The planet, presumably named after the chemical element Krypton, was created by Jerry Siegel and Joe Shuster for the syndicated daily newspaper strip in 1939 and later brought into the comic books. Krypton no longer exists in the DC Comics universe, as it exploded as a result of highly unstable geological conditions. The entire civilization and race of Krypton perished in the explosion, except for one sole survivor: the baby Kal-El, who was placed in an escape rocket by his father Jor-El and sent to the planet Earth.
There have been two versions of Krypton (so far) in the history of Superman. The first version developed gradually over the course of nearly fifty years of Superman adventures in comic books, radio, TV, and written stories. Originally, Krypton was an idyllic world in another part of the universe, which had given birth to a race of "supermen." The first fictional portrayals of Krypton depicted all inhabitants of the planet as having super powers similar to what Superman originally had in the 1940s. In fact, the first telling of Superman's origin shows the scientist Jor-L (before he was renamed Jor-El) racing through the streets of Krypton at super-speed, and making a gigantic leap through the air to reach the balcony of his home. Over time, the status of the inhabitants of Krypton was changed, largely to answer the question of why the entire population perished when the planet exploded, if they could have used their super powers to simply fly away and find a new world to live.
The idea of Superman's powers being given to him by a "yellow sun" and negated by a "red sun" came from this retroactive explanation of the limitations of the powers of Kryptonians (as the inhabitants of Krypton were known).
Krypton (now generally known as "Old Krypton" by Superman's fans and comic book historians) was a super-advanced paradise where science ruled above all. Through the use of science, Kryptonians had freed themselves from all worries, cares, chores, and wars. Robots and computers were used for everything on Krypton, even for determining what career paths the young boys and girls of Krypton would take as they grew up. One Superman story from the 1950s, What if Krypton had not exploded?, depicted life in a setting that epitomized the cliche of the "future" as seen in science fiction stories of the time. Superman also travelled in time to Krypton's past before it exploded in the story Superman's Return to Krypton, where he fell in love with a Kryptonian lass named Lyra Lerrol. In the 1980s, writer Alan Moore also gave a glimpse into the world of Krypton in his story For The Man Who Has Everything.
There were two great cities on Krypton: Kandor and Kryptonopolis. The city of Kandor was the capital of Krypton, but when it was shrunk by the evil super-computer Brainiac and taken away, Kryptonopolis became the capital.
There were many strange animals and plants on Krypton, including such incredible species as a giant mole that could eat through metal. Many of these beasts lived in a wild area of the planet called the Scarlet Jungle. Such landmarks as a "Gold Volcano" and the "Jewel Mountains" were the sources of the various forms of Kryptonite, created in the planet's explosion.
Krypton had two moons, but one of them was accidentally destroyed by the Kryptonian scientist Quex-Ul when he was experimenting with space travel. The disaster killed millions of inhabitants of the moon, and because of this Quex-Ul became the first criminal to be banished to the Phantom Zone, which had been discovered by Jor-El. This disaster also prompted the Science Council of Krypton to ban space flight completely, providing another explanation of why Krypton's civilization perished with the planet.
When the planet exploded, one entire city of Krypton survived the cataclysm. This city, named Argo City, drifted through space on an asteroid-sized fragment of Krypton, which had been transformed into Kryptonite by the explosion. The super-advanced technology of its Kryptonian inhabitants gave the denizens of Argo City the ability to construct a life-sustaining dome that allowed them to survive for several years, in addition to building a lead shield that protected their city from the Kryptonite radiation of their asteroid. However, the protective shield was destroyed in a meteor storm, exposing the inhabitants to the deadly radiation. One sole survivor of Argo City, Kara Zor-El, was sent to Earth by her scientist father to live with Superman. Kara adjusted to her new life on Earth and became known as Supergirl.
In his first encounter with Brainiac, Superman discovered the city of Kandor preserved in a bottle. He rescued it and took it to Earth with him, vowing to someday discover a way to return the city to normal size. In the early 1980s Kandor was enlarged, and its inhabitants left Earth to settle on a new planet which was named New Krypton.
The race of Krypton was believed to be the progenitor of the alien world of Daxam, a planet whose inhabitants also had powers and abilities similar to Superman's when they were exposed to the radiation of a yellow sun. However, the Daxamites as they were known, were highly suspectible to lead poisoning, which affected them in a manner similar to Kryptonite when they came into contact with lead. One Daxamite, Mon-El, was a member of the Legion of Super-Heroes in the 30th Century of the DC Universe. While suspected, a direct link between the inhabitants of Daxam and Krypton was never proved.
Much of the history of Krypton was rewritten beginning with the Man of Steel miniseries in 1986 by John Byrne. The revised, retconned history of Krypton is summarized as follows:
Krypton was approximately the size of Earth though it orbited a red sun which may be a red giant star. Located fifty light-years from Earth, Krypton maintained an isolationist stance forbidding interstellar travel until its destruction.
Over 100,000 years ago Krypton had already developed scientific advancements far beyond that of present-day Earth. Kryptonians had conquered disease, learnt to retard the aging process and perfected cloning making their population virtually immortal. They kept vast banks of non-sentient clones of themselves to replace body parts in the case of injury or accidents. A political movement demanding rights for the clones kept in these organ banks broke out into full scale hostility known as the Clone Wars. A terrorist faction known as Black Zero caused the reigning Kryptonian government considerable strife and as a result of the devastating war the clone banks were abolished and Kryptonians turned to other means of prolonging life.
In direct contrast to the idyllic and sensual society that had existed prior to the Clone Wars a sterile and spiritually dead civilization emerged. The population became isolated from one another with personal contact shunned. Procreation became a matter of selecting compatible genetic material which would then be placed within a birthing matrix. Interstellar travel was forbidden as was any attempt to contact other worlds. It was into this world that the young scientist Jor-El was born. He discovered that the planet's core was unstable, transforming into a dangerously radioactive substance which is known as K-radiation. This is the radation that Kryptonite emits. Due to this transformation the planet itself was going to explode. Jor-El attached rockets to the birthing matrix of his unborn son Kal-El and sent him from Krypton to Earth.
Although a few fragments of Kryptonian technology survived the destruction of the planet, no other members of the Kryptonian race are currently known to have survived the planet's destruction in the post-Crisis DC Universe. The supervillain Doomsday is known to be of Kryptonian origin, though he was apparently created hundreds of thousands of years before the rise of Krypton's civilization.
It has also been established in the comics that Krypton still exists as a gaseous planet similar to Saturn formed when the remaining material, which was still of a sufficient amount to create gravity came back together partially.
"Old Krypton"
Modern Krypton