Can you help me write this Science Fiction book about the cigar-shaped planet?
Haumea is a real (not fictional) dwarf planet from our solar system with a shape similar to the shape of a rugby football.
I want to make a science fiction book with an alien civilization living on a planet with this shape.
Please help me to understand better the laws of physics and astronomy applied with this dwarf planet Haumea. What conditions would be on such planet? Lower gravity at the poles? Would a normal planet like Earth have this shape or it would have to be smaller in to have this shape?
The shape of the rugby football is given by the rapid spinning around its axis. How much can a rapidly spinning planet around its axis support life
I am asking only people who know astronomy this question. And those who have read SF books.
My fictional planet would not be very far from the Sun as Haumea is. My planet would be where Earth is, in the habitable zone
Alright… let’s think. Firstly, I get the idea that it would mostly be smaller planets that would have this shape, but I don’t know if something with the mass of Earth would be too large. Far as I can think, it would need to be small to overcome gravitation enough to get into that shape. Technically, the Earth isn’t a perfect sphere either; it’s an oblate spheroid. The diameter from North Pole to South Pole is different from diameter between opposing points on the equator, but the difference is less than 1%. This is due to the Earth’s spin. So… I suppose you’d need to have a smaller planet and/or much faster spin to get that shape; if you make it small AND fast, then it would be better than having it Earth-size and ridiculously fast, or Earth-speed and ridiculously small, if that makes sense.
I assume there would indeed be lower gravity at the poles than at the equator, since the poles are further from the centre of gravity. As to how much, I can’t say exactly, but the square-cube law should give you an approximation that’s good enough for believable fiction. That is, say the gravity at the equator is 1G, and the diameter at equator is half the diameter at the poles. That would make the gravity at the poles 0.25G. I think that sounds about right anyway, although you might wanna check in the Physics section for this. And, to be honest, all the more technical questions.
As for life and civilisation, remember that if the spin is a lot more rapid than Earth, you’re going to have much shorter days and nights. You’ll need to take that into account when you’re thinking about animal life and it’s sleep cycles, or whether species will actually follow that day/night cycle and only be awake for short periods followed by short periods of sleep. (If your creatures even sleep at all of course, since we’re talking aliens here.
) That’ll also affect climate and weather, especially in desert regions where temperature changes are more drastic between day and night.
I’m not sure if the rapid spin of the planet would cause any centrifugal/centripetal effects that would impact on biology. Or, to be more precise, I think there would be effects there that you’d need to take into consideration, but I really don’t know what would happen. So overall I’d advise asking again in the Physics and Biology sections.
Well the most important thing is that it has a mass of .07% of the Earth. Near as I can tell, the forces that formed it into this shape wouldn’t have worked on a larger planet, closer to the sun.
I admit to not being an astrophysicist, but I would read such a story. It reminds me of a lot of the old golden age stories. I’d recommend getting as many scholarly articles as possible as to likely environments.
Good luck, i’ll be looking for this story.
Current thinking is that Haumea is the shape it is because of a collision with another object. When planets and moons form, those above a certain mass tend to settle into a spherical shape under their own gravity. If they don’t, it may be because they cooled too rapidly. I think they would have to be far from the sun for this to happen, and/or be made of something that doesn’t retain heat very well. So a planet like Haumea is probably going to be colder than Earth.
Gravity would be lower at the pointy end – use Newton’s law of gravitation to work out how much lower. A planet that spins rapidly bulges at its equator. If the pointy ends are at the poles, rapid spin would tend to squash the planet back towards a more spherical shape. If the pointy ends are on the equator, rapid spin would tend to spread them out, so that the planet assumes more of a discus shape. I don’t think rotation alone could give the planet the shape of a rugby ball. It would have to be a collision or (if your aliens are very advanced) deliberate engineering.
Winds and tides (if the planet has an atmosphere and/or oceans) would be quite complicated – even more so than on Earth.
If the planet is in an orbit like Haumea, it’s going to be very cold and dark. Haumea’s average surface temperature is -220 C. The Sun is just a brighter-than-average star. The natives might live underground, or in the oceans, where conditions would be a bit more stable than on the surface. Unless they have access to the surface, they’ll probably be blind, and will have other senses for finding their way around.
EDIT: If this planet is in the habitable zone, then it might stay warm enough that it stays sufficiently plastic to form itself into a spheroid. Any sufficiently large object will do that, given enough time – it’s a consequence of the law of gravity.
If it’s small enough to stay cigar-shaped, it’s going to have trouble holding onto an atmosphere, unless it also has a strong magnetic field to deflect the solar wind. (Current theories are that this is partly why Mars’ atmosphere is so thin.) But a small planet might not retain enough internal heat to keep its core liquid, or might not have enough magnetic material in the core to generate a strong enough field.
You might get around these problems by having the planet in transition – big enough to become spherical, so it has an appreciable atmosphere and a magnetic field, but it hasn’t become spherical yet. In this case, the planet would be excessively prone to earthquakes and volcanism.