Planetary Profile: Jumbo Jupiter

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It’s been a hot minute since I added an entry to my weird solar system blog series (here’s Mercury, Venus, Earth, Mars, and the asteroid belt), which means it must be time to move on to the Big Guy: Jupiter!

Y’all, this planet is so darned bizarre in so many ways, that there’s really too much for me to include everything in a single post, so I won’t bother. In fact, some of the weirdest things about Jupiter are things I’ve already mentioned in other blog posts, so if you want to hear about Jupiter’s tendency to collect asteroids, the uniquely harmonic nature of its big moons, or that time it almost went homicidal on the entire inner solar system, please feel free to read those previous posts. But don’t worry, that will leave plenty left over for this post to dive into.

So let’s get to know our solar system’s chonkiest planet, the mighty Jupiter!

Going to Extremes

When I say Jupiter is chonky, I mean you could fit all of the other planets inside of it and you would still have room to spare. That’s how freakin’ large this planet it. If you wanted to fill it up with only Earths, you’d need over 1,300 of them. Jupiter is truly, epically, ridiculously ginormous.

Okay, now that we’ve gotten that out of the way, I should probably point out that while Jupiter’s size is probably its most well-known extreme, it’s certainly not the only one. For instance, Jupiter also spins faster than any other planet in the solar system. It whips its massive bulk around once every ten hours or so (in 9.9 hours, specifically).

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This rapid spinning and its gaseous makeup means Jupiter is notably non-spherical. The planet is thick around the middle. In fact it was only last week that we were able to use data from the Juno mission to refine our measurements of Jupiter’s size, with new measurements putting it at about 88,841 miles (142,976 km) across at the equator and about 83,067 miles (133,683 km) across at the poles. Yes, it’s over 5,000 miles (8,000 km) thicker across the middle than pole to pole. I told you it was thick in the middle.

This rapid rotation also plays a big role in forming Jupiter’s distinctive atmospheric bands, those boldly colored stripes that make up its outer atmosphere. The planet’s rotational speed is creating strong jet streams that separate its clouds into those bands—a pattern not seen so distinctly on any other planet. Jupiter is definitely stylishly dressed.

And, of course, strong jet streams are good for making storms.

Seeing Red

If there’s one thing people know about Jupiter when they come into the Planetarium, other than that it’s rather sizeable, it’s that the planet has a famous storm, the accurately but not creatively named Great Red Spot.

It’s only one of a large number of cyclonic storms dotting Jupiter’s surface, but it’s definitely the biggest and most notorious. When Galileo first stuck his eye to a telescope and observed Jupiter in the 1610s, he saw the Great Red Spot. Or, well, he saw a Great Red Spot.

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We used to assume that the storm we see on Jupiter today is the same one Galileo saw, but new evidence disputes that. For one thing, today’s Spot is shrinking. We’ve seen it be over three Earth’s wide, and now it’s less than one Earth across, and is losing nearly 600 miles (966 km) from its radius each year. It may soon vanish, which would be weird if this was a storm that had been stable for centuries.

But there’s also the fact that nobody observed the Spot on Jupiter from 1713 to 1831. That’s a weirdly long time for literally every astronomer on Earth to lose track of a super storm. The thinking is that Galileo’s Spot vanished sometime in the 1700s and a new one formed sometime before 1831. That the storm we’re seeing right now isn’t centuries old, but only around 190 years (of course, that’s still rather ridiculously old for a storm).

It may be that this storm system is something that cycles, and we’re at the point in the cycle where it’s preparing to vanish. Maybe it will come back in a century or so, maybe it won’t. In any case, it’s definitely bizarre.

It’s What’s Inside That Counts

Thus far I’ve really focused on Jupiter’s outermost features, but its insides are…well there really isn’t any other way to put it, they’re weird, in many ways and in many layers. Let’s start by going all the way down deep to the core.

For a long time we had two major theories for Jupiter’s formation. One is that the whole thing just sort of condensed out of the protoplanetary disk surrounding the baby Sun in the solar system’s formative years. Another is that the planet’s ridiculously thick gas layers originally built up around a solid rocky or metallic core. In the first version Jupiter wouldn’t have a distinctive core region. In the second, it absolutely would. 

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Of course adhering to one or the other of these would lessen Jupiter’s overall weirdness, so naturally neither of these seem to be fully correct. Data from the Juno mission suggests that Jupiter does have a core region, and in fact a larger one than we used to think. Only calling it a distinctive core isn’t quite accurate. It’s more…fuzzy. There doesn’t seem to be a clear point of separation where the core ends and the gas layers begin, because that would be too simple.

It’s possible this fuzzy core is a result of a massive impact in Jupiter’s past. Or, you know, it’s possible this planet is just weird. At this point I wouldn’t want to bet against that second option.

Moving on from the core, Jupiter’s makeup is largely of hydrogen (about 76%, with most of the remainder being helium). But the deeper you go into the atmosphere of a gas giant, the higher the pressures get, and Jupiter has a lot of depths to reach. Deep enough and hydrogen, so happy to remain gaseous under most circumstances, gets compressed enough to become a liquid. This means the largest ocean in the entire solar system can actually be found deep within Jupiter’s layers, a thick, dense ocean of liquid hydrogen, and don’t tell me that’s not weird.

But just to make it even odder, when you go down even farther the pressure is so high that the electrons get squeezed off of the hydrogen atoms, which makes this ocean as electrically conductive as metal—liquid metallic hydrogen. The planet’s rapid rotation generates electrical currents in this region, helping to drive the formation of another specialty of Jupiter’s extremity: its off-the-charts magnetosphere.

Sheer Magnetism

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When I say that Jupiter’s magnetic field is ridiculous, it’s really hard for me to find a way to put it into perspective. Our puny human brains have a hard time comprehending these sorts of extremes, but suffice to say the magnetic field is so powerful that it has sucked up enough charged particles (from the Sun and from Io’s volcanoes) to turn the region immediately around Jupiter into a Total Radiation Death Zone. Hanging out in this region would instantly expose you to well over 1,000 times what would be considered a lethal radiation dose. Your organs would be toast.

And even spacecraft with shielded electronics can’t survive there. Anything we put into orbit around Jupiter (okay fine, thus far that’s only Juno and Galileo, but Europa Clipper and JUICE are currently on their way) gets a highly elliptical orbit allowing the spacecraft to occasionally do a rapid dive bomb into the Death Zone and get close-up observations of Jupiter and its moons while spending most of its time well away from the radiation belts.

We have to do it that way, otherwise our spacecraft would rapidly get destroyed. In fact, Galileo almost was during its first close flyby because it turned out we had underestimated just how radioactive the belts were. Whoops. And, although Juno has been serving faithfully since it entered Jupiter orbit in 2016, there are signs that the repeated radiation exposure is getting to it. In the end, the radiation will probably be what finally ends that mission.

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Okay, so maybe that helps you get an idea of how strong Jupiter’s magnetic field is. Maybe. But what about appreciating its size? Nothing with Jupiter comes small (except its ring, somehow the biggest planet has the dinkiest, saddest ring system), and the planet’s magnetosphere is, appropriately, stupid big.

Like Earth’s it has a shorter blunt front end facing the Sun (the magnetopause) and a long, trailing tail behind it (the magnetotail). Jupiter’s magnetopause can stretch as far as 50 Jupiters in front of the planet (that’s over 4.4 million miles or 7.1 million km, but how often do you get to measure things in Jupiters?). Which is far, but nothing compared to the long magnetotail, which has been known to extend well past Saturn’s orbit about 500 million miles (800 million km) away.

The only larger single structure in the solar system is the Sun’s heliosphere. Jupiter’s magnetosphere is seriously ridiculous y’all, and no other planet comes close.

Weird Giant

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That, naturally, doesn’t mark the end of Jupiter’s oddities, just the amount I can fit in the number of words I allotted myself for telling this story. And of course, I didn’t even touch on any of Jupiter’s moons, several of which are extremely bizarre worlds in their own rights (actually…do I want to do an entry in this series about some of weird moons? Hmmm…). 

And on top of all that we have two spacecraft on their way to the Jupiter system right now. Europa Clipper and JUICE (the JUpiter ICy moons Explorer—yeah, I know, not how acronyms work). While their ostensible mission is focused on the moons, they’re not going to ignore the humongous gas giant in their midst! When these spacecraft arrive in system in 2030 and 2031 our knowledge of Jupiter and its moons is gonna take a giant leap. I am, shall we say, abso-freaking-lutely thrilled!