Kal-El/Superman has been sent to Earth by his parents to protect him from Krypton's destrucion. On Earth, he develops superpowers and become the Eath's protector. Kryptonians don't have superpowers on her native world (Krypton would be a complete mess otherwise). This is explained by the fact that radiations affect Kryptonians; in particular, our yellow Sun is the source of Superman's powers whereas Krypton's red sun has no effect on Kryptonians.

In the recently leaked pilot of the new TV show Supergirl, Kara Zor-El, Kal-El's cousin, is sent to Earth by her mother with the explicit mission of

protecting her cousin, at that time a baby. She explicitly tells Kara that she will have super-powers on the Earth due to the yellow Sun.

In the comics, do Kryptonians know about the effects that yellow suns have on them? Do they use this information in any way (building an empire of yellow sun powered planets for example)?

Note that, although my question originated from it, I am not interested about answers about Supergirl TV show (I want to see how the show will develop its own storyline), but from comics answers. Informations about Man of Steel and the DC movieverse would be a nice bonus.

  • 3
    Russel Crowe seemed to know
    – calccrypto
    May 29, 2015 at 13:32
  • @calccrypto So did Brando May 29, 2015 at 15:07
  • 2
    It was in the original superman movie: his mother did not like the idea that he would be so strange and have super-powers due to the yellow sun. May 29, 2015 at 16:05
  • @MichaelItzoe Darn. Forgot about that. It's been too long.
    – calccrypto
    May 29, 2015 at 22:51
  • @calccrypto: thank you. I was reluctant to the idea of watching the beginning of the movie again. I just have thought of the trailer.
    – Taladris
    May 30, 2015 at 2:17

3 Answers 3


Various versions of the El family, at least, have been aware of the effects of yellow sun light on Kryptonian physiology. As for taking advantage of it, most versions of Krypton in Jor-El's time have no means of doing so. Kal-El's and Kara Zor-El's craft are usually prototypes; most versions of Krypton at the time of its destruction are only just discovering or re-discovering interstellar travel.

The denizens of some versions of Krytpon have a biological attachment to the planet which prevents them from leaving; in these, overcoming this attachment is Jor-El's major advance.

Some versions have a long-lost age of space exploration; however the greatest impact of this travel is the dispersion of the occasional artifact or interbreeding with the indigenous population of the odd planet.

In the New Krypton storyline, the bottle city of Kandor was restored in Earth's solar orbit, on the other size of the sun. While Earth orbit may simply have been the most convenient choice at the time, knowlege of the effects of yellow sunlight seem to have quashed any thoughts of relocation.

In the many limited variations of the Superman story related through "imaginary", what-if, Elseworlds, etc stories, Kryptonians have come to Earth with plans beyond survival. An El ancestor comes to Earth in the 18th Century and assumes the throne of (an invincible) British Empire. Several stories have had members of Jor-El's generation arriving on Earth with plans ranging from benevolent meddling through conquest.

  • Nice answer. I was not sure about Krypton's capabilities in terms of space travel.
    – Taladris
    May 30, 2015 at 2:16

Like most elements of Superman, this depends on the version you are speaking of [Golden Age, Silver Age, Bronze Age, and Modern Age; further to that, we have Post-Crisis, New 52 and Rebirth.] Various media would portray Kryptonians extent to the knowledge as anywhere from Common place to theoretical. I'll try to find some initial examples, then modify it later when I have more time. To save time, we can broadly categorize these into Pre-Crisis and Post-Crisis examples.

Pre-Crisis Roughly from Superman's origin in 1938 to the early 50s, writers were still working out the details and extent of his abilities; this is partially why in many of hose stories you'd see him develop some odd new power "on the fly", the other being that it was comics "Golden Age" when stories were more light-hearted and heavily influenced by the George Orwell sci-fi aesthetic of the time. It is generally given that Kryptonians at this time more or less knew they were a "planet of highly evolved Supermen!" This could be seen in the recreation of superman's Golden Age Origin story, seen here....

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As wasn't uncommon at the time, the Kryptonians seemed to have some limited abilities, even on their own planet. Jor-El at least knew that on a gravitationally lighter world, those abilities would be even further increased. Gravity however, and a more evolved structure, were the the very basis of these fantastic feats they pulled; sunlight seemed to have little to do with it, in story.

Later, in the 40s and 50s as his powers began to grow, a new explanation was needed; Gravity-based abilities would have him jumping far and extra strong, yes, but it wouldn't account for super senses, X-Ray vision or ice breath. So they changed it to the yellow rays of the sun giving him the majority of his abilities, and adding to his gravity and evolution based aspects, making him even stronger. This can be seen even in a 1960s comic, here, where Superman obviously new the effects it would have:

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Here, from a mid 70s comic, is an example of Kryptonian scientists of indistinct era knowing the effects Earth's environment would have on them:

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Now to be fair, these are all Pre-Crisis examples. I was looking for one other that spoke to how scientists on Krypton in the George Reeves Adventures of Superman show both knew that they were "superior" to other men naturally, and that "earth's atmosphere" would enhance these abilities. Unfortunately, that web comic, Panic in the Sky, seems to have been removed. So moving on to 1986's Jon Byrne reboot---- the definitive marker for Post-Crisis Superman, which more or less informs the modern era---- we have an example of Jor-El, from issue 1 of Man of Steel, showing full knowledge of what the yellow sun would do to his child.

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This more or less is shown as canonical; most Post-Crisis versions, from the DCAU Superman:TAS to Smallville to the Man of Steel movie all show Jor-El speaking on the differences in the planets and what affect that will have on Kal-El's body. Here's a scan from the 2010 comic Secret Origin which shows a recording of Jor-El explaining this to the boy in his early teens.

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It was a major plot point in the 9th season of Smallville; when a number of Kryptonian "Replicant" clones are released from a Kandorian orb, they are initially without there powers. A series of flashbacks explain how their powers were nullified; they were mostly soldiers, lead by Major Zod. Zod recalls to his troops how twenty years before the destruction of Krypton, the Ruling Council took their blood shortly before the destruction of Kandor, which is what was used to clone each of them on Earth. Just as Clark realizes that the clone of his father is on Earth while investigating a Kandorian landing in the desert, Jor-El arrives at the Kent Farm. Again, Jor is a scientist, so his knowledge would naturally be greater than others, but it is implied at least that this was commonly know. You can see a small clip of it here:

In the flashbacks shown, it is made explicitly clear that when the council tasked him with creating the Orb, Jor-El forewarned the council that releasing Kryptonians on earth would empower them, putting the humans at risk of subjugation. To combat this, Jor-El treated the orb with Blue Kryptonite [which, in this world, nullifies all Kryptonian powers under a yellow sun without killing them]. When his soldiers awoke, they outright asked Zod why they didn't have their abilities, and most of the season is built around their attempts to harness the sun and whatever technology they can to gain those abilities.

A final example would come from 2004's Superman: Birthright in which Jor-el, again, alludes to the effects a yellow sun would have on a Kryptonian cellular structure. Again, while him being a scientist may give Jor-el more insight,it is not implicitly stated this was the case.

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So while possibly not super prevalent, I think it's fairly common knowledge amongst the Kryptonian people that they are more advanced than other humanoid races. I think the extent of their powers under a yellow sun is something only those who are in the fields of science, development, space travel or other scholarly arts may be something they have a clear idea of.


In many versions of Superman, Kryptonians are an interstellar race, having several colonies. This is why Kara Zor-El and her family survive Krypton's destruction, because they are living on a colony world. So, Kryptonians likely do know the effects of Yellow sunlight, with any colonists living in star systems with yellow or blue suns developing powers. And, in many versions, Lara (Superman's birth mother) mentions that he won't fit in with humans, and will have powers and abilities. In Man of Steel, Jor-El replies to this, saying that he will "be a god to them", referring to humans. So his parents at least knew about the effects of the yellow sun.

In Man of Steel, it seems most of the colonies rely on Krypton for regular supplies, and are not self sufficient, seeing as when Zod and his soldiers arrive, they are all destroyed, and everoyne is dead.

In some versions of Supergirl, her parents send her to earth to avoid death. In the original version of Supergirl, they do not live on a colony, but on a peice of Krpton that survived the explosion, in a major Kryptonian city called Argo, and she is sent to earth because Argo drifts into a yellow sun's range, and turns into a giant peice of green kryptonite, and begins to kill everyone. In later versions, her family live on a colony, which begins to fail following krypton's destruction, and is sent to earth, again, because her parents know they are going to die. In every version, she is sent to earth because her parents know Kal-El was sent there, and will take care of her.

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