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Recently in the CW series Supergirl, title hero Kara Danvers (played by Melissa Benoist) lost her powers while exposed to the radiation of a red sun. So it seems timely to delve into just what the power sources is for Supergirl, her cousin Superman, and other Kryptonians that inhabit the DC Comics universe.


A major inspiration in the creation of Superman was the character John Carter, Warlord of Mars. Created by Edgar Rice Burroughs, John Carter is a human being who winds up on the planet Mars (known to its inhabitants as Barsoom) and gains great strength, speed and agility due to the planet’s lesser mass and gravity. Jerry Siegel and Joe Shuster decided their character Superman would be the reverse of this: an alien who comes to Earth and has his abilities enhanced by its environment. Along with this, Siegel and Shuster imagined that their hero came from a race that was similar to humanity but far more evolved, both intellectually and physically, a “race of supermen” who were naturally stronger and more agile.

However, when Superman debuted in Action Comics #1, his origin and premise had to be explained in just one page. So on that opening page, we aren’t told about Earth’s gravity and mass in comparison to Krypton’s. We’re just told that Superman is from a race of beings biologically superior to Earth people. Since a major criticism Siegel and Shuster got during many rejections was that Superman seemed too unrealistic, the opening page of Action Comics #1 also remarks to the reader that the hero’s powers may not seem outlandish if you consider that creatures on Earth itself have evolved to carry many times their own weight and leap proportionately great distances.

By the next year, Superman was now a hit sensation. In the comic books, Siegel and Shuster now introduced Earth’s weaker gravity and mass as a major contributing factor to his physical prowess. The fact that his people were biologically superior accounted for his heightened senses and brain power. Of course, eventually, Superman was able to not only leap over tall buildings but actually defy gravity itself and fly through the air. But no explanation was given for this ability until many years later during…


In 1956, DC Comics started rebooting many superheroes whose adventures hadn’t been published in years, starting with the Flash. This started the Silver Age of comics. By 1958, Superman was rebooted as well, with new high-concept science fiction elements added to his mythos. During a retelling of his origin, it was now established that his powers came partially from genetics and Earth’s weaker gravity/mass, but most of all from his alien cells being able to absorb and process the radiation of Earth’s sun, a younger yellow-colored star as opposed to Krypton’s old, dimmer red star Rao (or Eldirao).

This added to Superman’s symbolic quality, making him akin to a primal sun-god of the DC Universe. It also now gave him new weaknesses and cemented how old ones worked. Kryptonite, which had been around for a while, was now said to be radioactive and poisoned his cells, replacing the healthy solar energy with its own. Certain radiations and energies (such as magic) disrupted the solar energy in his cells, leading to injury or pain. And journeying to an environment where there was no solar radiation or where the solar radiation was too weak, such as a planet lit by a red sun, meant he lost his powers once his batteries got low.

Along with all this, certain enemies were now able to simulate the radiation of a red sun with weapons and jail cells. By firing red sun radiation at high intensity at Superman, his cells absorbed it and seems to push out the yellow sun energy in the process, making him instantly more like a human being.

Starting in the 1990s, Superman’s heat-vision was now said to be a direct release of the solar radiation in his cells. That means that the more he uses heat-vision, especially if it’s high-intensity, the faster he starts depleting his energy reserves. In season one of Supergirl, Kara uses her heat-vision and full blast repeatedly during a few days when she is fighting her hardest against an android enemy. As a result, she loses her powers and is essentially human for a day.

Of course, in reality, science tells us there is very little difference in the radiation released by a red sun and a yellow sun. But it’s comics, folks. Enjoy the stories of the hero in capes!