Planet in the Milky Way Galaxy 21 light years from Earth, designated P4X-351. The only one of its kind discovered, the Icarus planet possessed a radioactive naquadria core which allowed tremendous amounts of energy to be channeled into practical applications. Stargate Command discovered the planet and, recognizing the world could be used as an immense power source, established Icarus Base as a site to test the nine-symbol Stargate address found in Atlantis's Ancient database.
For two years Dr. Nicholas Rush attempted to formulate the correct balance of power necessary to dial a nine-chevron address. But it was M.I.T. dropout Eli Wallace who succeeded in making the proper equations, and also Eli's suggestion that the nine symbols should conclude with Earth as the point of origin.
The second test of the connection yielded an outgoing wormhole, but not before the planet had fallen prey to a surprise attack by the Lucian Alliance. The exchange of fire on the surface disrupted the core, which obliterated the planet and the attacking ships. Prior to the explosion, the Icarus team escaped with their lives to the Ancient ship Destiny.
HOME TO - Destroyed
FIRST APPEARED - Air, Part 1
Air, Part 1 - The Icarus planet provides the power necessary to dial the ninth chevron to the Ancient ship Destiny only moments before it is destroyed.
Air, Part 2 - Dr. Rush identifies the Icarus planet as P4X-351 [extended scene].
Human - In Rush's memory of the past, Daniel Jackson indicates that they originally found the Icarus planet with the help of a mole inside the Lucian Alliance.