# New insights from triples and implications at different scales

### Smadar Naoz (UCLA) - November 3, 2014 at 12:10 pm

Many gravitational triple systems are in a hierarchical configuration
- two objects orbit each other in a relatively tight inner binary
while the third object is on a much wider orbit. The secular
approximation for the evolution of hierarchical triple configurations
has proven to be very useful in many astrophysical contexts, from
planetary to triple-star systems. In this approximation the orbits may
change shape and orientation, on time-scales longer than the orbital
time-scales, but the semi major axes are constant. In early studies of
hierarchical secular three-body systems (Kozai 1962; Lidov 1962), the
wider orbit was set to be circular and one of the tight binary members
is assumed to be a test (massless) particle. In this situation, the
component of the tight orbit's angular momentum along the total
angular momentum is conserved, and the lowest order of the
approximation (i.e., the quadrupole approximation) is valid. I will
discussed recent developments that showed that considering systems
beyond the test particle approximation, or circular orbits, requires
the next level of approximation for a correct representation of the
physics, called the octupole-level, which leads to qualitative
different behavior of the system. In this case, the angular momenta
component of the tight and wide orbits along the total angular
momentum is not conserved. Most interestingly, at the this level of
approximation, for an eccentric wide orbit, the tight orbit can reach
extremely high eccentricities and undergo chaotic flips in its
orientation. This behavior has important implications to the evolution
of triple systems, and I will explore few examples.
The seminar will be held in 131A Campbell Hall.

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