Saas-Fee Advanced Course 35 D. Jewitt A. Morbidelli H. Rauer Trans-Neptunian Objects and Comets Saas-Fee Advanced Course 35 Swiss Society for Astrophysics and Astronomy Edited by K. Altwegg, W. Benz and N. Thomas With 132 Figures, 18 in Color David Jewitt Heike Rauer University of Hawaii DLR/Institut für Planetenforschung Institute for Astronomy Rutherfordstr. 2 2680 Woodlawn Drive 12489 Berlin, Germany Honolulu, HI 96822, USA and [email protected] TU Berlin/Zentrum für Astronomie und Astrophysik Alessandro Morbidelli Hardenbergstr. 36 10623 Berlin, Germany Observatoire de la Côte [email protected] dŠAzur/CNRS B.P. 4229 06304 Nice Cedex 4, France [email protected] Volume Editors: Kathrin Altwegg Willy Benz Nicolas Thomas Universität Bern Physikalisches Institut Sidlerstrasse 5 3012 Bern, Switzerland This series is edited on behalf of the Swiss Society for Astrophysics and Astronomy: Société Suisse d’Astrophysique et d’Astronomie Observatoire de Genève, ch. des Maillettes 51, 1290 Sauverny, Switzerland Cover picture: See chapter by D. Jewitt, Fig. 12. Library of Congress Control Number: 2007934029 ISBN 978-3-540-71957-1 Springer Berlin Heidelberg New York This work is subject to copyright. All rights are reserved, whether the whole or part of the material is concerned, specifically the rights of translation, reprinting, reuse of illustrations, recitation, broadcasting, reproduction on microfilm or in any other way, and storage in data banks. Duplication of this publication or parts thereof is permitted only under the provisions of the German Copyright Law of September 9, 1965, in its current version, and permission for use must always be obtained from Springer. Violations are liable for prosecution under the German Copyright Law. Springer is a part of Springer Science+Business Media springer.com c Springer-Verlag Berlin Heidelberg 2008 The use of general descriptive names, registered names, trademarks, etc. in this publication does not imply, even in the absence of a specific statement, that such names are exempt from the relevant protective laws and regulations and therefore free for general use. Typesetting: by the authors and Integra using a Springer LATEX macro package Cover design: WMXDesign GmbH, Heidelberg Printed on acid-free paper SPIN: 11808169 55/Integra 5 4 3210 Preface The 35th Saas Fee Winter School was held on 13–18 March 2005 in the skiing village of M¨urren in the Berner Oberland. In view of the excitement generated over the past 15 years by the discovery of the Kuiper Belt and Trans-Neptunian Objects and also by the ongoing Rosetta mission to comet Churyumov-Gerasimenko, it was decided to combine discussion of these prim- itive objects into one winter school under the title, “Trans-Neptunian Objects and Comets.” The aim was to provide an overview of these objects, to discuss their relationships, and to identify directions for future research. The school attracted over 60 students from all over the world. We were fortunate that not merely were the students able to hear a set of outstanding lectures but were also able to enjoy marvellous weather in one of the most beautiful parts of Switzerland. The organizers thank the lecturers, Dave Jewitt, Alessandro Morbidelli, and Heike Rauer, for the tremendous effort they made in preparing the lectures and the text for this volume. Stephan Graf, Annette J¨ackel, and Jonathan Horner provided reviews, checked the text and references, and as- sisted in the production. We also thank Frau Staehli and the staff of the Hotel Eiger in M¨urren for the warm welcome and their generosity. We also thank Ms. Kathrin Weyeneth and Ms. Edith Hertig from the Physikalisches Institut for their secretarial support for the school. Financial assistance provided by the Swiss Society for Astrophysics and Astronomy and the European Space Agency is gratefully acknowledged. Kathrin Altwegg Willy Benz Nicolas Thomas Contents Kuiper Belt and Comets: An Observational Perspective D. Jewitt ....................................................... 1 1 Preamble.................................................... 1 1.1 The Conduct of Research into the Subject . 2 2 TheModernSolarSystem..................................... 5 2.1 ProtoplanetaryDisk ..................................... 5 2.2 TheThreeDomains...................................... 9 3 CometaryNuclei............................................. 26 3.1 Mantles ................................................ 38 4 KuiperBelt.................................................. 47 4.1 KuiperBeltPhysicalProperties:ColorsandAlbedos......... 47 4.2 KuiperBeltPhysicalProperties:Spectra.................... 53 4.3 KuiperBeltPhysicalProperties:Shapes,Spins.............. 56 4.4 KuiperBeltPhysicalProperties:MultipleObjects ........... 57 4.5 KuiperBeltPhysicalProperties:Densities.................. 59 4.6 Centaurs ............................................... 62 4.7 Irregular Satellites . 63 4.8 Trojans................................................. 68 References...................................................... 72 Comets and Their Reservoirs: Current Dynamics and Primordial Evolution A. Morbidelli .................................................... 79 1 TheTrans-NeptunianPopulation............................... 80 1.1 BriefTutorialonOrbitalDynamics........................ 80 1.2 The Structure of the Trans-NeptunianPopulation............ 84 1.3 DynamicsintheKuiperBelt.............................. 93 1.4 NoteontheScatteredDisk ...............................100 2 TheDynamicsofComets......................................101 2.1 OriginandEvolutionofJupiterFamilyComets..............104 2.2 OriginandEvolutionofLong-PeriodComets................108 VIII Contents 2.3 NoteonHalley-TypeComets..............................113 2.4 TheFateofFadedComets................................115 3 TheFormationoftheOortCloud ..............................117 3.1 ProblemswiththeClassicalScenario.......................122 3.2 Oort Cloud Formation in a Dense Galactic Environment . 124 4 ThePrimordialSculptingoftheKuiperBelt.....................127 4.1 TheOriginoftheResonantPopulations....................128 4.2 TheOriginoftheHotPopulation..........................130 4.3 The Origin of the Outer Edge of the Kuiper Belt . 132 4.4 TheMassDeficitoftheColdPopulation....................134 4.5 PushingouttheKuiperBelt..............................138 5 Origin of the Late Heavy Bombardment oftheTerrestrialPlanets......................................139 6 Building a Coherent View of Solar System History: Perspectives forFutureWork..............................................151 References......................................................154 Comets H. Rauer .......................................................165 1 Introduction.................................................165 2 SublimationProcesses ........................................168 2.1 GeneralOverview........................................168 2.2 GasSublimationandNucleusDifferentiation................170 2.3 ObservationsofGasActivityEvolution.....................175 3 ComaandTailDynamics .....................................182 3.1 DynamicsoftheNeutralComa ...........................182 3.2 Dynamics in the Outer Coma and Neutral Gas Tails . 200 3.3 DynamicsofDustTails ..................................201 3.4 DynamicsofIonTails ...................................204 4 EmissionExcitationintheGasComa ..........................208 4.1 ResonanceFluorescence ..................................212 4.2 PromptEmission........................................213 4.3 OpticalDepthEffects....................................214 4.4 Excitation of Rotational and Vibrational Transitions . 214 4.5 OHMaserEmission......................................216 4.6 X-rayEmission..........................................216 5 ChemicalProcessesintheComa ...............................216 5.1 ChemistryofSomeFrequentlyObservedSpecies.............219 6 GasProductionRates ........................................224 6.1 SimpleComaModels.....................................224 6.2 Abundance Ratios and Compositional DifferencesamongComets................................226 6.3 CompositionalDifferencesAmongComets ..................230 6.4 IsotopicRatios..........................................231 Contents IX 7 DustParticles ...............................................233 7.1 Composition............................................234 7.2 SizeDistribution.........................................236 7.3 TheDustProductionRate................................238 8 Outlook.....................................................240 References......................................................242 Acknowledgments .............................................255 Index ..........................................................257 List of Previous Saas-Fee Advanced Courses !! 2005 Trans-Neptunian Objects and Comets D. Jewitt, A. Morbidelli, H. Rauer !! 2004 The Sun, Solar Analogs and the Climate J.D. Haigh, M. Lockwood, M.S. Giampapa !! 2003 Gravitation Lensing: Strong, Weak and Micro P. Schneider, C. Kochanek, J. Wambsganss !! 2002 The Cold Universe A.W. Blain, F. Combes, B.T. Draine !! 2001 Extrasolar Planets T. Guillot, P. Cassen, A. Quirrenbach !! 2000 High-Energy Spectroscopic Astrophysics S.M. Kahn, P. von Ballmoos, R.A. Sunyaev !! 1999 Physics of Star Formation in Galaxies F. Palla, H. Zinnecker !! 1998 Star Clusters B.W. Carney, W.E. Harris !! 1997 Computational Methods for Astrophysical Fluid Flow R.J. LeVeque, D. Mihalas, E.A. Dorfi, E. M¨uller !! 1996