Worldbuilding & Astonomy: What’s the second biggest thing in the solar system? And you think you’re going to mine a gas giant?

So, yar, here’s a question for you:

What is the second largest physical object in the solar system?  (No, not made up stuff like “The orbit of that planet that lost its charter!” – the orbit isn’t a physical object, it’s what we use to describe a particular path, but I’m talkin’ something that exists all at once largest.)


Ah, yes, I see your hand up there, Mr. The Science Geek.  And I’d let you answer, but I gotta finish this blog post and I can’t quote you if I don’t actually have a quote. But it’s what you’d answer if you were here. Which you’re not. You’re in Great Britain, or technically, England, which brings me to all that third grade stuff of subsets, sets, and so on.  England is a subset of Great Britain. But everyone uses ’em interchangeably anyway.


The answer is the magnetosphere of Jupiter.

BOOM! Maybe you were thinking the answer was “The Sun!” And that’s not correct either. Technically, the largest object is the Heliosphere, which is the region of space dominated by the sun, or its particles. That extends beyond the imaginary orbit of pluto you were trying to stick in up there.  I saw you guys.  Just admit it.

The magnetosphere is this amazing HUGE HUGE HUGE “cavity created in the solar wind by the planet’s magnetic field,” says the anonymous people at wikipedia, who never lie or twist things to their own happy little wikirelativistic viewpoints. Anyway, here’s the conclusion of that fine article:

In 2003, NASA conducted a conceptual study called “Human Outer Planets Exploration” (HOPE) regarding the future human exploration of the outer solar system. The possibility was mooted of building a surface base on Callisto, because of the low radiation levels at the moon’s distance from Jupiter and its geological stability. Callisto is the only one of Jupiter’s Galilean satellites for which human exploration is feasible. The levels of ionizing radiation on Io, Europa and Ganymede are inimical to human life, and adequate protective measures have yet to be devised.

What a nice way of saying YOU WOULD BE RADIATED TO DEATH IN A FEW MINUTES WITHOUT A COUPLE TONS OF LEAD TO PROTECT YOU.  Really. Pleasant. “Inimical to human life.” Written by a scientist. Where’s the passion? Where’s the love? Say, “you’ll be KILLED IF YOU LAND HERE!”  See how much better that pops?

Ah, so you’re writing a book, like you do.  Lots of those being written around here. And lo and behold, you decide “I’ll just have everyone refuel at the magic HE3 depository in the local gas giant. Cause, well, cloud scoops are easy. Go cloud-scoops!”

See, there’s a little tiny problem with that. Unless they’re robotic cloud scoops, the chances of you getting close to a gas giant are pretty minuscule. (Yes, I spelled it right. No little “i” for that word.) BUT WAIT! Just because Jupiter has this huge nasty solar plasma die-all-life thing going on doesn’t mean all gas giants do. Bad ol’ Jupiter is different. It’s got its own issues. What about that nice boy living next door, Saturn?

I’m glad you asked. Saturn has the same durned problem.  Big ol’ magnetosphere, which must be an interesting interaction when Jupiter’s Magnetosphere interacts with Saturn’s Magnetosphere.  “You got your chocolate in my peanut butter,” they might say, if planets talked and stuff. Which they don’t, mostly, unless you’re writing moonbeam sci-fi and you’re a big proponent of medicinal marijuana, for your hypochondriaca melencholia.  Jupiter’s magnetosphere extends into the orbit of poor ol’ Saturn.  I haven’t seen any writing on the subject of that interaction, though it might be because the two planets line up every 20.47 years or so.

[Quick! Algebra problem. Planet J orbits the sun every 12 years. Planet S orbits the sun every 30 years. How often will the planets line up? Show your work. I think it’s… well, 12/30 = .4, so Saturn travels 40% of its complete orbit in the time it takes Jupiter to go once around. So Jupiter has to catch up, and that means it has to travel an additional 40% of its orbit, which is 12*.4 = 4.8. It would take Jupiter 16.8 years to catch up with Saturn each time.  But… Saturn is still moving, so it’s actually higher. Math is not Mongo’s strong suite, yanno? I found this equation. Mongo fail. The answer is 20.47 years. I blame Kepler for this misunderstanding.]

Magnetosphere of Jupiter was discovered in 1973. So they had, at the most, two opportunities to study this complex interaction, and considering that the measurements of these two things come from spacecraft flying by, it’s impossible for anyone to know this.

We have two gas giants, both of which exhibit the same sort of affect on the sun’s plasma streaming by. Perhaps your gas giant is different, and managed to escape all those pesky magnetic fields generated by the the enormous amount of metallic hydrogen in the center.

Or maybe, in your universe, someone solves the blamed problem by inventing a miracle armor.  I wouldn’t put it past y’all to do that.

Go ahead, comment. It won’t kill you.  And, um, it’s not because I’m desperate. Because I’m not. I’m NOT! Just comment. If you comment, I’ll be your best friend!  C’mon. I’ll give you a cookie! Yeah, I love the “Don’t Let the Pigeon Drive the Bus” books, too.


2 thoughts on “Worldbuilding & Astonomy: What’s the second biggest thing in the solar system? And you think you’re going to mine a gas giant?

  1. In general, space is a pretty dangerous place. It’s pretty much the magnetosphere, and some atmospheric effects, that protect us from most harmful radiation from the sun. I suspect, though I’m no physicist, that if you had a strong enough magnetic ‘bubble’ around your ship you could probably reduce the effects of a lot of that radiation. That said, it would take a pretty powerful energy source to produce such a thing. Since you’re travelling around in space though, presumably at very high velocities, you’d almost certainly have a powerful energy source and so maybe this wouldn’t be quite as difficult to achieve as it sounds? Also, I like the don’t let the pigeon drive the bus as well. I had it memorized there for a while. For the cookies, if give a mouse a cookie is also an excellent children’s book, though I really prefer if you give a moose a muffin.


  2. Maybe they don’t talk about the magnetosphere because they’re showing, not telling and avoiding the infodump. Heh. See what I did there? I suppose talking about magnetosphere might just kill the mood in a story. But it still seems like a big omission of something that’s the 2nd largest object in any solar system.

    I wonder how it works with a binary and a gas giant? That’d be fascinating.


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