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|Out of universe information|
- "...P4X 639 was once a colony of the Ancients. They thrived there for thousands of years, until they were struck by some sort of unspecified cataclysm, perhaps a disease, but we'll never really know for sure."
- — Daniel Jackson
The planet is subjected to coronal mass ejections from the planets star causing geomagnetic storms and turbulent atmospheric conditions. The planet has at least one Ancient structure - large ruins where the Stargate is located and the Time loop machine is situated. (SG1: "Window of Opportunity")
The Ancients built an outpost here where they tested their time machine in order to stop the Plague from happening however it did not work so they shut it off and let the end come. In 2000 the archaeologist Malakai had found the planet and discovered what the machine was and attempted to use it to go back in time and see his deceased wife again. SG-1 visited the planet when Malakai tested the device and Colonel Jack O'Neill and Teal'c were caught in the devices field and remembered each loop. They managed to later convince Malakai to deactivate the device. (SG1: "Window of Opportunity")