The IAU is composed of the following Members:
- NATIONAL MEMBERS : Organizations representing national professional astronomical communities, desiring to promote their participation in international astronomy and supporting the objective of the Union, may adhere to the Union as National Members. Organizations desiring to join the Union as National Members while developing professional astronomy in the community they represent may do so on an interim basis. They may later become National Members on a permanent basis.
- INDIVIDUAL MEMBERS : Professional scientists whose research is directly relevant to some branch of astronomy are eligible for election as Individual Members. Individual Members are, normally, admitted by the Executive Committee on the proposal of a National Member. Information on the qualification for membership and application procedure can be found here. Individual Members listed in the IAU directory have a valid, public email (so are considered as "voting members" in the IAU database), and are affiliated to at least one Division.
A list of IAU Individual Members per Division, Commission, etc. is available by selecting the desired IAU body ("Science" menu on the IAU home page: Division, Commissions, etc.), and clicking on "Division Members" (etc.). These lists are regularly updated by the Secretariat in the IAU database. A list of the IAU Individual Members per country can be found by first selecting the country in the National Member list, clicking on the country, then on the "Total members" menu appearing at the top of the country page.
The IAU also has Associates:
- ASSOCIATES: The IAU status of "Associate" is offered by invitation exclusively, to individuals who are not IAU members, but are actively involved in the work of the IAU, as members of a Working Group, a Commission, or a Division. The status is temporary and must be reconfirmed at the time of the General Assemblies. Associates are appointed by the Working Group, Commission, or Division with which they are working, according to the IAU Working Rules (Sect XII), and are listed on the IAU web site as "Associates". The list of Associates is available here, and is maintained by the Secretaries of the relevant Divisions in coordination with the IAU Secretariat.
(Updated 06, November 2014)