10,000 km (diameter)
Unusual spatial phenomenon in star system MW-DQ-T2-V002-LRS21599, also known as Spatial Disturbance One, the Trippy Vortex, and simply The Impossibility. First noticed during an Excelsior flyby in October 2384, the Impossibility emits all manner of unusual particles not normally detected in nature, and Chief Science Officer J'naya was initially optimistic that study of the vortex (described in X.O. Alecz Lorhrok's report as "trippy") could revolutionize physics. It has since become the focus of a large, specially assigned Federation task group, as the Impossibility's unexplained expansion threatens surrounding space and--perhaps--the fundamental structure of space-time.
The Impossibility appears, according to reports, as a "dancing, blue-purple light, sending off flashes and tendrils of energetic particles along an axis," roughly ten thousand kilometers in diameter and slowly expanding. It is all but impervious to scans due to its reluctance to give back readings that make any sense, but telepathic probes have proven somewhat effective in exploring it.
Stellar System: DQ-T2-V002-LRS21599
The barely-charted Round Table star system that contains the Impossibility consists of five planets. Two are gas giants, two are tiny and molten, and one is nestled comfortably in a habitable zone around the yellow star.