The amount of energy needed to be absorbed isn't equivalent to what superman releases . Superman would need to eat 100s of suns literally to pull off some of the ridiculous stunts he pulls off like travelling 1000 times faster than light. He doesn't have enough surface area and right shape to absorb light radiation of that magnitude, regardless. There is reason leaves, solar panels... Etc are usually flat .So realism argument doesn't hold weight. Superman would need to look like a giant leaf or satellite or solar panels or something. That too, he would need to be longer surface area than atleast the surface area of the planet.
The only realistic superman is the first one with ability run faster than locomotive, able to lift heavy weights, leap 1/8th mile, durability of tanking at best bursting shell.. Etc. Even that's pushing it. But, the bug explanation of siegel and shuster was pretty good all things considered.Realistically superman would never fly. At best he would be hoping around like an arthropod. His body structure and composition atleast should be internally different.Heck! Having an exoskeleton would be very much in the realm of possibility. Higher gravity can be used for explaining the structural durability of the body. If you want a realistic superman. That's the best you can do. He won't be lifting huge objects without going right through it. Not that, that superman can lift a plane.
Now on to the next powerlevel and mythic storytelling .As if, sun is requirement for blowing up a planet or being that powerful. That's a no brainer. Sun didn't make superman powerful. The explanation was put in to give the illusion of superman's ridiculous feats such as tanking nukes as realistic .
But, it doesn't. It would never make sense because its not meant to be realistic. It's meant to be
mythic like moses parting the sea, krishna lifting a mountain with a finger, jesus walking on water... Etc.
Superman isn't powerful because of the sun explanation. It's because superman became powerful the sun explanation was put in so that people can have crutch for realism . The first thing one punch man does is
make fun of readers who cling to surreal explanations because they want to force something to be not absurd and entirely realistic Or atleast keep the delusion of it.One punch man's power source is this.
People where expecting a grand explanation like gods, aliens, flying donkeys... Etc. But, they got this. Superman doesn't need the sun. He could lift a planet with hundred pushups. If you think that's absurd. Then you shouldn't be reading superman in the first place cause the guy wears a glass for disguise. A guy sneezing away galaxy is never gonna be realistic. It would always be absurd. Superman would always have the absurd in him. He can be strong enough to kill a godzilla and still not be able to kill a mosquito. Anyways, as if Goku needs the sun to destroy a planet. The phoenix force doesn't need it.The hulk powered by toba just smashed an entire multiverse that was supposed to exist after this one.As if, gamma radiation can do that. It's a freaking story. Make stuff up.
Now why do i hate the sun explanation. Well, the narrative makes it seem like human effort or ambition isn't worth anything or That pursuing strength is a waste. That humanity should just be "good". Worse, superman is never questioned for what he is selling as a narrative . As if people read books about weak people's conflicts. As if history books were written by the weak. Even superman with muscles made of hot air needs to be powerful to some degree(it might differ from person to person) for people to find enjoyment in his adventures . Otherwise, what's the point. Sure, many might find fluff, journalism and his office room drama entertaining.But then, what's the need for having a guy that's bullet proof. You can just read about a normal guy clark kent.No need to call the books superman books.Being comfortable with weak state of existence is just pure sloth.I don't care if superman's lifting quintillion tons is just a window dressing. I want a narrative that doesn't encourage sloth and complacency. I want a guy who has to sweat in anyway or form.As it stands, Superman's narrative is only gonna be useful for people who are already strong.