Book contents
- Frontmatter
- Contents
- Preface
- PART I INTRODUCTIONS
- PART II THE CONTINUUM LIMIT: N → ∞
- PART III MEAN FIELD DYNAMICS: N = 106
- PART IV MICROPHYSICS: N = 2
- PART V GRAVOTHERMODYNAMICS: N = 106
- PART VI GRAVITATIONAL SCATTERING: N = 3
- PART VII PRIMORDIAL BINARIES: N = 4
- 24 Binaries in Star Clusters
- 25 Triple Formation and Evolution
- 26 A Non-Renewable Energy Source
- PART VIII POST-COLLAPSE EVOLUTION: N = 106
- PART IX STAR CLUSTER ECOLOGY
- Appendix A A Simple N-Body Integrator
- Appendix B Hints to Solution of Problems
- References
- Index
25 - Triple Formation and Evolution
Published online by Cambridge University Press: 05 June 2012
- Frontmatter
- Contents
- Preface
- PART I INTRODUCTIONS
- PART II THE CONTINUUM LIMIT: N → ∞
- PART III MEAN FIELD DYNAMICS: N = 106
- PART IV MICROPHYSICS: N = 2
- PART V GRAVOTHERMODYNAMICS: N = 106
- PART VI GRAVITATIONAL SCATTERING: N = 3
- PART VII PRIMORDIAL BINARIES: N = 4
- 24 Binaries in Star Clusters
- 25 Triple Formation and Evolution
- 26 A Non-Renewable Energy Source
- PART VIII POST-COLLAPSE EVOLUTION: N = 106
- PART IX STAR CLUSTER ECOLOGY
- Appendix A A Simple N-Body Integrator
- Appendix B Hints to Solution of Problems
- References
- Index
Summary
Triple systems are very familiar. The motion of the Earth and Moon around the Sun is lightly perturbed by the other planets, and if such effects are neglected it is a nice example of a triple system. Furthermore, the distance between the Earth and Moon is much smaller than their distance from the Sun, and so it is an example of what is called a hierarchical triple system. The dynamics of such a system can be understood, to a satisfactory first approximation, as two Keplerian motions. In the case of the Earth–Moon–Sun system, one of these is the familiar motion of the Moon relative to the Earth, and the other is the motion of the barycentre of the Earth–Moon system around the Sun. The barycentre lies within the Earth, in fact, and we are more familiar with the picture that the Earth orbits around the Sun, but it is more accurate to say that it is the motion of the barycentre that is approximately Keplerian. This was realised by Newton (Principia, Book I, Prop. LXV), and it was he who really originated the study of hierarchical triples.
The mass ratios in the Earth–Moon–Sun system are rather extreme. Even though the Sun is so distant, its mass is so great that it exerts a much greater force on the Moon than the Earth does.
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- The Gravitational Million–Body ProblemA Multidisciplinary Approach to Star Cluster Dynamics, pp. 236 - 245Publisher: Cambridge University PressPrint publication year: 2003