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 13th tribe left Kobol. The nova left behind a gas cloud, known to the Colonials as the Ionian nebula (Rapture).
As Gaius Baltar's trial starts, the Fleet has almost reached the nebula and hopes to find its next clue to the location of Earth (Crossroads, Part I).
When the Fleet jumps into the nebula it is stricken with an abrupt power outage, and every ship in the Fleet loses power at once. As the ships drift dead in space and without DRADIS, four Cylon basestars also jump into the nebula and begin launching Raiders. When power is finally restored to Galactica they discover the basestars. However, the Fleet, having had to completely restart all their systems, is unable to make an immediate FTL jump. Galatica 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 are experiencing mutual musical hallucinations as the Fleet moved closer to the nebula. When the Fleet reached the nebula, the individuals were attracted to meet each other and were able to define the entire song incorporated in the music.
During nebula approach, Laura Roslin, Sharon Agathon and Caprica-Six experiences a common dream where the fate of Hera Agathon appears to be at stake. On arrival at the nebula, Roslin is dazed or stunned for unknown reasons, although the use of chamalla may also be a factor.
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).
The nebula and Earth[edit]
Within the nebula, Starbuck claims she has been to Earth and back, though the technology used for this trip is uncertain. She also claims she can guide the Fleet to Earth from the nebula. If true, this suggest that it is a reasonable number of FTL jumps distant using either Cylon or human technology.
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.