Krypton

Krypton was, before its destruction, the home planet of the Kryptonian race, including Kal-El, the future Superman.

History
Its climate included both temperate regions, where the majority of the population lived, and sub-freezing temperatures at its polar ice caps.Krypton orbited a red star named Rao, which also seemed to be an object of worship for the Kryptonian culture. It shared its solar system with at least one other inhabited planet, Argo, whose inhabitants shared many physiological characteristics with Kryptonians.

Shortly before its destruction, the planet was administered by the Science Council, with the aid of Brainiac, an artificial intelligence with planet-wide oversight and control of Krypton. The planet's government seemed to have been peaceful, though a small military force was maintained for defense against outside enemies. This force attempted to seize control of the planet under the leadership of High General Jax-Ur, but the attempt failed, thanks to the efforts of Jor-El.

Jor-El also conducted geological surveys of the planet's subterranean layers, and concluded that the planet was unstable and on the verge of a catastrophic explosion. The Science Council found his conclusions outlandish, and considered the matter settled when Brainiac discounted Jor-El's findings.

Unknown to the Council, Brainiac had secretly concurred with Jor-El, but had refrained from informing the Council so that it could successfully download its data into a satellite, rather than be tasked to organize an evacuation of the planet. In creating Brainiac, the Council had programmed it too well: the artificial intelligence considered the survival of Krypton's history and knowledge of ultimately more importance than that of its people.

Mere minutes before the planet exploded, Jor-El and his wife, Lara, launched their infant son, Kal-El, into space, bound for Earth. Kal-El would grow up to be known as Superman, one of Earth's greatest heroes.

The shock waves from Krypton's explosion also ravaged the surface of Argo and tore the planet from its orbit, causing it and its inhabitants to slowly freeze over.The explosion culminated in a chemical/geological reaction that imbued the remaining fragments of the planet with a specific radiation level that proved harmful and ultimately fatal to Kryptonians. Several of these fragments found their way to Earth, where they would be known as Kryptonite.

Aftermath of Destruction
Apart from Kal-El, the only known survivors of Krypton's destruction were Jax-Ur and his lieutenant, Mala, both of whom had been imprisoned in the Phantom Zone prior to the planet's destruction. However, because of the Zone's use as a penal dimension, other Kryptonian criminals may have likewise survived.

A more unfortunate legacy than Kal-El/Superman was Brainiac, which installed itself into an android body, in control of a massive warship, and traveled through the galaxy, "fulfilling" its programming by destroying countless worlds after absorbing their history into its library of knowledge. Thanks to the first meeting of Superman and Brainiac, Superman managed to save an Orb containing the history of Krypton and its scientific accomplishments, which he preserved in the Fortress of Solitude.

The inhabitants of Argo likewise died out, with the sole exception of Kara In-Ze, the daughter of the planet's chief physician, Kala In-Ze. Several years after arriving on Earth, Superman traveled back to Krypton's solar system and found no remains of the planet except an asteroid belt of Kryptonite fragments. He followed a faint distress signal to Argo, and managed to revive Kara from cryonic stasis, bringing her back to Earth.

As the sole survivor of Krypton, Superman was sought out by the Preserver, an alien conservationist fixated on saving the last members of endangered species.

Bizarro became so carried away by the idea that he was himself Superman that he tried to re-mold Earth's environment to mimic Krypton's appearance.

Under the influence of the Black Mercy, Superman was trapped in a dream world where Krypton had never exploded, but was forced to "recreate" its explosion when he had to leave and decide for himself that the dream was not real.

Notable Kryptonians

 * Jax-Ur
 * Jor-El
 * Kal-El
 * Lara-El
 * Mala
 * Sul-Van
 * Superman (Justice Lord)

Known Wildlife

 * Shoggoth

Background information
In the earliest versions of Superman comics, the explanation given for his super-strength and speed was that Krypton's gravitational field was much stronger than Earth's, which made its inhabitants constitutionally much hardier than humans.

In his book, The Physics of Superheroes, Professor James Kakalios conducts a series of calculations: if Superman is able to "leap a tall building in a single bound", then, assuming an average-size skyscraper, Superman must be about 15 times stronger than a normal human. He then goes on to explain that, for Krypton to have a gravitational field 15 times stronger than Earth's, the planet would have to either be 15 times larger than Earth or be composed of matter 15 times denser, both of which would be physically impossible. The only way, he concludes, for Krypton to have such a strong gravitational field, would be for the planet to have a piece of high-density dark star matter (similar to the one discovered by The Atom that gave him his superpowers) at its core—which, if that were true, would make the planet's crust so unstable that its explosion was more or less inevitable.