Sigma Hydra system

The Sigma Hydra system was an unclaimed and uninhabited binary star system located between Klingon and Federation space. (Star Trek Online: Valkyries)

In late 2405, the binary stars at the heart of the system began to merge, causing gravitational distortions and plasma storms across much of the system. The storm activity restricted travel through the system and ravaged the atmosphere of the ninth planet, turning it into a Class Y planet.

During this same year the system was the site of a skirmish between Starfleet, Klingon, and Orion Syndicate forces over the fate of Orion defector Naisa D'falas, whose shuttle had crashed in the system. ("Airborne")