Jo Nah is the real name of Ultra Boy, a member of the
Legion
of Super-Heroes.
While traveling in space, Jo Nah's ship was swallowed by an energy
beast. He was cut out by a Galactic Patrol Cruiser, but not before he
was suffused with radiation from the monster. Jo Nah found the radiation
allowed him to be super-strong, invulnerable, super-fast, or see through
anything, including lead. The only limitation was that Jo Nah could
only possess one of these abilities at a time. Calling himself
Ultra Boy, Jo Nah applied for and was accepted as a member
of the Legion of Super-Heroes.
Ultra Boy faked a criminal past to gain the trust of space
raiders at one point in his Legion career. He was expelled
during that time and only after being persued by his Legion teammates
and defeating the raiders, was he reinstated.
Ultra Boy is romantically involved with Phantom Girl.