Abstract: Jeff Bary

“The Importance of Being Duplicitous:  Why Binarity Matters”

 In spite of the depiction of Luke Skywalker’s home planet of Tatooine as orbiting two suns, astronomers have long assumed that such systems would be difficult if not impossible to form and remain stable.  As a result, early radial velocity searches for exoplanets selected Sun-like stars thought to be “singular” star systems as targets.  As the field of exoplanet research matured, many host stars were found to be in wide binary or higher order triple or quadruple systems.  In these cases, the orbit of the exoplanet merely carried it about only one of the stars in the system.  Recently, the Kepler mission has discovered several exoplanetary systems (Kepler 16-b, 34-b, 35-b, 47-b, and 47-c)  in which the exoplanet(s) orbit(s) both of the host stars.  Since over 50% of field stars in the Milky Way are estimated to be in binary or higher order multiple systems, the recent Kepler discoveries widens the diversity of planetary systems and provides new locales for habitable planets to form.  While the multiplicity fraction of stars in star forming regions has been determined to be much larger than that of the field stars, the field of star formation has until now focused predominantly on the formation of planets in single star systems.  From an observer’s perspective, I will review the standard model that describes the formation of a single star and its protoplanetary disk.  We will then address the more dynamically complex binary systems by delving into my current observational program, which includes the spectroscopic monitoring of a million-year old tight binary and the spectral imaging of another wider binary system in the nearby (D~140 pc) Taurus-Auriga star forming region.  In earnest, both studies seek a better understanding of the interactions between the forming stars and their circumstellar and circumbinary disks as they evolve toward planetary systems.