Comets: Nature, Dynamics, Origin, and their Cosmogonical Relevance

Table of contents......Page 6
1 Preface......Page 10
1 Early ideas about comets......Page 12
1.1 Early records of comet apparitions......Page 13
1.2 Heavenly bodies or atmospheric phenomena?......Page 16
1.3 The confirmation of their celestial nature......Page 19
1.4 The determination of their trajectories......Page 22
1.5 Interstellar visitors or members of the solar system?......Page 24
2 Statistics of comet orbits and magnitudes......Page 29
2.1 The orbital elements and Kepler’s laws......Page 30
2.2 Periodic and nonperiodic orbits......Page 32
2.3 Naming procedure......Page 34
2.4 Total and nuclear magnitudes......Page 35
2.5 Selection effects......Page 41
2.6 The distribution of perihelion distances......Page 43
2.7 The discovery rate and the flux of new and LP comets......Page 46
3.1 Comet sizes and masses......Page 49
3.2 ‘Sand bank’ versus ‘dirty snowball’ model......Page 51
3.3 The solid nucleus......Page 52
3.4 Sublimation of volatiles......Page 54
3.5 Spectroscopic observations......Page 59
3.6 Inventory of parent molecules......Page 63
3.7 Distribution of parent molecules and radicals in the coma......Page 66
3.8 The hydrogen corona......Page 69
3.9 The nature of dust particles......Page 73
3.10 The dust to gas mass ratio......Page 77
3.11 Formation of the tails......Page 80
4.1 The original orbit......Page 86
4.2 Change in the orbital energy......Page 87
4.3 Nongravitational forces......Page 90
4.4 Resonant and non-resonant motion......Page 94
4.5 Random-walk in the energy space......Page 96
4.6 The diffusion equation......Page 99
4.7 Dynamical time scale for capture into a periodic orbit......Page 100
4.8 Dynamical losses......Page 101
4.9 The capture problem......Page 104
4.10 From “new” comets to “old” comets. The problem of physical decay......Page 105
4.11 Changes in the inclination-distribution of LP comets with the dynamical age......Page 108
5 The Oort cloud......Page 112
5.1 The distribution of original energies......Page 113
5.2 Stellar perturbations......Page 115
5.3 Galactic tidal forces......Page 119
5.4 Penetrating encounters with giant molecular clouds......Page 128
5.5 Randomization of orbital inclinations......Page 130
5.6 Distribution of eccentricities of a thermalized population......Page 135
5.7 The outer boundary of the Oort cloud......Page 140
6.1 The drift of the perihelion distance under external perturbers......Page 142
6.2 The Jupiter-Saturn barrier......Page 145
6.3 The ”inner” and ”outer” Oort cloud. The possible existence of an inner core......Page 147
6.4 The fluxes of Oort cloud comets in the inner and outer planetary region......Page 150
6.5 Comet showers......Page 153
6.6 Do comet showers reflect in the impact cratering record?......Page 159
6.7 The current passage rate of Oort cloud comets: does it represent a quiescent stage or an excited one?......Page 162
7.1 Statistics of comet discoveries and orbital properties......Page 164
7.2 Determination of comet sizes: methods......Page 168
7.3 The size distribution......Page 176
7.4 Nongravitational forces and masses......Page 181
7.5 Lightcurves, shapes and rotation periods......Page 184
7.6 Color, albedo and phase function......Page 190
7.7 Dynamics of close encounters......Page 192
7.8 The population size......Page 196
7.9 The source region......Page 199
8 The trans-neptunian belt......Page 202
8.1 The puzzle of the Jupiter family comet population......Page 204
8.2 The discovery......Page 205
8.3 The naming debate......Page 207
8.4 Resonance dynamics......Page 208
8.5 Dynamical structure and transfer mechanisms......Page 213
8.6 Transient objects......Page 218
8.7 Population size and size distribution......Page 220
8.8 Binary TNOs......Page 225
8.9 The outer edge of the belt......Page 227
8.10 Dynamical and physical erosion of the belt......Page 229
8.11 The trans-neptunian belt as a replenishment source of the Oort cloud......Page 234
8.12 Physical properties of trans-neptunian objects and Centaurs......Page 237
9.1 The sublimation of the volatile material......Page 245
9.2 Formation of a dust mantle......Page 248
9.3 Can defunct or dormant comets be disguised as asteroids?......Page 254
9.4 Splitting events......Page 257
9.5 Possible scenarios for the physical evolution and decay of a comet......Page 264
9.6 Small comets......Page 267
9.7 Collision with the Sun......Page 270
9.8 Collisions with the planets......Page 273
9.9 Collisions with asteroids and interplanetary boulders......Page 275
10.1 Early phases of star formation......Page 280
10.2 Circumstellar disks......Page 283
10.3 The protoplanetary disk of the early Sun......Page 285
10.4 Grain assemblage and formation of planetesimals......Page 288
10.5 From planetesimals to planets......Page 293
10.6 Outward transport of planetesimals by resonant coupling with the outward-drifting proto-Neptune: The buildup of the trans-neptunian belt......Page 299
10.7 The scattering of residual planetesimals and the buildup of the Oort cloud......Page 304
10.8 The early galactic environment of the solar system......Page 306
10.9 The physical structure of icy planetesimals......Page 310
10.10 Chemistry of icy planetesimals......Page 313
10.11 The collisional history of comets......Page 317
10.12 How well preserved is the comet material?......Page 318
11.1 The volatile content of the Earth: endogenous or exogenous?......Page 321
11.2 The post-accretion heavy bombardment......Page 323
11.3 Comet contribution to the atmospheres of the terrestrial planets......Page 326
11.4 Comet contribution to the impact rate for the last 3800 Myr......Page 329
11.5 The deuterium problem......Page 334
11.6 May comets harbor lifeforms?......Page 337
11.7 Space missions to comets......Page 340
Appendix 1. Table A1: Astronomical and physical constants......Page 346
Appendix 2. Table A2: Absolute nuclear magnitudes and radii of JF comets......Page 348
References......Page 351
C......Page 378
D......Page 380
H......Page 381
L......Page 382
O......Page 383
S......Page 384
W......Page 385
Z......Page 386