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script-a-world · 6 years ago

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Can you tell me about creating my planet for someone who is dumb as a doornail with astronomy and my research keeps giving me information I do not understand. My planet has an oval orbit like Sedna and twice the size of earth and has 3 moons, sizes like Mars, Triton, and Pluto, the last one with a weird orbit like Hyperion. What do I do with the weather on different parts of the planet, the tides, and how is the moons' and sun's path seen from the planet?

Tex: The amount of detail you've given us indicates to me that you already have a good chunk of the foundational knowledge that you need to orient yourself on the topic - please don't stress about what you don't know! You don't need to be an expert on the topic, and there's a lot of wisdom in asking for help.

Orbits are tricky things, and the oval ones you're mentioning are called elliptic orbits. Juggling these many celestial bodies at once would mean being familiar with the concept of barycenters, since you're going to need two fixation points - the planet all these moons are orbiting, and the sun that the planet is orbiting. That quickly gets into a lot of math, but for now you just need to set up your reference points to better visualize things.

I can see right away that the relative sizes of your celestial bodies means that either your planet is further away from its sun than our Earth is, or your sun is proportionally larger than Earth's in order to compensate for the gravitational effect your planet has on its satellites. Jupiter is a good example of why these parameters need to be set up, in order to determine the relative size and distance of your planet's sun.

I'm going to eyeball your set-up and guess that with a planet double the size of Earth, it's possible to be either twice as far from its sun, or the sun is twice the size of ours, or the sun is half its size (which would be... interesting to see). There are, of course, exceptions when it comes to the relative sizes of planets and their satellites, of which Pluto and Charon are a notable case (Strobel’s Astronomy Notes).

Hyperion is a funny oddball. It straddles the lines of technicality between natural satellite and asteroid that's caught in someone's backyard, and I would hazard a guess that its orbit is partially caused by its porous, aggregate form. Personally I wouldn't count it as a moon, though it could be considered a proto-moon that hasn't been in your planet's orbit long enough for its gravity to shape it into a proper sphere. I don't know more details about this configuration, so it's possible that it could go crashing into one of the moons soon, if it doesn't fling itself out of orbit at the slightest provocation.

Most moons, but not all, are tidally locked with their planets, which is the phenomenon that would create an effect on ocean tides. There's not much I can say on that which isn't already covered by the link, so you'd have to come back with more specific questions on that one.

As for the weather - this isn't dependent upon satellites, but rather the rotational speed (AKA Coriolis Effect; SciJinks, Polar Satellite Meteorology and Climatology at CIMMS) and axial tilt (National Weather Service) of the planet (to a lesser degree, also solar radiation, but currently that's a more progressed topic). Wind is the driving force behind most meteorological phenomena, and acts independently of satellites like moons - however, the amount of layers in the sky also dictate what types and patterns of weather are available to your planet.

I think that wind isn’t majorly dependent upon how active the core is, despite a planet’s overall and core sizes being related to each other (PDF page 5, PDF pg 12), so the relationships between astrogeology and weather are weak at best.

If you're technologically-inclined, you could create an orrery with this GitHub code (from this previous question), which would help you visualize your moons and sun from your planet's perspective. If not, there's certainly plenty of ways to make a physical orrery, or else a solar system mobile.