Title:

Dynamics of Binary Stars and their Planets



Eric Pfahl
KITP, UC Santa Barbara



Abstract:

Among the stars known to host a planet, roughly 25% have a binary
stellar companion.  Most of these binaries have orbital separations of
 >100 AU, but a handful are hazardously close, with separations of 20
AU or less.  The presence of a close stellar companion can prohibit
giant planet formation.  I will discuss the hypothesis that some
fraction of planet-hosting stars that are now in binaries were
initially single.  This idea is motivated by recent evidence that most
stars, including the Sun, were born in clusters with hundreds to
thousands of members.  In a cluster environment, an initially single
star can acquire a close companion during a three-star dynamical
interaction.  Similar processes can dissolve wide binaries; as an
example, I will assess the possibility that the Sun had a distant
companion at early times, and consider what dynamical imprints that
star may have left on the Solar System.