{"references": ["\u201cMassive perturber-driven interactions between stars and a massive black hole, Perets, Hopman, & Alexander, The Astrophysical Journal, Volume 656, Issue 2, pp. 709-720 (2007).", "\u201cMassive perturbers and the efficient coalescence of binary massive black holes, Perets & Alexander, The Astrophysical Journal, Volume 677, Issue 1, pp. 146-159 (2008).", "\u201cDynamical and evolutionary constraints on the nature and origin of hypervelocity stars\u201d, Perets, The Astrophysical Journal, Volume 690, Issue 1, pp. 795-801 (2009).", "\u201cRunaway and hypervelocity stars in the Galactic halo: Binary rejuvenation and triple disruption\u201d, Perets, The Astrophysical Journal, in press (2009)", "\u201cThe Galactic potential and the asymmetric distribution of hypervelocity stars\u201d, Perets et al., The Astrophysical Journal, Volume 697, Issue 2, pp. 2096-2101 (2009).", "\u201cDynamical evolution of the young stars in the Galactic center: N-body simulations of the S-stars\u201d, Perets, Gualandris, Kupi, Merritt, & Alexander, The Astrophysical Journal, in press (2009).", "\u201cMolecular hydrogen formation on amorphous silicates under interstellar conditions\u201d, Perets et al., The Astrophysical Journal, Volume 661, Issue 2, pp. L163-L166 (2007)", "\u201cRealization of quantum walks with negligible decoherence in waveguide lattices\u201d, Perets et al., Physical Review Letters, vol. 100, Issue 17, id. 170506 (2008)", "\u201cOn the triple origin of blue stragglers\u201d Perets & Fabrycky, The Astrophysical Journal, Volume 697, Issue 2, pp. 1048-1056 (2009)", "\u201cKozai cycles, tidal friction and the dynamical evolution of binary minor planets\u201d, Perets & Naoz, ApJL, in press (2009)."]}

The configuration of a central massive object interacting gravitationally with much lighter objects around it (so called near Keplerian system) appears on many astrophysical scales. At the largest scales massive black holes (MBHs; thought to exist in most if not all galactic nuclei,) and the stellar systems around them, exemplify such systems. Close interactions of stars with MBHs lead in many cases to catastrophic outcomes; a star or a binary star could be disrupted following a close encounter with the MBH; a compact object, such as a stellar black hole, neutron stars or a white dwarf may inspiral to the MBH, through gravitational wave (GW) emission. In this Thesis the dynamics of stars and their close interactions near MBHs are studied. We explore several directions including the effects of massive perturbers such as giant molecular clouds on the dynamics of stars near MBHs; the close interaction of stars and binary stars with MBHs and their rates; and the origin and dynamical evolution of hypervelocity stars ejected by MBHs. We show that massive perturbers can accelerate relaxation processes in Galactic nuclei by orders of magnitude. Scattering of stars by such perturbers can explain the origin of the young stars observed very close to the MBH in the Galactic center, as well as the origin of hypervelocity stars observed in the Galactic halo. Massive perturbers could also have a major role in the coalescence of binary MBHs and induce their merger in short times, leading to their inspiral through GW emission, likely to be observable with future space programs. We also obtained strong constraints on the origin of hypervelocity stars, and found a novel method to use them as probes of the Galactic potential at large scales.