Ionian Nebula

The Ionian nebula is approximately 13,000 light years distant from the algae planet. It encompasses a star system with at least two planets.

In their search for the Eye of Jupiter's function and symbolism, Lieutenant Felix Gaeta discovers that a nova occurred in the Ionian system which was seen 4,000 years ago, around the time the Thirteenth Tribe left Kobol.

The existence of the nova at the time of the Thirteenth Tribe's journey and its resemblance to the new nova of the algae planet's system suggests to Gaeta that the Tribe's next marker is the Ionian nebula (Rapture). Galactica and her Fleet begin the journey to this next waypoint to Earth.

As Gaius Baltar's trial begins, the Fleet has almost reached the nebula, despite some fueling delays and the loss of pilot Kara Thrace.

The Fleet is stricken with an abrupt power outage as they enter the vicinity of the nebula, every ship losing power at once. As the ships drift dead in space and without DRADIS, four Cylon baseships also enter the nebula and launch Raiders. Galactica discovers the baseships after partial power restoration, but the Fleet's civilian hardware is slower to restore power and is unable to make an immediate FTL jump. Galactica launches all its Vipers to intercept the Raiders and Admiral Adama authorizes the use of nuclear weapons against the baseships.

Unknown to senior Fleet leadership, four individuals experience mutual musical hallucinations as the Fleet moves closer to the nebula. When the Fleet reached the nebula, the individuals are attracted to meet each other and are able to define the entire song incorporated in the music.

During nebula approach, Laura Roslin, Sharon Agathon and Caprica-Six experience a common dream, taking place at the Opera House, concerning Hera Agathon. On arrival at the nebula, Roslin is dazed or stunned for unknown reasons, although her use of chamalla extract (which, as in past events, has given her prescient visions) may account for this.

Sortied for Cylon incoming, Lee "Apollo" Adama picks up an "unknown" contact on DRADIS and breaks off to intercept it. The unknown bogey leads him on a chase through the dust clouds of the nebula and after outmaneuvering Adama's Viper pulls up along side him. Much to his surprise the "Unknown" contact is actually the supposedly-dead Captain Kara Thrace piloting an unusually pristine Viper Mark II (Crossroads, Part II).

Notes

When an imaginary camera pulls away from the nebula into deep space, it re-enters the galaxy at roughly the same point it exited and zooms to Earth, indicating that Earth and the nebula are not very far apart on a galactic scale.
Ionia was an ancient region of southwestern coastal Anatolia (in present-day Turkey, the region nearest İzmir,) on the Aegean Sea, which was said to be founded by Ion, son of Apollo.