Following a massive atomic explosion on a Tragan Cluster planet close to the moon designated Raspar-6, a strange effect called "irrational echoes" occurred.
The term "irrational echoes" appeared within a single-page weather report called "Region 29: The West Fissure." This report was authored by Bob Carrau and included in the 1993 book Monsters and Aliens from George Lucas. This book is a compilation of concept art and images from several projects by George Lucas. Leland Chee, a Lucasfilm worker who is in charge of the Holocron continuity database, has stated that the book's contents are considered non-canonical.