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Comment by elihu | Hacker News Reader

> In fact, the planet, known as WASP-39b, has three times as much water as Saturn does.

Is that a lot?

That's exactly what I was wondering! It's such an odd choice to compare it to as I'm having trouble finding an exact number. This article mentions that it's a small amount of ice but not exactly helpful for a scale: https://www.universetoday.com/15374/is-there-water-on-saturn...

So there's little water on Saturn! but wait, since Saturn is about 300 times the size of earth, and Earth's mass is just 1/4000th water, I'm still utterly confused as how much it is compared to us.

Odd choice, indeed.

Saturn is big! And it looks blue!

Must be a lot!

Saturn looks blue? https://www.jpl.nasa.gov/spaceimages/details.php?id=PIA00400

What blows my mind is that Saturn in that image looks almost exactly like it does in the intro to Star Trek The Next Generation, which I always chalked up as bad CGI.

Try seeing it through a powerful eyepiece telescope. It’s absolutely one of the most astonishing experiences I’ve ever had.

Consider this image is from Voyager. Cassini captured much higher resolution ones.

Higher res maybe, but it still looks amazingly fake:

https://saturn.jpl.nasa.gov/resources/7549/?category=amateur...

I guess what's messing with me is that it just looks so smooth, which life-long exposure to CGI has taught me to mean that it's fake.

This reminds me of what Elon Musk said about his Tesla in space: you can tell it's real because it looks so fake.

Oops, I was thinking of Uranus! What hope!

Maybe Neptune? Would make more sense.

Yes, that’s the one! I don’t know, Outer Planets all look the same to me.

Oh, c'mon, they are named after specific Gods after all.

Probably thinking Earth

Silly, but this always cracks me up.

Hard to say, without being converted into units of jumbo jets or football fields.

I think the relevant metric here is Olympic swimming pools.

But how big is it in terms of Belgium?

There are three regions in Saturn's troposphere and the lowest region, about 130 kilometers (80 miles) down, is largely clouds made of water and ice. https://www.esa.int/Our_Activities/Space_Science/Cassini-Huy...

It's hard to measure absolute water abundances (it requires a lot of assumptions and extrapolating). This is a relative comparison of atmospheric water. We don't have relative water abundances for a lot of planets, so it's on the higher end, but we don't really know (maybe some other planets' water are hidden behind clouds).

That makes me think it’s a pretty substantive amount of water. If we’re getting 3x the spike we see for a planet in our own solar system in a planet lys away then actual content should be much more (due to signal/noise? Just guessing though)

It's not the absolute value of the signal. What they're measuring the amount of water compared to hydrogen.

Hm, Saturn is a gas giant with average density less than water.

I distinctly remember learning that Saturn would float in a bathtub at gradeschool!

That sounds... less than accurate. Will a sponge float in water? It's less dense...

I'm trying to imagine how the result of a close encounter between Saturn and a Saturn-sized bathtub full of water could be anything other than a single merged sphere with a lot of water content.

A sponge is less dense because it’s full of air holes. But yes, any such encounter would likely tear both “masses” apart and form a new planet.

Right, and Saturn is less dense than water because it is mostly composed of air. It's like a sponge with the spongy lattice removed. It's not a solid. (At least, the vast majority of it by volume is not a solid.) That's why it's called a "gas giant".

I was going to say that it would be a star, but apparently (making an assumption about the mass of the saturn-sized bathtub full of water here) it would still be orders of magnitude from ignition.

An Olympic swimming pool scaled for a Saturn-sized swimmer on the other hand... Ignition!

You’d need on the order of hundred times the mass of Saturn to create a red dwarf, so the swimming pool might actually be enough to kick it into being a Sun-sized or even larger star.

Sounds like the kind of ridiculous lesson one files away when they realize their critical thinking skills have surpassed those of the teacher.

Well, it's a lot more than on Mercury.

It’s relative, a lot compare to earth but otherwise, it doesn’t mean much to ask that

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