The Pharos siteworld was a planet in the Marrat system, in the Marrat Nebula.

The planet was rich in extremely pure dilithium, so much so that if it were to have been mined it would not have required any form of refinement. This was not discovered until the 2250s when the planet became the location of Starfleet's Project Pharos. The Starfleet scheme involved building a giant galactic lighthouse on the planet, to act as a navigational aid in the dangerous region. It was while digging the foundations for the project that the rich dilithium deposits were discovered.

As the planet was an unclaimed world in a strategically important area space to numerous cultures Starfleet opted to keep the rich dilithium deposits secret, not wanted to make the area a war zone fighting for control of the valuable asset. Never the less the Klingon Kaaj did discover Pharos’ secrets, and in response rallied local criminal elements to attack the nearby Starbase 13, while he took his ship to the planet to attack the construction teams.

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The USS Enterprise arrived in the region to defend Starbase 13, and shortly after made its way to Pharos to investigate the loss of contact with the engineering teams. After a brief confrontation with the Klingons, Captain Pike came upon a unique solution to prevent a possible war with the Klingons. He turned the Enterprise's phasers on Pharos; igniting the vast dilithium deposits and turning the planet into a huge fireball that burnt for decades, and inadvertently created a beacon in the region achieving many of the same goals Project Pharos was aiming for. (EV comic: "The Fires of Pharos")

planets visited by the USS Enterprise (NCC-1701) (2243-2264)
Robert April's command (2243-2251)	Earth • Romulan planetoid • Faramond
Christopher Pike's command (2251-2264)	Earth • GS391 • Areta • Magefferus III • Pharos siteworld • Rigel VII • Talos IV • Darien 224 • Prairie • Neyda Prime • Liria • Jubal • Theta Kalyb • Algol II • Temazi • Corinthia VII • Eridios