Vectors Humans place too much importance in what they call velocity vectors, which are only a mathematical representation. The motion of asteroids or comets or planets is there for a reason. It is not, as humans frequently assume, because the motion was set in place for some reason long ago and things just follow. The motion is a result, not a primary force.
Humans treat motion as though it stood alone, outside of all other factors.
All motion is a result, from the acorn dropping from a tree, or the wind swaying branches as air masses move to equalize, to the motion of the planets in their orbits. The breeze that bows a young sapling over a bit will not keep that sapling bent when the breeze stops blowing. Just so, an object may even be stopped in its course, but only for a moment. An object will be motionless in space for one of two reasons. An object in the absence of gravity from outside influences has no reason to move at all, and is still only because there is no call to do otherwise.