The Sun Device was apparently built by the Precursors to function as an artificial radiation source for cold planets. Containing an amazingly powerful exotic energy generator, the Sun Device is a relatively small apparatus that can produce 0.001 percent or so of the Sun's total radiation; this object can be placed in low orbit around a planet, meaning almost all of the radiated energy will be absorbed by the planet. This is a huge amount of energy to add to a planet at once, equivalent to giving the planet a new, artificial sun.
This unique artifact was safeguarded by the Mycon for a very long time (most recently at Beta Brahe); whether it was intended for their use originally or merely found and used by them is unclear, but it was a very important tool in the Mycon's expansion, allowing them to augment the temperature of planets that would otherwise simply be too far from their stars to provide the heat in which the Mycon thrive. The Mycon thus treat the Sun Device as a holy object, calling it the "pod of Juffo-Wup," and guard it zealously. By working with the Syreen to lure most of the Mycon fleet into a trap, The Captain is able to overpower the guards at the Sun Device's world and steal it, knowing that it is the only object capable of accelerating the Process of hybridization between the Chenjesu and Mmrnmhrm.
Sources of information
The proto-Chmmr state that The Process is driven by radiant energy (light). Although they do admit that larger amounts of light might speed up the process, they warn that it could be dangerous.
What the player has to do
The Sun Device is essential to completing the game. In order to be able to land on the planet to retrieve the device, the bulk of the Mycon fleet must be sent into the Syreen ambush at Organon.
Using the Device while in orbit of Procyon II accelerates the hybridization and causes the Chmmr to emerge.