by Fraser Cain
It’s impossible to do an article 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.
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.
Kevin Grazier:
Strictly speaking, it’s pronounced Youranous, is the pronunciation.
Strictly speaking, it’s pronounced Youranous, is the pronunciation.
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.
Diameter comparison of Uranus and Earth. Approximate scale is 90 km/px. Credit: NASA
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.
It’s more likely that another collision or even a series of
collisions put the brakes on Uranus’ end over end roll, putting it into
its current configuration. It boggles the mind to think about what must
have happened.
Uranus’
tilt drastically affects the amount of sunlight the hemispheres receive
during its orbit. Credit: NASA, ESA, and A. Feild (STScI)
Having such a huge axial tilt makes a big different to Uranus. As it
travels around the Sun in its 84-year orbit, the planet still has its
poles pointed at fixed locations in space. This means that it spends 42
years with its northern hemisphere roughly pointed towards the Sun, and
42 years with its southern hemisphere in sunlight.
If you could stand on the north pole of Uranus, the Sun would be
directly overhead in the middle of summer, and then it would make bigger
and bigger circles until it dipped below the horizon a few decades
later. Then you wouldn’t see it for a few decades until it finally
reappeared again. It would be very very strange.
Of course, it’s a gas planet, so you can’t stand on it. If you could
stand on it, we’d all be marveling at your ability to stand on planets.
Here we are in our calm, ordered Solar System, everything’s business
as usual. But if you look around, you realize it’s pretty amazing that
our planet is even here. Poor sideways Uranus is a testament to our good
luck.
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