Division Iii: Planetary Systems Science
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Transactions IAU, Volume XXVIIB Proc. XXVII IAU General Assembly, August 2009 c International Astronomical Union 2010 Ian F. Corbett, ed. doi:10.1017/S174392131000493X DIVISION III PLANETARY SYSTEMS SCIENCE PRESIDENT EDWARD L. G. BOWELL VICE-PRESIDENT Karen J. Meech PAST PRESIDENT Iwan P. Williams BOARD Alan Boss, Guy J. Consolmagno, R´egis Courtin, Julio A. Fern´andez, Bo A˚ S. Gustafson, Walter F. Huebner, Anny-Chantal Mikhail Ya. Marov, Levasseur-Regourd, Michel Mayor, Rita M. Schulz, Pavel Spurn´y Giovanni B. Valsecchi, Jun-ichi Watanabe, Adolf N. Witt. PARTICIPATING COMMISSIONS Commission 15 Physical Study of Comets and Minor Planets Commission 16 Physical Study of Planets and Satellites Commission 20 Positions and Motions of Minor Planets, Comets and Satellites Commission 21 Light of the Night Sky Commission 22 Meteors, Meteorites, and Interplanetary Dust Commission 51 Bioastronomy Commission 53 Extrasolar Planets DIVISION WORKING GROUPS Physical Study of Comets Physical Study of Minor Planets Motions of Comets Distant Objects Meteor Shower Nomenclature Professional-Amateur Cooperation in Meteors Small Bodies Nomenclature Planetary Systems Nomenclature SERVICES Minor Planet Center Minor Planet Center Advisory Committee INTER DIVISION WORKING GROUPS Division III / Division I Near-Earth Objects (WGNEOs) Division III / Division I Cartographic Coordinates and Rotational Elements of Planets and Satellites 158 Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 29 Sep 2021 at 10:03:48, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S174392131000493X PLANETARY SYSTEMS SCIENCES 159 PROCEEDINGS BUSINESS SESSIONS, Monday 10 August 2009 1. Introduction 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. 2. Division III Structure Bowell reviewed the new membership applications (by Commission): Commission 15 (Physical Study of Comets and Minor Planets) has 47 new applicants, Commission 16 (Physical Study of Planets and Satellites) 47, Commission 20 (Positions and Motions of Minor Planets, Comets and Satellites) 25, Commission 21 (Light of the Night Sky) 5, Commission 22 (Meteors, Me- teorites and Interplanetary Dust) 22, Commission 51 (Bioastronomy) 27 , and Commission 53 (Extrasolar Planets) has 72 new applicants. As it is likely that applicants have joined more than one commission, all that can be concluded is that the total number of new members of Division III ranges from somewhere between 72 and 245 new members; probably the number is around 150, which would represent a 15% increase in Division III membership. At present, the officers of the Division include the Division Board, consisting in total of 17 members including the Pres- ident, Vice President, Past President, Secretary, Organizing Committee. The IAU guidelines recommend that the board membership be between 8 and 12 members; however, this is just a guideline and the previous larger board was accepted by the Executive Committee. We are the third largest of the twelve divisions and we have an unusually large number of commissions; and so, to have presidents on the board we’re bound to have a complex structure. There are seven Commissions, five Commission Working Groups (which are expected to last longer than a triennium), several Commission Task Force/Groups (which are expected to go away after a fixed time), one Division Service, one Division Advisory Committee, two Division Working Groups, and two Interdivisional Working Groups. These are the commissions and working groups: Commission 15: Physical Study of Comets and Minor Planets WG Physical Study of Comets WG Physical Study of Minor Planets Commission 16: Physical Study of Planets and Satellites Commission 20: Positions and Motions of Minor Planets, Comets, and Satellites WG Motions of Comets WG Distant Objects Commission 21: Light of the Night Sky Commission 22: Meteors, Meteorites, and Interplanetary Dust TF Meteor Shower Nomenclature WG Professional-Amateur Cooperation in Meteors Commission 51: Bioastronomy Commission 53: Extrasolar Planets Service: Minor Planet Center Advisory Committee: Minor Planet Center WG: Committee on Small Bodies Nomenclature WG: Planetary System Nomenclature IWG: Cartographic Coordinates and Rotational Elements of Planets and Satellites (jointly with Division I: Fundamental Astronomy) IWG: Natural Planetary Satellites (jointly with Division I) The status of Commission 21, Light of the Night Sky, was discussed. (Note this commission is not to be confused with the commission on light pollution.) In 2006 it had been recommended that the future status of this commission be reviewed. As it happens, only about ten percent of the membership of C21 works in the field of planetary systems. Most C21 members are working on various aspects of diffuse or integrated galactic and extragalactic backgrounds. Thus C21, as currently constituted, does not really fit within DIII. Therefore it is proposed that the present Commission 21 “Light of the Night Sky”, as it currently exists within IAU Division III “Plane- tary Systems Sciences”, be dissolved; a new Commission 21 with the designation “Galactic and Downloaded from https://www.cambridge.org/core. IP address: 170.106.35.229, on 29 Sep 2021 at 10:03:48, subject to the Cambridge Core terms of use, available at https://www.cambridge.org/core/terms. https://doi.org/10.1017/S174392131000493X 160 DIVISION III Extragalactic Background Radiation” will be formed; the new Commission 21 will be located within IAU Division IX: “Optical and Infrared Techniques”; and these changes shall go into effect with the conclusion of the 2009 IAU General Assembly in Rio de Janeiro. Those members of C21 working on planetary systems science will be welcomed into C22 (Meteors, Meteorites and Interplanetary Dust), where their interests will be well served. The proposed action has been approved by the DIII and DIX Boards, and by the IAU Executive Committee. Merging Commissions 15 and 20 was discussed. The merger was first suggested because of the apparent overlap in the science interests of C15 (Physical Study of Comets and Minor Planets) and C20 (Positions and Motions of Minor Planets, Comets and Satellites). However, further dis- cussion between the Organizing Committees of C15 and C20 and with the DIII Board indicated that there is in fact little science overlap between the two Commissions. Only about 50 people, out of a total of some 600, are members of both C15 and C20. Consequently, the Executive Committee was asked not to merge C15 and C20, and they have accepted this position. 3. Executive Committee/Division III matters Bowell reported on the three Executive Committee meetings he had attended in the last tri- ennium; there include one in Prague, after the close of the General Assembly in 2006, in Oslo in May 2008 and in Rio de Janeiro, preceding the General Assembly in 2009. The following main areas of interest to Division III were discussed at these meetings: choosing IAU-sponsored Symposia and Joint Discussions, choosing a group name for trans-Neptunian dwarf planets, the naming of dwarf planets and starting mornings at the Rio General Assembly with plenary ses- sion reviews. Concerning the choosing IAU-sponsored Symposia, Joint Discussions, and Special Sessions, Bowell noted that in the IAU as a whole, the science interests of Division III are often overshadowed by those of stellar and galactic astronomers. Even though we are one of the larger divisions, we are represented by only one Division President. We make up 1200 members of a membership of ten thousand IAU membership total. Commission VIII has another 300 planetary people, plus others in other commissions, so we are about 15% of the total IAU. Therefore, in any vote among Division Presidents to choose among competing Symposia, Joint Discussions, and Special Sessions, Division III can be at a disadvantage. The Executive Committee recognizes this, and also recognizes that many planetary science astronomers will not attend the General Assembly if there is not a Symposium, Special Session, or Joint Discussion in their field. Conse- quently, Division III’s interests are in fact well represented at GAs and during inter-GA years. Sessions at the Rio GA of interest to Division III members and co-sponsored by Division III Commissions include: Symposium 263: Icy bodies of the solar system (5 days) Special Session 6: Planetary systems as potential sites for life (2 days) Invited Discourse 2: Water on planets (James F. Bell III) Plenary Review: Icy bodies of the solar system (David Jewitt) Concerning dwarf planets, Bowell recalled that at the close of the Prague GA in 2006, we had a definition for planet, and we were using the term dwarf planet for bodies massive enough to be in hydrostatic equilibrium (“near round”), but not massive enough to clear their orbital zones. We were still lacking at least three items: A group name to replace dwarf planet; quan- titative thresholds to define the boundaries between the different groups; and a group name for transneptunian dwarf planets. The sense at Prague had been that “dwarf planet” was a term most people didn’t like. Two main candidate names were discussed (nanoplanet and subplanet), but neither gained traction. Furthermore, since that time the term “dwarf planet” has entered the public consciousness and like it or not, it would be very difficult to change it now. It is now probably too late to reopen this discussion. At the time of the Prague GA, there were no refereed publications of direct relevance to the issue of defining quantitative thresholds for the boundaries between planets, dwarf planets, and small solar system objects, and so creating task groups to attack these problems would have been premature. Since then, Soter (Astron. J. 132, 2513) has discussed planetary orbit clearing by accretion and ejection of lesser bodies; and Tancredi and Favre (Icarus 195, 851) have quantified the lower diameter limits for icy and rocky dwarf planets.