[Dragaera] Dragaera and Moons **Minor Vallista Spoiler, nothing plot related**

[Jon]

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So, in a Flashback in Chapter 6 of /Vallista/ we learn that Dragaera has 
(or at least at one point had) two moons. Bigmoon and Littlemoon.

This is noteworthy since other than the inferred existence of such a 
body based on the presence of tides, this is the first direct evidence 
of the number and characteristics of Dragaeran moons in any of the stories.

Based on what we see in the story, Bigmoon seems to be much like the one 
we are used to here on Earth.

Littlemoon, however, has the characteristic of not rising and falling 
every day--indeed, we are told it will be at least nine days before it 
will rise again.

A basic understanding of orbital mechanics reveals a few interesting 
things about this circumstance. Firstly, this means that the orbital 
period of this moon above the planet must be in fairly close proximity 
to the rotational period of the planet itself. Effectively, it means 
this moon must orbit at a point close to (but not exactly at) the 
natural altitude for a fully geosynchronous orbit. It cannot diverge 
from this orbital period by more than about 2 hours per day (given 
Dragaera's 30-hour day), however, or else it would always take fewer 
than nine days to appear again in the sky at any particular point on the 
surface of the planet.

Assuming that Dragaera is roughly the same mass as Earth, where the 
altitude for such an orbit is just a bit less than 36,000 miles, this 
must also mean that Littlemoon is a much smaller size (like a 
medium-sized asteroid) than our moon; it's small apparent size isn't 
just a matter of it being farther away from the planet than Bigmoon is.

Majikjon