When Al fought a reluctant supervillain named Cyclotron he was exposed to "thorium radiation" and, as a latent effect of that battle, he gained super strength in 1948. He also gained powers from an incident at the Manhattan Project where Al ran carelessly into an area full of extremely high levels of radiation to save his friend Ted Knight, the original Starman. Then he decided to update his costume to the one seen here!

Head: fodder
Body: DCUC JSA Atom