The Exodus

Due to the downfall of Earth, humanity was forced into an immediate and complete evacuation of the planet.

The First Gate
While Jump Gate technology had existed for several decades, it was considered too expensive and unreliable for wide-spread use, as no test ships had ever made contact post-jump.When the technology was still being developed, a few S.U.N. ships staffed with volunteers had been send out and were never heard from again.

With the sudden demise of Earth looming, humanity turned to the recently uncovered Jump technology with desperation. Any spacefaring vessel capable of maintaining a stabilisation field was gathered up into a colossal fleet, and with a massive burst of energy the Earth Gate was torn wide enough for a single, combined jump. Although the strain caused the Earth Gate to collapse, seemingly sealing off what was left of Earth forever, the fleet successfully arived in a new, uninhabited system.

As a relatively small proportion of Earth's vessels were able to make the jump, those unable to follow the Exodus began their own Exodus to the partially terraformed Mars, though the eventual fate of this expedition is unknown.

Pyrian Space: Fool's Gold
The barren system the fleet found themselves in soon proved to be no great improvement on Earth. With the two suitable planets in the system only barely suitable for terraforming, and resources in even greater scarcity than before the voyage, tensions were high and showed no signs of fading.

One group, realising that the new system held little hope of civilisation, led a large group of ships in leaving the system via Warp drive, leaving the Gate behind, in the hopes of finding a different planet. As a result of the near-total speeds used in Warp, time dilation resulted in many, many years passing before this group found a habitable planet. For more, see: (Shield of Kytettee)

The remaining refugees split into several groups:

There were those that thought they could make it in the nearby star system. They settled on the most-habitable planet, that though similar in gravity and temperature, had a thin, toxic atmosphere. And while the early years were very hard on them, they managed to set up a stable colony. It was this group of oppertunists that named their territory after pyrite, the fool's gold, and it became known as Pyrian Space.

At the same time, there were those with great faith that building another Jump Gate would bring them to a promised land. With almost religious zeal, they united their resources and efforts into building second Gate. This collective finished their project in record time, but had run very low on resources due to a lack of support from the Pyrian colonists. Nevertheless, the collective left through the gate on a search for their promised land. It would be many, many years before they're able to re-establish contact with Pyrian Space.