Jump gates are one of many technological wonders left behind by the Coalite. They are made of an unknown substance at their core with various common metals in the surrounding structure. Using the gravity from a jump gate, a ship could pick up speed and "slingshot" itself into the cosmos. However, gravity is the only thing in the known universe that can stop an object travelling at speeds anywhere near lightspeed. Another jump gate ( or other object with significant mass ) would be required to slow the object to a "normal" speed. Not much else is known about the jump gates as the gravity is so great, nothing can escape it within a certain distance. Anything that travels close enough to a jump gate would be crushed beyond recognition and ultimately the compacted material would be infused into the core of the gate.