We often read about the speed of light, various individual particles, etc.<br /><br />What, however, is the fastest that an object of 'concrete size' is currently moving through space. <br /><br />What is the fastest speed we can speculate a solid object is moving? Is it an isolated pebble-sized rock? A planet? a star? A galaxy? Is it ejecta from a supernova explosion or does that not send out material other than particles?