A nebula whose emissions interfere with subspace communications, surveyed by the Enterprise in 2366 while Riker and the Troi women were being abducted from Betazed.
The Gamma Erandi Nebula features in the Next Generation episode Menage a Troi. After a trade conference at Betazed, Picard takes the ship to chart the nebula, leaving Riker and Deanna Troi to enjoy shore leave on the planet with Lwaxana.
The nebula disrupts communications, so the Enterprise learns only on its return that the three have been kidnapped by the Ferengi DaiMon Tog. Riker later manages to hide a message in the static of Tog's ship, imitating the nebula's distinctive interference pattern.
Wesley Crusher, about to leave for his Academy oral examinations aboard the USS Bradbury, recognises the rhythm in the signal and misses his transport to explain it. Picard rewards him with a field promotion to full ensign.