why do comets take a sharp turn near the sun instead of continuing past it a longer distance that’s more equal to their voyage toward the sun?

Question

The orbits of comets seem a lot different than for moons which have an elliptical orbit that’s roughly equal on both ends as it falls toward its planet and perpetually ‘misses’ as the planet will have moved from its position by the time the moon would get there… and same for planets orbiting their stars.

So why do comets get so near to the sun? Shouldn’t they ‘miss’ the sun by a longer distance since they started out from so far away?

In: Physics

Answer 1

The main issue is how much angular momentum they have with respect to the sun (or other body being orbiter). Starting from a great distance away they have time to accelerate a lot toward the sun from its gravity, but they don’t have the momentum to the side to form a roughly circular orbit like the planets do.

As they get in close to the sun the angle of the sun’s gravity starts to change and the relatively greater force of gravity pulls their path around, pointing their momentum from falling toward the sun into pointing away from it. Then it coasts outward being slowed by gravity until it falls back in.