The Lion's Head Nebula, according to the Scroll of Pythia, was a navigational waypoint to Earth by the caravan of the Thirteenth Tribe. The scripture reads:
And the caravan of the heavens was watched over by a great lion with a mighty blinking eye.
The nebula's perceived "eye" is a system of red and blue eclipsing binary pulsars appearing to align to the scripture's description.
Following the Second Exodus, the Cylons investigate the nebula when Gaius Baltar tells them it might contain a clue to the location of Earth. A basestar sent to investigate finds a beacon possibly left by the Thirteenth Tribe. When the beacon is brought on board, a disease it carries kills most humanoid Cylons, and affects the biological components of the basestar and Hybrid, resulting in deterioration of the assets and systems it controls, including the Raiders and Centurions onboard.
Independently on Galactica, Lieutenant Felix Gaeta analyzes Baltar's research and briefs President Laura Roslin and Admiral William Adama on the nebula. A Raptor, manned by Margaret "Racetrack" Edmondson and Athena, discovers the nebula and the graveyard of drifting Cylon spacecraft (TRS: "Torn").