The Supernova hexes are shuffled with the other Outer Sector hexes before building the Outer Sector stack. The Discovery Tile is shuffled with the other Discovery Tiles.
At the beginning of the Cleanup Phase, for each Explored Supernova Sector, roll two yellow dice. Add the value of each Supernova Sector's yellow dice (ignoring blank and hit symbols) to the greatest number of Techs the player Controlling that Supernova Sector has on any Tech Track. If no player Controls the the Supernova Sector, no Technology bonus is added.
If the sum of the die values and Technology bonus is less than the number of the current round, the Supernova Explodes. If this happens; remove all Ships, Structures, Population Cubes, and the Influence Disc (if any) from that Sector and flip it over. Removed Population Cubes are returned to their respective Population Tracks, and the removed Influence Disc is returned to its Influence Track. Exploded Supernova Sectors have no Wormhole Connections to adjacent Sectors but may be Moved to and from with the Wormhole Generator Tech using normal movement rules.
If the sum of the die values and Technology bonus is equal or more than the number of the current round, nothing happens. The Supernova stays stable and a new check is performed at the beginning of the next Round's Cleanup Phase.