Amargosa was the primary star of the Amargosa system. It was studied by a Federation observatory where Dr. Tolian Soran developed a trilithium weapon. In 2371, Soran launched his trilithium weapon into the star, collapsing it and producing a level-12 shockwave that destroyed everything in the system.
The collapse of Amargosa had several consequences, including an increase in gamma emissions. Gravitational forces were also altered, forcing the USS Bozeman to make a minor course correction. The same forces altered the flight path of the Nexus ribbon, bringing it to Veridian III as Soran had planned. (TNG movie: Star Trek Generations)