Suppose that a rogue planetoid were to enter our solar system from parts unknown and barrel towards us. To make this specific, let us suppose this object is about the size of Ceres, the largest object in the asteroid, so it’s about 470 kilometres in diameter. We’ll call it Achilles because I can’t think of any celestial object called that and it’s mythological. The Moon is about 3500 km in diameter, so while our new friend is way large enough to be spherical, it is quite a lot smaller than the Moon.
If it HITS the Earth we’re all dead meat. But suppose it does not, it just gets close. Is there some way Earth could pick this thing up as a second moon without it smashing into us and blowing us all to smithereens? Is a contactless capture possible?
Would it be possible for such an object to assume a stable orbit inside the Moon’s orbit?