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Hank fields one of the most commonly asked questions about our solar system: Why does Saturn have rings? Part of the answer has to do with the fact that it's not the only planet that has them. Watch to learn more!

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The universe is chock-full of unanswered questions, as you know, but a lot of them have to do with our very own stellar neighborhood. For example: why does Saturn have rings?   It's one of the most common questions asked about our solar system, and while there is no single agreed-upon answer, understanding Saturn's rings might begin with the fact that it's not the only planet around here that has them. Jupiter has three very faint rings, Neptune has five, and Uranus has thirteen. So a better question might be: why do all of our gas giants have rings?   To answer that, let's start with an interesting little rule that celestial bodies tend to abide by, know as the 'Roche limit'. First identified by French astronomer Édouard Roche in the 1840s, this limit is the distance at which objects in orbit around a planet tend to be torn apart by the planet's gravitation. A planet pulls harder on the side of a satellite that's facing it, so if a satellite gets too close the unevenness of that attraction will likely cause it to break up. And that is apparently what happened to most of our gas giants, because with a few exceptions their rings are almost always inside their Roche limits, while the moons are outside.   So in the case of Saturn's rings, one prevailing theory is that billions of years ago some rogue wanderer, like a comet, got swept into orbit within Saturn's Roche limit and broke apart. Another model suggests that a moon that once orbited Saturn at a safe distance got smacked by a celestial object into the danger zone, where it disintegrated. By this logic, then, part of the reason why gas giants have rings might have to do with their size: they're just so big that they're more likely to draw in passing objects.   But their distance from the sun is important too. While the rings of Jupiter and Neptune are basically faint halos of dust, those around Saturn and Uranus are bigger and made up of almost entirely water ice, along with the volatile organic compounds that evaporate easily. So in addition to forming around large planets with big Roche limits, rings might also form more readily around planets where it's cold enough for the icy fragments of those crack-ups to survive. So you could say that Saturn's rings are just beautiful remnants of bad break-ups.   Thanks for asking, and thanks to all our Subbable subscribers who make this and everything you see here on SciShow possible. How'd you like an official SciShow chocolate bar, or one of our patented pocket protectors? To find out how you can score these and other perks, go to, and if you have a quick question you'd like us to answer you can find us on Facebook and Twitter, and, as always, in the comments below, and don't forget to go to and subscribe.