Mergers of stars may explain the production of numerous exotic astronomical objects and events. In addition, near-mergers of stars are strongly believed to be crucial in forming several of the highest-profile classes of stellar system in astrophysics. This near-merger process is called "common-envelope evolution" (CEE) and involves two stars temporarily merging before the envelope of one or both of them is ejected. Sadly our physical understanding of mergers and CEE has only developed slowly, and the observational evidence has mostly remained very indirect. I will give examples of the importance of stellar mergers and CEE, and illustrate where reliance on simplified pictures rather than physical understanding may well have been misleading. I will also explain how, somewhat unexpectedly, near-future direct observations should be revolutionary for the field.

Bio: Stephen Justham works in the National Astronomical Observatories of the Chinese Academy of Science. Following an undergraduate physics education in Cambridge, he completed a PhD at the Open University, then enjoyed time as a postdoc in Oxford before coming to China, first at KIAA and now NAOC. Stephen has mainly worked on topics relating to compact binary formation and supernovae.