Math 2.0

Mechanics of particles and systems Particle systems and celestial mechanics Problem

Circular restricted three-body problem

Builds on Three-body problemTwo-body problemRotating reference frameHamiltonian systemFirst integralChaos theory

Problem

Let μ∈(0,12]\mu \in (0, \frac{1}{2}]. Two bodies, the primaries, have masses 1−μ1 - \mu and μ\mu. They move on circles around their common centre of mass, at distance 11 from each other and with angular velocity 11. This is a circular solution of the two-body problem, in units where the gravitational constant times the total mass is 11. A third body of negligible mass moves in their gravitational field and does not affect them. Use the rotating frame in which the primaries stay at (−μ,0,0)(-\mu, 0, 0) and (1−μ,0,0)(1 - \mu, 0, 0). In this frame the position (x,y,z)(x, y, z) of the third body satisfies x′′−2y′=∂Ω∂x,y′′+2x′=∂Ω∂y,z′′=∂Ω∂z,x'' - 2 y' = \frac{\partial \Omega}{\partial x}, \qquad y'' + 2 x' = \frac{\partial \Omega}{\partial y}, \qquad z'' = \frac{\partial \Omega}{\partial z}, where Ω(x,y,z)=x2+y22+1−μr1+μr2,\Omega(x, y, z) = \frac{x^2 + y^2}{2} + \frac{1 - \mu}{r_1} + \frac{\mu}{r_2}, and r1=(x+μ)2+y2+z2r_1 = \sqrt{(x + \mu)^2 + y^2 + z^2} and r2=(x−1+μ)2+y2+z2r_2 = \sqrt{(x - 1 + \mu)^2 + y^2 + z^2} are the distances to the primaries. Given the initial position and velocity of the third body, describe its motion for all time.

Remarks

The problem is a limit case of the three-body problem in which one mass tends to 00. It is a Hamiltonian system with three degrees of freedom, or two in the planar case z=0z = 0. Its Hamiltonian does not depend on time, because the frame rotates with the primaries. The quantity 2Ω−(x′2+y′2+z′2)2 \Omega - (x'^2 + y'^2 + z'^2) is a first integral, the Jacobi integral. Check: multiplying the three equations by x′,y′,z′x', y', z' and adding gives 12ddt(x′2+y′2+z′2)=ddtΩ\frac{1}{2} \frac{d}{dt}(x'^2 + y'^2 + z'^2) = \frac{d}{dt} \Omega, since the Coriolis terms cancel. Poincaré showed that the problem has no further analytic first integral, and its motion is in general chaotic. There are five equilibrium points in the rotating frame, the Lagrange points. The model describes, to a first approximation, a spacecraft in the Earth–Moon system or an asteroid moving under the Sun and Jupiter.

Reading path

To understand this page from the ground up, read these 73 pages in order. The foundations come first.

  1. Chaos theory concept
  2. Conic section concept
  3. Cross product concept
  4. Derivative concept
  5. Differential equation concept
  6. Ellipse concept
  7. Euclidean space object
  8. Euclidean vector concept
  9. First integral concept
  10. Focus of a conic concept
  11. Function concept
  12. Hamiltonian system concept
  13. Identity matrix object
  14. Interval concept
  15. Matrix definition
  16. Ordinary differential equation concept
  17. Vector space definition
  18. Velocity concept
  19. Kepler problem example
  20. Fréchet derivative definition
  21. Cross product definition
  22. Ordinary differential equation definition
  23. Function of several variables concept
  24. Vector-valued function concept
  25. Lipschitz condition definition
  26. Classical mechanics concept
  27. n-body problem problem
  28. Square matrix definition
  29. Transpose definition
  30. Linear map definition
  31. Momentum concept
  32. Double integral concept
  33. Partial derivative concept
  34. Limit of a function of several variables concept
  35. Inertial frame of reference concept
  36. Solution of an ordinary differential equation definition
  37. Orthogonal matrix definition
  38. Three-body problem problem
  39. Multilinear map definition
  40. Triple integral concept
  41. Newton's laws of motion statement
  42. Continuity in R^n definition
  43. Differentiable function of several variables definition
  44. Initial value problem definition
  45. Partial derivative definition
  46. Orthogonal group object
  47. Alternating multilinear map definition
  48. Centre of mass concept
  49. Differentiable on an open set definition
  50. Gradient definition
  51. Higher partial derivatives definition
  52. Picard–Lindelöf hypotheses definition
  53. Determinant definition
  54. Reduced mass concept
  55. Iterated derivative definition
  56. Picard operator definition
  57. Special orthogonal group object
  58. Angular velocity concept
  59. C^k function characterised by continuous derivatives statement
  60. Integral equation form of an initial value problem statement
  61. An iterate of the Picard operator is a contraction statement
  62. Rotating reference frame concept
  63. Vector field definition
  64. Picard–Lindelöf theorem statement
  65. Conservative vector field definition
  66. Classical mechanics definition
  67. Momentum definition
  68. Potential energy definition
  69. Angular momentum definition
  70. Central force definition
  71. Newton's law of universal gravitation statement
  72. Two-body problem problem
  73. Circular restricted three-body problem problem

Where this leads

7 pages build on this one.

Further reading

  1. Web https://en.wikipedia.org/wiki/Three-body_problem, Restricted three-body problem
About this page
TagY2R2QRPD1B
URIm2://Y2R2QRPD1B
Kindproblem
WritingW0 stub
MSC70F07, 70F15, 37N05
StatusThis copy of the site has no build data. Run m2 status Y2R2QRPD1B.
AboutThree-body problem
UsesThree-body problem, Two-body problem, Rotating reference frame, Hamiltonian system, First integral, Chaos theory
Changed3 November 2026

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