The Fast Protosun is a peculiar protosun of extragalactic origin made up of antimatter orbiting in the edges of Known Space outside of Human Space.[1]
The protosun was described as glowing with a dull red glow despite its mass being too spread out and thin to have started nuclear fusion. This was later thought to have been caused by interactions with normal matter heating its mass.[1]
The protosun was orbited by one lone planet known as Cannonball Express. There were no asteroids or other planets in orbit, probably having been eroded away by antimatter-matter collisions. The protosun's system was as well filled with radiation caused by these interactions with normal matter.[1]
The location of the protosun and its system was revealed by the Outsiders to Elephant and Beowulf Shaeffer in exchange of one million stars.[1]
The closest inhabited world to the system was Kzin.[1]