Inversion nebula

An inversion nebula was a type of nebula composed of unstable plasma strands. These strands would ignite, starting a chain reaction that burned out the nebula in only a few years. 

History
Marayna's nebula was a centuries old inversion nebula inside the Nekrit Expanse in the galaxy's Delta Quadrant. This nebula was artificially prevented from burning out with the help of a dampening field projected from a cloaked space station operated by Marayna. 

As of 2371, no inversion nebula had been observed in the Alpha Quadrant but Federation scientists had inferred their existence based on theories. In the year 2373, on stardate 40460.3, the Federation starship USS Voyager visited Marayna's nebula and found the unusual dampening field preventing the nebula's plasma strands from igniting the inversion nebula in a chain reaction.