 Additional letters, such as "C", "D", etc., may be used for systems with more than two stars.In cases where the binary star has a Bayer designation and is widely separated, it is possible that the members of the pair will be designated with superscripts; an example is Zeta Reticuli, whose components are ζ1 Reticuli and ζ2 Reticuli.Double stars are also designated by an abbreviation giving the discoverer together with an index number.