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The meeting was opened by Ted Bowell, president, at 11 am. The 2006 Division III meetings were reviewed by Guy Consolmagno, secretary; as the minutes of those meetings have already been published, they were assumed to be approved.
Commission 53 on Extrasolar Planets was created at the 2006 Prague General Assembly of the IAU, in recognition of the outburst of astronomical progress in the field of extrasolar planet discovery, characterization, and theoretical work that has occurred since the discovery of the pulsar planets in 1992 and the discovery of the first planet in orbit around a solar-type star in 1995. Commission 53 is the logical successor to the IAU Working Group on Extrasolar Planets WG-ESP, which ended its six years of existence in August 2006. The founding president of Commission 53 is Michael Mayor, in honor of his seminal contributions to this new field of astronomy. The vice-president is Alan Boss, the former chair of the WG-ESP, and the members of the Commission 53 Organizing Committee are the other former members of the WG-ESP.
Bioastronomy: Search for Extraterrestrial Life was established as Commission 51 of the IAU in 1982. The objectives of the commission included: the search for planets around other stars; the search for radio transmissions, intentional or unintentional, of extraterrestrial origin; the search for biologically relevant interstellar molecules and the study of their formation processes; detection methods for potential spectroscopic evidence of biological activity; the coordination of efforts in all these areas at the international level and the establishment of collaborative programs with other international scientific societies with related interests. In 2006, Commission 51 was renamed simply Bioastronomy at the IAU General Assembly in Prague, and approved for the next six years, the default extension for an IAU Commission.
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.
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.
There are currently five space missions en route to or planned for comet encounters. It is important for the success of each mission that its target be characterized as fully as possible prior to the encounter. This progress report analyses initial photometric results for 11 comet nuclei for the Stardust, Rosetta, Deep Impact, CONTOUR, Deep Space 1, and the proposed Comet Nucleus Sample Return missions from a database of comet CCD images. Our 17-year database contains more than 20,500 images of ∼160 comets taken during > 1,500 observing hours (Pittichová & Meech 2000). We are undertaking a program to observe these 11 comets over a wide range of heliocentric distances to obtain information about their behavior and composition that will be particularly useful to the space missions.
Recent evidence suggests that comets formed at low temperatures (≤ 25 K) and that, while the interiors have not been considerably altered since formation, the outer layers have undergone substantial modification. Comets exhibit a wide range of physical characteristics, some of which may be attributed to systematic physical differences between comets making their first close approach to the Sun from the Oort cloud (new comets) and those having made many approaches (old comets). These differences may reflect either primordial differences between two populations or the differences may be a manifestation of aging processes. There are many processes that might be responsible for causing aging in comets. These include: (i) radiation damage in the upper layers of the nucleus during the long residences in the Oort cloud, (ii) processing from heating and collisions within the Oort cloud, (iii) loss of highly volatile species from the nucleus on the first passage through the inner Solar System, (iv) buildup of a dusty mantle, which can eventually prohibit further sublimation, and (v) a change in the porosity, and hence the thermal properties of the nucleus. Although Oort’s (1950) original work on the comet cloud required that new comets fade after their first close passage, past searches for evidence of aging in comets have produced conflicting results, partly due to a lack of systematic data sets. An understanding of the evolutionary processes of comet nuclei that give rise to compositional or physical differences between ‘fresh’ Oort cloud comets and thermally processed periodic comets will improve our knowledge of the possibly primordial comet composition and therefore conditions in the early Solar System. Recent observations suggest that there are distinct differences between the two groups with respect to intrinsic brightness and rate of change of activity as a function of distance.
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