While Commission 26 remains one of the smallest in the IAU, it maintains an active program which belies its size, as highlighted below. Further information on the commission may be found at our website: http://ad.usno.navy.mil/wds/dsl.html\#iau. This site includes links to other sites and to major databases and catalogues, as well as bibliographies of recent double star papers, an archive of the Commission's Information Circulars, and a list of upcoming meetings.

Commission 21, one of IAU's smallest commissions, consists of some hundred members and consultants working to understand and describe the light of the night sky with emphasis on the diffuse components. Many more work on these topics without being members of the commission. Light is here defined in its broader sense of electromagnetic radiation of any frequency. The diffuse components of the light of the night sky encompass a variety of physical phenomena over the full range of cosmic distance scales and include scattered light, thermal emission, line emission, and any other emission phenomena producing a diffuse light source. These attract interest not only as scientific topics of study in their own right but also as an unwanted foreground or background against which all other sky phenomena are observed. Commission 21 has for mandate to promote research and availability of results on issues related to the diffuse light of the night sky. This document is a report on activities in this field and is not confined to the activities of its members, no distinction is made between work carried out by commission members and non commission members. The report is organized starting with a summary of the state of broad surveys that provide most of the observations. The report on developments in the various disciplines start with the sources closest to the observer known as airglow and progresses by way of the interplanetary and interstellar mediums to the increasingly distant integrated starlight, diffuse galactic light and diffuse emission in other galaxies ending with the extragalactic background radiation.

Commission 34 covers diffuse matter in space on scales ranging from the circumstellar to the galactic and intergalactic. As such it has enormous scope and because of this, it alone forms Division VI. Key aspects include star formation, matter around evolved stars, astrochemistry, nebulae, galactic and intergalactic clouds and the multitude of effects of the interaction of stars with their surroundings. Associated with these areas are a huge range of physical and chemical processes including hydrodynamics and magnetohydrodynamics, radiative processes, molecular physics and chemistry, plasma processes and others too numerous to name. These are complemented by an equally huge range of observational studies using practically all space and ground-based instrumentation at nearly all observable wavelengths. A glance at any data-base of publications over the past few years attests to the vigorous state of these studies. The current membership of the Division is around 800. It also has three separate working groups.

Commission 49 covers research on the solar wind, shocks and particle acceleration, both transient and steady-state, e.g., corotating, structures within the heliosphere, and the termination shock and boundary of the heliosphere. During the last three years there was considerable progress made in studies of solar energetic particles, compositional and other signatures in the heliosphere, solar wind pickup ions, the termination shock, which was finally crossed by a spacecraft, and the boundary between the heliosphere and interstellar medium, and in solar wind modeling and space weather. These topics have been summarized here in five articles, each with extensive references that will guide the reader who wants further details. Observations from the following spacecraft have extensively used during this period: Ulysses, Cassini, Voyager 1 and 2, MESSENGER, ACE, Genesis, SOHO, Wind, and RHESSI.

Our group studies active early-type (OB) stars, with historical focus on classical Be stars, but extending in recent years to include Slowly Pulsating B-stars (SPB), Beta-Cephei stars, the strongly magnetic Bp stars, Luminous Blue Vairiable (LBV) stars, and B[e] stars. An overall goal is to understand the nature, origin, and consequences of this activity, in terms of both the stellar structure and evolution, as well as the distribution and dynamics of circumstellar material and mass outflows.

2002–2005 has seen rapid progress in cosmology with the publication of the 1st year WMAP results and analyses of large scale red-shift surveys, ushering in an era of “precision cosmology”. There has been steady progress, too, in the discovery and study of quasars and galaxies in the early Universe.

There have been three international meetings where the subject area of the meeting was to significant extent within the area of interest of commission 22. These were: The Meteoroids 2004 Conference was held at the University of Western Ontario in London, Canada from August 15 to 21, 2004. This conference was the fifth in a series of meteoroid meetings which have been held approximately every three years since 1992, the previous one being in Kiruna, Sweden in 2001. Ingrid Mann chaired a scientific organizing committee which set the program for the conference. The meeting brought together scientists from more than twenty countries, to deliver 84 oral and 38 poster presentations. The papers represented the research contributions of more than 150 different scientists. The conference provided a comprehensive overview of leading edge research on topics ranging from the dynamics, sources and distribution of meteoroids, their chemistry and their physical processes in the interplanetary medium and the Earthõs atmosphere, and space and laboratory studies of meteorites, micrometeorites and interplanetary dust were also well represented. It was clear from the conference that the coordinated international campaigns for the Leonid showers provided a rich observational dataset and lead to the development of new observational and analysis techniques. Another trend obvious at the conference was the increasing use of sophisticated large aperture radars for meteor studies. High performance computing facilitates both dynamical model calculations and sophisticated ablation models. Significant progress was reported on ablation models for meteoroids ranging from dust to those producing bright fireballs. Study of solid particles entering the solar system from interstellar space and improved dust measuring capabilities on interplanetary spacecraft are an important research area which links astrophysical dust with solar system dust. The majority of papers presented at the conference (a total of 69 papers) are being published as a special issue of the journal Earth, Moon, and Planets (Vol. 95, Nos. 1–4) and also in the form of an associated book published by Springer: Modern Meteor Science: An Interdisciplinary View which was edited by R.Hawkes, I. Mann and P. Brown (ISBN 1-4020-4374-0). The book will be accompanied by a CD-ROM which includes a selection of conference photographs and the complete abstracts of all papers from the conference. As is reflected in the title of the spin-off book, this field is becoming increasingly interdisciplinary in nature, with researchers from astronomy, astrophysics, space science, space engineering, cosmochemistry, atmospheric science and geophysics, as well as others, now contributing to research in the field.

The Supernova Working Group (SNWG) was re-established at the General Assembly in Sidney on July 21, 2003, sponsored by Commissions 28 (Galaxies) and 47 (Cosmology). Here we report on some of its activities since 2003.

The triennial report from Commission 42 covers various topics like massive binaries, contact systems, cataclysmic variables and low-mass binary stars. We try in a number of sections to provide an update on the current status of the main research areas in the field of close binaries. It is not a formal review, even complete or comprehensive, but an attempt to bring the main topics on recent research to astronomers working in other fields. References are also not comprehensive and simply added to the text to help the reader looking for deeper information on the subject. For this reason, we have chosen to include references (sometimes incomplete for ongoing work) not in a list at the end but integrated with the main text body. Complete references and additional sources can be easily obtained through web access of ADS or SIMBAD. Furthermore, the summary of papers on close-binary research contained in the Bibliography of Close Binaries (BCB) can be accessed from the web site of Commission 42. I would like to express the gratitude of the commission for the careful work of Colin Scarfe as Editor-in-Chief of BCB and Andras Holl and Attila Sragli for maintaining the web pages of the Commission within the structure of Division V. Finally, K. Olah and J. Jurcsik are gratefully acknowledged for their continued support as editors of the Information Bulletin on Variable Stars (IBVS), also accessible through the commission web page.

Since the IAU General Assembly in Sydney in July 2003, the WGPSN has conducted its business through numerous e-mail exchanges between the members. A nomenclature workshop was held at Hardingasete, western Norway on September 1–3, 2005. That meeting was attended by eight members from the WG and two from the Task Groups (TG) for the small bodies and for the outer solar system. Input to the meeting had also been received by e-mail from other members.

A meeting of the IAU Working Group on Chemically Peculiar and Related Stars was held in Sydney on July 16th, 2003. The focus of the business session was on possible effects on our WG due to plans for restructuring the IAU. Working Groups are to be evaluated every 3 years and in general, will be limited to a period of 3 or 6 years.

Ihe triennial report from Commission 35 covers its organizational activities and highlights accomplishments in various topics of stellar interior physics.

The Working Group was formed at the request of the Board of DivisionIII and approved by the IAU Executive committee in March 2004. This was in recognition of the fact that discoveries in the Trans Neptunian region were repeatedly raising the question of “what is a planet”. The task of the WG was to investigate the options available and give indications of the level of support and opposition for each if more than one option was emerging.

There have been important advances in radio astronomy in the last three years. New discoveries both at the galactic and extragalactic scale have been reported over this period and we highlight here several of them. The outstanding results of the Wilkinson Microwave Anisotropy Probe satellite, allowing an accurate determination of the main cosmological constants, are certainly among the most important. At the international level, the consolidation of the Atacama Large Millimeter Array project, with participation of the USA, Europe, and Japan and an estimated cost of around one billion US dollars, takes the construction of radio telescopes to a new level of complexity and potential. We also include the Progress Report of the Working Group on Historic Radio Astronomy, that includes a description of the duties and activities of this recently created working group.

Division XI was born by merging Commission 44 “Space and High Energy Astrophysics” and Commission 48 “High Energy Astrophysics” by the decision at the IAU General Assembly in The Hague (1994). As the naming of space astronomy is technique oriented, i.e. astronomy from space, it covers quite a wide range of astronomy, almost all branches of astronomy are included by the progress of space observations. Historically, it started from high energy astronomy, UV, X, and gamma rays astronomy, somewhat including cosmic ray physics. However, in these days, space observations have expanded to low energy astronomy, such as optical, infrared, submillimeter and even radio waves(Space VLBI).

The past triennium has continued to see a huge influx of astrometric positions of small solar system bodies provided by near-Earth object (NEO) surveys. As a result, the size of the orbital databases of all populations of small solar system bodies continues to increase dramatically, and this in turn allows finer and finer analyses of the types of motion in various regions of the orbital elements space.

The WGNEO, a Working Group of Divisions I and III, was formed in the early 1990s to coordinate study of Earth-approaching asteroids and comets (NEOs) and provide timely advice to the General Secretary and officers of the IAU on discovery of any objects that threaten collision with the Earth. Since then, the WGNEO has steadily grown, reflecting increasing international interest and concern over impacts, especially from asteroids (which dominate over comets in their risk to Earth). In this triennium, the WGNEO had a membership of 49 (including the Organizing Committee of 17 members), plus 10 consultants. The Chair is David Morrison (USA), Vice-Chair Andrea Milani (Italy), Secretary Richard Binzel (USA), and Past-Chair Andrea Carusi (Italy).

As documented by the reports of the Presidents of Commission 28 and Commission 47 the fields of extra-galactic research and cosmology have experienced a higher and higher development leading to a vast harvest of results and discoveries. They range from the description of the overall structure of the universe to that of the individual properties of galaxies. The availability of very large telescopes and the coverage of regions of the sky with deep surveys, on the observational side, and the wide use of sophisticated numerical simulations on the theoretical one are starting to produce a satisfactory understanding of the physical processes taking place during the evolution of galaxies. Very often there is an profitable interplay between the subjects of the two Commissions without clearcut boundaries. This makes Division VIII, which is one of the largest of the IAU, counting 1373 members, very well balanced and deserving to remain without modifications for the future.

The Working Group on Extrasolar Planets (hereafter the WGESP) was created at a meeting of the IAU Executive Council in 1999 as a Working Group of IAU Division III and was renewed for three more years at the IAU General Assembly in 2003. The charge of the WGESP is to act as a focal point for international research on extrasolar planets. The membership of the WGESP has remained unchanged for the last three years.

The activities in scientific research related to Commission 19 are mostly developed in the different institutions that have sent their reports here enclosed, in the different meetings that have been organized in related themes, and in the WGs of the Division 1. An important additional activity has been developed in the frame of precession and nutation. This research has been initiated by the Descartes Prize received by the Nutation Consortium in 2003.