Division V: Variable Stars

Division V, "Variable Stars", consists of Commission 27, also called "Variable Stars" and Commission 42, "Close Binaries". Thus the former deals with stars whose variations are intrinsic, whereas in the latter the variations are caused by the interactions between the components in the binary. It is evident that the definition of the Division is predominantly observational, and there may be cases where the assignment of an object to one of the two commissions might be in doubt (a recent somewhat related example was the first detection of an extra-solar planet, in 54 Pegasi, where intrinsic variability of the star in the form of high-order g modes was also initially suspected).