Csilla's sun was an Unknown Regions star that was orbited by the Chiss Ascendancy's capital planet Csilla. Around 4300 BBY, the Chiss were forced to use a superweapon known as Starflash to defeat an enemy during a brutal war. The weapon was fired into the sun, which eventually led to a decrease in the star's energy output—a change that, in turn, caused the surface of Csilla to freeze over.
Csilla's sun was a star that was located in the Unknown Regions' Csilla system and was orbited by the Chiss Ascendancy nation's capital planet Csilla, from which it could be seen. It was situated in grid square F-8 of the Standard Galactic Grid.
Stybla family Patriarch Lamiov revealed to Thrawn and Thrass (pictured) the true reason for the cooling of Csilla's sun.
Around 4300 BBY, during a brutal war between the Chiss people and an enemy, the Chiss used a superweapon known as Starflash to fire a massive burst of tachyonic and lightspeed energy into the sun, which triggered a return blast that destroyed the enemy's fleet. However, the burst into the sun caused a disruption in the star's surface layers that extended into its core and eventually caused the sun, and consequently Csilla's surface, to cool. The residents of the Chiss capital were soon forced to move to neighboring worlds in the Ascendancy, while several of the nation's Nine Ruling Families moved their homesteads to caverns beneath Csilla's surface.
Over the next thousands of years, students in Chiss schools were taught about the history of Csilla's sun and the subsequent exodus—although they were not informed of the true number of migrants nor the reason the sun's energy output had changed. At one point between 39 BBY and 19 BBY, Stybla family Patriarch Stybla'mi'ovodo, core name "Lamiov," informed the Mitth family members Mitth'ras'safis "Thrass" and Mitth'raw'nuruodo "Thrawn" of the true history of the Starflash—a secret known only to the Patriarchs of the Nine Ruling Families and their senior aides. He added that the Chiss did not know whether Csilla's sun would ever recover from the effects of the Starflash, noting that he thought it would not.
In the current Star Wars canon, Csilla's sun first appeared in the 2020 novel Thrawn Ascendancy: Chaos Rising, the first installment of Timothy Zahn's Star Wars: The Ascendancy Trilogy. In the Star Wars Legends continuity, an eponymous star that orbited the planet Csilla was mentioned in the 2009 reference book The Essential Atlas, authored by Daniel Wallace and Jason Fry.
- Star Wars: Timelines