun, and the 3rd largest planet in the Solar System. Jupiter and Saturn get all the spacecraft and Hubble space telescopes, but Uranus is an incredibly worthwhile target to visit.

It’s almost exactly 4 times larger than Earth and has its own set of strange dusty rings - perhaps left over from a shattered moon. It has at least 27 moons, that we know of, and many more interesting features that would fascinate astronomers, if we had a spacecraft there, which we don’t. Which is ridiculous. We’ve only made one close flyby of Uranus by Voyager II back in 1986.

We’ve seen Pluto up close, but there are no plans to visit Uranus? Madness.

Anyway, perhaps one of the strangest aspects of Uranus is its tilt. The planet is flipped over on its side, like a Weeble, that wouldn’t unwobble.

Actually, all the planets in the Solar System have some level of axial tilt. The Earth is tilted 23.5 degrees away from the Sun’s equator. Mars is 25 degrees, and even Mercury is 2.1 degrees tilted. These tilts are everywhere.

But Uranus is 97.8 degrees. That’s just 0.2 degrees shy of a 90s boy band.

You might be wondering, why have it be more than 90 degrees. High school geometry tells me that 97.8 degrees is the same as 82.2 degrees. And that’s true. But astronomers define the angle as greater than 90 degrees when you take its direction of rotation into account. When you describe it as turning in the same direction as the rest of the planets in the Solar System, then you have to measure it this way.

What could have done that to Uranus, how could it have happened?

The fact that Uranus is flipped over on its side tells us that the calm clockwork motion of the Solar System hasn’t always been this way. Shortly after the formation of the Sun and planets, our neighborhood was a violent place.

The early planets smashed into each other, pushed one another into new orbits. Some planets could have been spun out of the Solar System entirely, while others might have been driven into the Sun. Our own Moon was likely formed when a Mars-sized object crashed into the Earth. Other moons might have been captured from three body interactions between worlds.

It was mayhem.

The Solar System that you see today contains the survivors. Everything that wasn’t delivered a death blow.

And something really tried to deliver a death blow to Uranus, very early after it formed. We know this because the moons of Uranus orbit at the same tilt as the planet’s axis. This means that something smashed into Uranus while it was still surrounded by the disk of gas and dust that its moons formed from.

When the massive collision happened, the planet flipped over, wrenching this disk with it. The moons formed within this new configuration.

Astronomers think it was more complicated than that, however. If it was a single, massive collision, models suggest the planet would just flip over entirely, and end up rotating backwards from the other planets in the Solar System.

[willman]

So let me get this straight... What you are saying is that a large object smashed Uranus really hard?

[joescott]

I would love to see an animation of what the sun's patterns would be if you stood on the equator of Uranus.

[georgenelson]

" 0.2 degrees shy of a 90's boy band " LMAO Fraser. Got a great laugh 😂😂😂

[oldatarigamer]

So what you are saying is that something kicked Uranus?

[The_NSeven]

"why is uranus on the side?" because you're laying :P

[Robot_Overlord]

if you look close, there is a ring around uranus

[Simon-hbrf]

well looks like the comments section failed that dare lol

[czechultimatestyle]

I love that you always make your vids in front of nature and not in your bedroom like many youtubers does

after seeing many vids, now im subscribing :)

[prohorizon]

I would like to see a video on the planet Urectum!

[jasonemmons]

Uranus is 4X the width of the Earth...

[DrogoBaggins]

00:03 opening the back door... I see what you did there.

[GehennaGirls]

Um, how can something even be said to "collide" with a gas planet?

[BryanEshbaugh]

This is the kind of video I will use to teach a kid someday. Thank you Fraser!

[cortster]

Thinking about the scales of planetary collisions makes me feel so small... I love it. I can't even wrap my head around the amount of energy that would be exchanged during such a collision, even if I have a mathematical idea.

[zachcrawford]

Thanks for clearing up the over 90 degree tilt thing that never made sense to me before.

[poochiecheeks]

this is one of the funniest astronomy videos i've ever seen thank you fraiser

[idksil]

As overwhelming as Jupiter and Saturn were, Uranus and Neptune are indeed still unexplored. I hope mission concepts will be presented in the 2020 decadal survey. 🔭😉🔋🚀

[apophus]

I have a request. I would love to see a video demonstrating where a Goldilocks zone would be in caparison to different types of stars? For example we know the goldilocks zone of our solar system. but where would a planet have to be say in a white dwarf system or a binary system, or a red super giant system to support life?? Hope that makes sense.

[wildman]

As suggested by Fraser Cain, I'm posting up a request to see more about Uranus's neighbor, Neptune. Its such a major player in the development and constitution of the outer solar system and it gets little research and even less press in the astronomical news. Its a totally underrated planet I would love to hear more about!

[daffidavit]

When I was in Grammar school in the late 1950's everyone called the planet (ur anus). Really, then in the 1960's, after Star Trek TOS came out, the Klingons around Uranus jokes began. Then Carl Sagan started calling it (ur ran us) and the new name stuck. This is true history as I recall it.