Introductory remarks

Observations of extragalactic novae date back to the early twentieth century, and were influential in the debate concerning the nature of the spiral nebulae (see van den Bergh (1988) for a review of the early history). Initially, the identification of extragalactic novae was fraught with confusion, as the distinction between classical novae, with typical absolute magnitudes ranging from Mpg ∼ -7 to Mpg ∼ -9, and supernovae, which are of order ten thousand times more luminous, was not yet appreciated. The best-known example of this confusion concerns the report by Hartwig (1885) of a ‘nova’ in the great nebula in Andromeda. This object, S And, is now recognized as the first and only supernova to be observed in M31. Just a decade later another bright star was discovered very near the spiral nebula NGC 5253 by Fleming during her examination of Draper Memorial photographs (Pickering & Fleming, 1896). This object, Z Cen, is also now recognized as a supernova (SN 1895B). No additional nova candidates were associated with spiral nebulae until the discovery on 19 July 1917 by Ritchey (1917a) of a 14th-magnitude transient star in the outer portion of NGC 6946. This discovery set off a systematic search of archival plates from the Mt Wilson 1.5 m reflector dating back to 1908.