From the introduction:
A little over two years ago, the Earth was destroyed in a clash between the Ganglion and the Ghost. Whether they were coming for humanity is unknown, but after the ark ships made their escape, the Ganglion began to hunt them down. One ship, the White Whale, containing the city of New Los Angeles, crash landed after an attack.
The planet showed up out of nowhere. It wasn't on any sensors, it wasn’t within visible range. One minute it wasn’t there, and the next the White Whale was crashing into it.
Welcome to the planet Mira.