To accurately represent the asteroid moving through an emptier part of space where it is farther from the gravitational pull of other objects, the student should adjust the model to reflect less gravitational influence. The most appropriate change from the options provided would be:
1. Straighten the rope.
Straightening the rope would signify that the gravitational forces are weaker and that the asteroid is moving in a more direct path through space, rather than being influenced by the pull of other objects.