Title: Helium-like atom as a classical three-body problem. Author: T.J. Stuchi(1), A.C.B. Antunes(1) and M.A. Andreu(2). Adress: (1) Instituto de Fisica, Universidade Federal do Rio de Janeiro, Caixa Postal 68.528, 21945-970 Rio de Janeiro, RJ, Brazil. e-mail: tstuchi@if.ufrj.br (2) Dept. Matematica Aplicada i Analisi, Univ. Barcelona. Gran Via 585, 08007--Barcelona (Spain). e-mail: mangel@maia.ub.es Abstract: We study the classical problem of the muonic helium atom, a helium atom with one of its electrons replaced by a muon. Firstly, we establish the connection of the model with the one-dimensional frozen planetary approximation of the helium atom. After that, we find that there is only an equilibrium configuration if the particles are allowed a non-zero angular momentum with the alpha/muon distance restricted. We then present the restricted muonic helium problem, an approximation for the movement of the electron in the potential of the alpha/muon pair moving in a circular orbit. In this model we find that there is only an equilibrium point of the type center-saddle-center. The planar and vertical Lyapunov families of periodic orbits and their stability parameters have been studied showing that the planar family bifurcate into Halo orbits like its gravitational counterpart. The most interesting feature is the stability of these Halo orbits for a range of energy values. The vicinity of the alpha particle is also studied using a Levi--Civita regularization of the electron-alpha particle collision. The movement gets more and more chaotic as the energy increases. However, we find that retrograde zones of bounded stability are possible for energies higher than that of the equilibrium point, when the zero velocity curves open.