The IAU has as its task (Statute 1):

1. (a) to develop astronomy through international cooperation;

2. (b) to promote the study and development of astronomy in all aspects;

3. (c) to further and safeguard the interests of astronomy.

The Union to carry out its mandate is organized into 11 Divisions representing major branches of astronomical activity. The Divisions are composed of specialist Commissions -out of 39 Commissions, 31 operate within the divisional structure: of the 8 Commissions which do not, 6 may be regarded as representing “Services”. Additionally there are 4 Working Groups of the Executive Committee. Table 1 lists the Divisions and their constituent Commissions.