Activities in the various astronomical sub-discplines are mostly coordinated through the 11 IAU Scientific Divisions. These Divisions act as umbrellas for one or more IAU Commissions, each focusing on a narrower scientific or organisational theme.
Currently, the IAU Scientific Divisions are the following:
A table, listing the number of members in the Divisions and Commissions of the IAU, is given here.
For contact information to the Commissions, please consult the Complete List of Commissions and Their Links, or the List of Addresses of Commission Presidents, Vice-Presidents, and Division Affiliations.
A few Commissions have been given the charge by the Executive Committee to oversee matters related to the health of astronomy worldwide - Commissions of the Executive Committee - or cover subjects ranging across all astronomical disciplines. These Commissions are not included in the above structure of Scientific Divisions.
Finally, Working Groups have been established by the Executive Committee, by Divisions, or by Commissions, to undertake certain well-defined tasks for certain periods. Among these, the Working Groups of the Executive Committee undertake essential functions on behalf of the IAU as a whole.