From Bravo Fleet Infobase
Grid A2, Delta Quadrant
21 January 2384
The Solaria Nebula is filled with unusual plasma storms, not unlike those found in the Badlands of the Alpha Quadrant. Because of this, the nebula was used nearly two hundred thousand years ago as a sort of "Iconian Bunker," or last line of defence for the dying race. As such, it is filled with wondrous and hidden mysteries of its own--not to mention enough plasma storms to make flying through it a nightmare.
The Solaria Nebula was discovered by the crew of the U.S.S. Excelsior at the end of the Battle of Union. The first major expedition of the nebula was undertaken by the U.S.S. Tornado during January-April 2384. This expedition, by Admiral Walter Picardo Tenson, was the first to discover a navigable route out of the nebula's plasma storms into open space.
The Nebula was described by Captain Alcar Dovan as appearing something like, "blue and purple and gold flowing together like thick cream in infinitely long streams within the nebula, filling our display with color and blocking out space and all the stars. Exotic particles appeared and disappeared in small nodes of energy at the ends of some of what I can only refer to as 'color-streams.'" This is in Captain Dovan's usual overblown prose, however, and should be taken with a few grains of salt. Stars are generally not visible from planets and stations within the Nebula, or are at least obscured.
At present, there is only one known navigable route out of the Solaria Nebula into open space. Known as the Safe Passage, it was discovered by the U.S.S. Tornado in late April 2384. The Safe Passage is a gap in the static plasma fields, which can be reliably and safely navigated--although large starships (Nebula-class and above) had best go very slowly and very carefully. Accidents can happen, and could well be disastrous.
Depending on plasma storm activity, which varies from day to day, navigation of the Safe Passage can take anywhere from a few hours to more than a week.
Aside from the Tornado survey and the USS Ticonderoga brief jaunt into the Pre-Warp Cradle, no serious expedition into the vast Solaria Nebula storms has been undertaken. More than 99% of the nebula's total area remains uncharted and unexplored.