• Question: Why do some planets have rings around them?

    Asked by Pheebs to Scott, Ry, Maggie, Daniel on 15 Nov 2017.
    • Photo: Ry Cutter

      Ry Cutter answered on 15 Nov 2017:

      Saturn has a pretty big gravitational field (for a planet). We think that one of Saturn’s moons got too close and was torn apart by Saturn’s gravity. This is really useful though because it means we can see what the composition of the moon was like. It also looks really cool 😀
      Other planets get their rings through similar processes. Comets and asteroids get too close and a ripped up. The debris then orbits the planet.
      Saturn’s rings are some of the first ‘disc-like’ structures we’ve seen in the universe. Which are important for gravity theories and theories for planet formation!
      Fantastic Question,
      Ryan

    • Photo: Scott Melville

      Scott Melville answered on 15 Nov 2017:

      Ryan has it covered – but I want to share some cool pictures. This is actually something called the ‘Roche limit’,
      https://en.wikipedia.org/wiki/Roche_limit
      i.e. if you get too close to a planet, then the gravity is enough to tear big things apart into neat discs.
      The picture on Wikipedia is good – but this picture is also pretty helpful:
      http://abyss.uoregon.edu/~js/glossary/roche_limit.html
      basically because different sides of a moon would feel different forces, the two sides get slowly torn apart 🙂 Super pretty though!

    • Photo: Maggie Lieu

      Maggie Lieu answered on 15 Nov 2017:

      In our solar system only the giant gas planets Uranus, Neptune, Saturn and Jupiter have rings. The smaller planets don’t. This is because the rings are formed from asteroids, comets and other debris that get caught in the gravity of these massive planets.

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