dead zone

A dead zone within a circumstellar disk is a type of region with low gas viscosity, which are presumed to reduce planetary-migration effects within the area. Extra-solar planet studies suggest some discovered planets have migrated, and some mechanisms that have been worked out to explain this would seem to migrate all developing planets into the host star. Given this, model-features have been explored that would allow developing planets to avoid such migration. Gas viscosity of the disk underlies theorized planet-migration models, and to explain why some planets survive beyond the life of the disk, the possibility of regions within the disk that have less than the usual viscosity have been explored.