Dirk Morgna is the real name of Sun Boy. The son of a brilliant scientist, Dirk and his friend Zarl interrupted Zaxton Regulus, a scientist at the facility in which is father worked, during an unauthorized experiment. The equipment Regulus was using exploded and killed Zarl. Dirk's father fired Regulus, who vowed revenge on Dirk. Attacking Dirk and knocking him unconcious, Regulus left him by a reactor to die, but the reactor instead gave Dirk the ability to project light and heat, like the sun.

Initially, Dirk applied to the Legion of Super-Heroes, but only showed his ability to project light. He was passed over for admittance, but later returned at the next opportunity and showed that he could also project heat. He was then given membership in the Legion.

Dirk serves as a pilot for the Legion Cruisers.