The Origin and Evolution of the Solar System

viiiContents1.6.5 Isotopic anomalies in meteorites 391.7 Comets 411.7.1 Types of comet orbit 411.7.2 The physical structure of comets 431.7.3 The Kuiper belt 452 Observations and theories of star formation 462.1 Stars and stellar evolution 462.1.1 Brightness and distance 462.1.2 Luminosity, temperature and spectral class 482.1.3 The motions of stars relative to the Sun 502.1.4 The masses of stars 512.1.5 The Hertzsprung–Russell diagram and main-sequence stars 522.1.6 The spin rates of stars 542.1.7 Evolution of stars away from the main sequence 542.2 The formation of dense interstellar clouds 592.2.1 Dense interstellar clouds 592.2.2 Heating and cooling in the ISM 592.2.3 The pressure-density relationship for thermal equilibrium 622.2.4 Jeans’ stability criterion 632.2.5 Mechanisms for forming cool dense clouds 652.3 The evolution of proto-stars 722.3.1 The Hayashi model 722.4 Observations of star formation 752.4.1 Infrared observations 752.4.2 Radio-wave observations 752.5 Observation of young stars 772.5.1 Identifying young stellar clusters 772.5.2 Age–mass relationships in young clusters 782.6 Theories of star formation 792.6.1 Stars and stellar clusters 792.6.2 A general theory of star formation in a galactic cluster 802.7 Planets around other stars 952.8 Circumstellar discs 983 What should a theory explain? 1003.1 The nature of scientific theories 1003.1.1 What is a good theory? 1003.1.2 The acceptance of new theories 1013.1.3 Particular problems associated with the Solar System 1023.2 Required features of theories 1033.2.1 First-order features 1033.2.2 Second-order features 1043.2.3 Third-order features 106