How to create an annual celestial event for a world
Yesterday while Green, Andy and I were recording new episodes for the podcast we stumbled upon a bit of a problem that we need someone with physics/astronomy knowledge to help out with.
We want to create an annual astronomical event for the sake of one of our species hosting a once per year festival/gathering.
The world:
- Earth-like
- Axial tilt is slightly more pronounced at 27%
- The planet has two moons, their size and distance from the planet are undecided and may be tailored to fit this scenario.
- A 12 constellation Zodiac similar to Earth
One of the constellations in the Zodiac is a cat and each year we would like some astronomical event related to the constellation to happen.
The event:
- Must be tied to the cat constellation
- Should take place in the fall
- Will ideally include one or both moons
- Can only happen once per year
- Needs to be visible from anywhere within 20 degrees latitude of the equator
This post was sourced from https://worldbuilding.stackexchange.com/q/105501. It is licensed under CC BY-SA 3.0.
1 answer
One of the moons is the size of Earth's moon, and has a semi-major axis of around 413,277 km. This gives it 12 orbits a year.
The moons orbit is such that it is full while it is in the constellation of the Lynx.
This moon is young in cosmic terms, and so isn't tidally locked. It has a feature where a combination of craters and exposed olivine rich rock on the surface closely resembles a cat eye.
The rotational period is slow, so that with every orbit 1/12th of a day passes, and is synced so that the cats eye face is visible during the full moon while it is in line with the constellation of the Lynx.
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