Starman

Jack Knight uses his cosmic rod and cosmic energy gun to fight crime as the superhero Starman.

Earth-One
Starman first appeared as a partner of the alien Martian Manhunter. The two operated in Gotham City for a bit before setting up a base on the Moon. While on the Moon they ran into trouble with three alien beings claiming to serve Eclipso. After seeing the belligerent nature of the three minions of Eclipso and hearing of Eclipso's evil intentions, Starman and the Martian tried to prevent them from digging up the black diamond they were looking for that contained their master. They did manage to find the diamond, and during the fight Starman was cut by it, allowing Eclipso to possess him.

Eclipso, using Starman's body, went down to Earth and tried to head over to Egypt to resurrect the Golden Pharaoh; however, Captain Marvel and Superman were able to stop him in a fight in the Sahara Desert thanks to the Shazam! lightning bolt of Captain Marvel.

Starman and the Martian Manhunter were later invited onto the Justice League. Starman remained an active member up until the events leading up to the resurrection of the Golden Pharaoh. Eclipso once again took control of Starman (still dwelling within his body the entire time) and went to Egypt and resurrected the Golden Pharaoh. The Justice League and several other heroes arrived and a large fight ensued. Superman was able to trap Eclipso in an ancient cavern underneath tons of ancient debris and rubble, where he (along with Starman) presumably died.

Earth-Two
Starman later appeared on the parallel world of Earth-Two working with the terrorist organization of Kobra because he was being mind controlled. Lord Naga had taken his body and bathed him in a Lazarus Pit back in Earth-One, and then brought him to Earth-Two with his interdimensional traveling technology. Green Lantern was able to use his magic ring to nullify the mind control effects, and Starman then became an ally of the Earth-Two heroes.

Starman has appeared several times as an ally of the trio of Green Lantern, Hourman, and the Atom, such as in their fight against OMAC, the hunt for Batman, and in the group's second fight with Superman.

Personality
Starman is one of the most brilliant scientists in the field of astronomy. The fact that he currently resides in a less technologically advanced era makes him stand out even more prominently.