I found this story in an old copy of a Superman's Pal Jimmy Olsen from the 60s (actually it is a reprint from a copy of 80-Page Special from '64 so I don't know how old the real story is).
Boy, they sure made Superman too powerful sometimes. It was like they didn't understand just how powerful they were making him. Here we see that Superman created a solar system.
Some star burned out, far from Earth, and caused the beings that lived on the planets that revolved around it to evacuate. Superman goes to help. "Speeding there, I gathered millions of meteors and fused them together, constructing artificial planets for these homeless people. Finally, finding a burned-out star, I rekindled it into a blazing new sun with an atomic match."
Later on in the comic, featuring Jimmy Olsen becoming the adopted son of Superman, we actually see Superman PUSHING another sun into the place of the one he created, which had gone dead.
He is pushing a sun. He is pushing a sun from someplace to someplace else for this solar system. He is creating a new solar system, not from scratch, but he is still making a new solar system.
Didn't the writers and editors see this as a problem? How do any villains, super-villain or otherwise, ever pose a threat to Superman anymore after an episode like this? Even cataclysms don't seem scary if we see him pushing celestial bodies around. This is why some people have always liked Batman better for being a real human. Superman at times has been just way too powerful.
Also, this brings up a new point with the movie Superman Returns. At the end, when Superman lifts up the new island, even if most of it is Kryptonite, depending on your knowledge of what Superman has accomplished before, lifting this island doesn't seem that drastic.