Background Information
Black Holes

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An interesting question is what happens to orbits of stars if there is a massive central object in the center of the galaxy, say a massive black hole. In this case, as stars move close to the center of the galaxy, they will feel not only the general gravitational field of the galaxy but also the pull of the black hole. This can act to scatter stars off of their original orbits. The most obvious potential victims of this process are stars on box orbits, since they are the ones that move through the center.
If box orbits are destroyed by black holes, astronomers have proposed that galaxies with massive central black holes cannot be very triaxial. Since it is the box orbits which support triaxiality, no box orbits means no triaxiality. This would be of great importance to studies of galactic evolution, as it means that changes to the nucleus of a galaxy could have a profound impact on the galaxy as a whole. Studies of how black holes drive evolution in their host galaxy are ongoing.
Box Orbit with black hole scattering
Figure 9 - left: a box orbit which has been scattered by a central black hole. Note the lack of regularity in the orbit. right: the surface of section for this orbit. Again, note the chaotic nature of the surface of section, indicative of scattering.
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