Comet

Comets are icy asteroid-like bodies that orbit stars in large and long long orbits. In the game, they go straight to stars and then turn back a complete 180 degrees, until they reach aphelion, then turn around 180 degrees again. Comets are a great source of material if you can harvest them. A few things to note:

1. Comets, like asteroids, have too little gravity for infrastructure based colonies.
2. Comets move slowly, but surely, on very large, irregular orbits.
3. Comets do not leave their system, but they will go billions of kilometers away from their center of orbit before returning.
4. Comets can be mined with both Asteroid Mining Modules and Automated Mines.

Obviously they provide a unique challenge, but can be quite valuable. Comets often have as much material as a small mineral rich planet, with the accessibility of an asteroid. A good way to tap them is to drop as many automated mines as you can and a mass driver on them while they're close, then use the mass driver to deliver the minerals to the most convenient stable solar body, be it a permanent colony or a way-asteroid to be freighted through a jump point. Since the packets neither slow down nor collide, even if the comet moves to the other side of the system the minerals will still reach your colonies eventually.