TL-9139 was a star with an associated star system in the Tellar sector of the galaxy's Alpha Quadrant. In the 23rd century, it was the site of a Starfleet-operated Federation shipyard. (STO - Age of Discovery short story: "Utopia Planetia: The Mystery of Yard 39")
History and specifications
The star was the site of Yard 39. In the year 2259, several Starfleet ships operating with Kurtzman-Beyer warp drives were docked at the shipyard when a freak eruption flooded the system with baryon radiation. Starfleet abandoned Yard 39 and the starship hulks. Subsequently, the system was deemed too hazardous for travel. A pulsing green cloud expanded from TL-9139, and a navigation clearance zone of 0.5 light-years was established. This also led Starfleet to phase the Kurtzman-Beyer drive out in favor of the established Cochrane-Archer assembly.
150 years later, in 2410, the eruption was abating, and the system would be visitable a few weeks after the launch of the USS Narendra. The staff of the Utopia Planitia Fleet Yards became interested in recovering the abandoned ship hulks at Yard 39. (STO - Age of Discovery short story: "Utopia Planetia: The Mystery of Yard 39")
Starfleet revisited the system, recovered the hulks and returned the phased-out classes to service. Brand-new ship classes were based on the Burnham's War-era designs as well, including the Europa-class. (STO - Age of Discovery short story: "Utopia Planetia: The Mystery of Yard 39", STO video game: Age of Discovery website: "The Stats of the Europa Class!")
Starfleet Command directed considerable resources into the TL-9139 system and facilities. Other powers of the Alpha Quadrant Alliance and shipyards contributed to revive further 23rd-century ship classes. This was reported on stardate 87831.2 in an article by the Jayce's Interstellar newsfeed. (STO - Mirror of Discovery short story: "Jayce's Interstellar: Around the Galaxy")