Actually there is no such thing as a stable orbit in Eindsteinian mechanics (except for 2 point masses orbiting eachother. There is no such thing as a point mas

Actually there is no such thing as a stable orbit in Eindsteinian mechanics (except for 2 point masses orbiting eachother. There is no such thing as a point mass in reality). So the energy conversion from speed to distance and back is not 100% efficient and an asteroid (or the Earth, for that matter) is doomed to eventually fall into the sun or fly away from it forever. It cannot keep circling forever, even in a theoretically perfect situation. In addition to that, the tidal forces will compress and decompress the mass of both objects, which effectively converts potential energy (the distance between the two objectds) into heat. Even though the moon is on a trajectory to eventually leave earth orbit, every tide that comes in and leaves lowers the rotation speed of the moon. While the moon has no liquids on it's surface, which makes the effect nearly invisible, it does have tides (slight variations in the angle and magnitude of gravity at it's surface) which move objects around and the energy for that does indeed come from orbital decay. Similarly, the earth loses orbital energy to the sun.