We have no idea how much mass that ship has, or if it has contragravetic measures like a lot of ships in Bungie games have.
So the answer is "maybe."
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I didn't say anything about a moon, but until we know what it's made of, apparent size is not directly proportional to mass. That said, the average diameter of Deimos (one of Mars' moons) is 12.4 km, which (approximated as a sphere) gives us a surface area of 483 km^2. There are 198 cities in the world with more surface area than that, so yes, it could be called a moon.