Published online by Cambridge University Press: 12 April 2016
The observed rate and spatial distribution of galactic novae can be explained with the concept of two nova populations, the disc novae of faster outburst development, and the slower bulge novae. Similar populations seem to exist in nearby galaxies. The space density of galactic novae depends strongly on the recurrence time, which is unknown and may lie between 500 and 20 000 years. If the recurrence time is long, the population of quiescent novae must be identified; the hibernation scenario may or may not be a solution.