Institute of Astronomy

Planet Formation in Evolved Binary Star Systems

SpeakerTalk DateTalk Series
Nader Haghighipour28 July 2014Across HR 2014 Talks


The discovery of planets in close binary systems (i.e., stellar separations ? 50 AU) has lent strong support to the fact that planet formation around a star of a binary is robust, and these systems (known as S-type binaries) can host a variety of planets. At present, there are six close S-type systems that host planetary bodies: GJ86, ?-Cephei, HD41004, HD196885, HD176051, and ?-Centauri. While in the last four, the components of the binary are main sequence stars, the primary of ?-Cephei (which is also the planet-hosting star) is a K1-IV sub-giant, and in GJ86 system, the secondary is a white dwarf (suggesting that the planet orbits the originally less massive star). The discovery of planets in such evolved binaries has raised questions regarding their formation and orbital evolution. It is possible that planets did not form in their current orbits and around their current stars. For instance, in the case of GJ86, the initial binary separation was smaller, making this systems a challenging environment for planets to form. We have developed a comprehensive model for the formation of planets around a star of a binary that takes into account stellar evolution, in particular the changes in the binary separation and stellar mass loss. Our model indicates that in binaries similar to GJ86, planet might have formed while the binary separation was increasing and reached its current orbit through interactions with the binary and/or possibly other planets in the system. We will present our model and discuss its applications and results.