The Transactions XXVIIIA Reports on Astronomy 2010-2012 provides a comprehensive and authoritative review of what has been achieved in astronomy during the years 2010-12. These insightful and up-to-date reviews from the IAU Divisions and Commissions have been written by the presidents and chairpersons of the IAU scientific bodies. Topics covered in this wide-ranging volume include: fundamental astronomy; the Sun and heliosphere; planetary sciences; stars; variable stars; interstellar matter; the Galactic system; galaxies and the Universe; optical and infrared techniques; radio astronomy; space and high-energy astrophysics; and other IAU activities. The reviews have been written at a level suitable for colleagues in the same fields, but will also be useful for students and researchers wishing to gain an overview of astronomical fields beyond their own research area.

These Transactions provide a record of the formal organisational and administrative proceedings of the IAU XXVII General Assembly which took place in Rio de Janeiro, Brazil. It includes the admission of new members, the Resolutions passed, an account of the regular Business Meetings of the Executive Committee, the Divisions, Commissions and Working Groups, and gives the detailed status of the Membership of the IAU. 2434 registered attendees from 76 nations enjoyed a rich scientific programme of 6 Symposia, 16 Joint Discussions, 10 Special Sessions, and 7 scientific sessions. During the programme over 700 papers were presented and more than 1500 posters displayed. The Proceedings of the Symposia are published in the Proceedings of the IAU Symposia Series, and those of the Invited Discourses, Joint Discussions and Special Sessions will feature in Highlights of Astronomy, Volume 15. Together with those 7 volumes, these Transactions cover the entire General Assembly.