Planetary Nebulae: An Eye to the Future Proceedings IAU Symposium No. 283, 2011 A. Manchado, L. Stanghellini & D. Sch¨ onberner, eds. c  International Astronomical Union 2012 doi:10.1017/S1743921312010605 Historical overview of planetary nebulae research Sun Kwok Faculty of Science, The University of Hong Kong, Hong Kong, China email: sunkwok@hku.hk Abstract. Planetary nebulae (PNs) were first discovered over 200 years ago and our under- standing of these objects has undergone significant evolution over the years. Developments in astronomical optical spectroscopy and atomic physics have shown that PNe are gaseous objects photoionized by UV radiation from a hot central star. Studies of the kinematics of the neb- ulae coupled with progress in theories of stellar evolution have led to the identification that PNe are evolved stars and progenitors of white dwarfs. Development of infrared and millimeter- wave technology in the 1970s made us realize that there is significant amount of neutral matter (molecules and dust) in PNe. The link of PNe to the stellar winds from their progenitor asymp- totic giant branch (AGB) stars and subsequent dynamical interactions are now believed to be the underlying causes of the morphological structures of PNe. The role of PNe as prolific molec- ular factories producing complex molecules and organic solids has significant implications on the chemical enrichment of the Galaxy. In this paper, we discuss the misconceptions and errors that we have encountered in our jour- ney of understanding the nature of PN. The various detours and dead ends that had happened during our quest to pin down the evolutionary status and causes of nebulae ejection will be discussed. As there are still many unsolved problems in PN research, these lessons of history have much to offer for future progress in this field. Keywords. Binaries: general, planetary nebulae: general, stars: AGB and post AGB, stars: evolution 1. Introduction The study of planetary nebulae (PNe) began with the discovery of the first PN (M27, the Dumbbell Nebula) in 1764 by Charles Messier. The first step towards an under- standing of the physical nature of PNe is the spectroscopic observation of NGC 6543 by William Huggins in 1864, showing that it is a gaseous nebula and is not a collection of stars. In 1922, from an observed correlation between the magnitude of the central star with the size of the nebula, Hubble suggested the the energy of the nebula is derived from the central star (Hubble 1922). With the advances in atomic physics in the early parts of the 20th century, Menzel (1926) applied atomic theories to come to the conclusion that the nebula is ionized by Lyman continuum photons emitted by a hot central star. Zanstra (1927) was able to quantitatively derive the temperature of the central star from the nebular Hβ flux and found out that the central stars of PNe are much hotter than normal stars. The most significant mystery of the unidentified nebular lines (proposed to be due to a new element nebulium) are in fact transitions from metastable states of N + ,O + , and O ++ (Bowen 1928). These discoveries are the result of application of new physics and represents the beginning of the discipline of astrophysics. Planetary nebulae research up to the 1970s can be grouped into three main areas: (i) the discovery of nebulous emission-line objects from imaging (Abell 1966, Perek & Kohoutek 1967) and objective prism surveys (Minkowski 1964, Henize 1967); (ii) The employment 1