The Mutara Nebula
The term Mutara-class nebula refers to any nebula with similar properties to the Mutara Nebula.
In 2374, the USS Voyager came upon a radioactive Mutara-class nebula. The nebula emitted subnucleonic radiation which greatly affected humanoid skin. The nebula was about 110 light years long and would take one month to travel through. The Voyager crew (except The Doctor and Seven of Nine) were put in stasis pods for the duration of the trip. During the trip, the ship suffered many problems due to the radiation including gel pack randomization problems and computer errors. (VOY: One)