At least 20% of extrasolar planets are known to reside in binaries. Some of them, such as alpha CEN and gamma cephei, are in small separation binaries with semi-major axes less than 20 AU. In…

This federal contract award provides a USD 226,666.34 grant to the Institute for Advanced Study - Louis Bamberger & Mrs. Felix Fuld Foundation for research on the formation and dynamics of exoplanets (planets outside our solar system) within and around binary star systems. The grant, awarded by the National Aeronautics and Space Administration (NASA), will fund a project focused on understanding the complex planet formation processes in binary star environments, which present unique challenges compared to single star systems. The research aims to develop models for planetesimal accretion and protoplanetary disk evolution in binary systems, with the goal of improving our overall understanding of the origins of exoplanetary systems. This award is not designated as a set-aside contract.

At least 20% of extrasolar planets are known to reside in binaries. Some of them, such as alpha CEN and gamma cephei, are in small separation binaries with semi-major axes less than 20 AU. In addition, several circumbinary planetary systems have been recently discovered by the kepler satellite. Understanding origin of such systems puts planet formation theories to a serious test, as planetary genesis in binaries involves many complications not present in the case of single STARS. Strong dynamical excitation of planetesimals by the stellar companion, short lifetimes of protoplanetary disks - all these factors adversely affect planet formation in binaries. Recently, our group has reached progress in understanding of planetesimal dynamics in binaries and demonstrated, in particular, that gravity of protoplanetary disks plays a decisive role in the dynamics of planetesimals and their collisional outcomes. Science goals and objectives the proposed research will cover three main areas. Armed with our recent dynamical results, we will develop a complete picture of planetesimal accretion in binaries, addressing the origin of both circumstellar and circumbinary planetary systems. In addition, we will explore the physics of the gaseous component of protoplanetary disks in binaries with the goal of understanding their nonaxisymmetric structure and evolution, as the latter strongly affects planetesimal dynamics. We will subsequently integrate these diverse pieces into a coherent picture of planet formation in binaries. Methodology our study of planetesimal growth in binaries will include the following projects. We will explore the role of non-secular effects on planetesimal dynamics. These will include the possibility of evection resonance in systems with massive protoplanetary disks, effects of higher-m harmonics of the disk potential, perturbations due to the density waves excited by the companion in the disk. We will also study inclination evolution of planetesimals in disks which are misaligned with the binary orbit. We will also explore protoplanetary disk physics in binaries. (1) we will build analytical understanding of eccentricity evolution of both circumstellar and circumbinary gaseous disks in binaries. (2) we will explore the effects of disk self-gravity on its eccentricity and precession. (3) we will calculate torques excited by the companion at the disk edge and apply our results to understand the truncation radii of the circumstellar and circumbinary disks. (4) we will investigate the back-reaction of the disk-binary coupling on the binary orbit, focusing on evolution of its eccentricity and semi-major axis. These tasks will include analytical investigation as well as the numerical verification using direct hydrodynamical simulations, for both circumstellar and circumbinary disks. Finally, using our understanding of planetesimal dynamics and disk properties we will develop detailed statistical, multi-zone models of planetesimal coagulation in binary stellar systems. Relevance of the proposed research proposed research is directly relevant for the exoplanets research program. Among our goals are characterization of planets and planetary systems outside of our solar system, including the determination of their compositions and dynamics. Our results will help to explain observations of exoplanetary systems, and improve understanding of the origins of exoplanetary systems. We hope that by carrying out this research we will be able to finally settle the fragmentation barrier issue and dramatically improve our understanding of planet formation in the extreme conditions of the binary stellar systems. This will also allow US to set important constraints on theories of planetesimal origin.