Denys Wilkinson Building, Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH
Professor Hagai Perets, Technion
The importance of being wide: The key role of wide binaries, from GW sources to Pluto
Dense stellar clusters are known to be hotbeds of collisional stellar dynamics, driving a diverse array of phenomena, from gravitational-wave sources and X-ray binaries to blue stragglers. While the Galactic field is typically considered too sparse for such interactions, this view overlooks the significant role of ultra-wide binaries and triples (separations > 1000 AU). These systems possess large cross-sections for encounters, leading to surprisingly high interaction rates even in low-density environments. Cumulative effects from repeated flybys can trigger strong interactions between system components, effectively enabling collisional dynamics and associated phenomena within the field.
Shifting focus to smaller scales, wide binary Kuiper Belt objects can also undergo mergers and collisions. However, instead of direct collisions, these events are driven by secular evolution within hierarchical triple systems. This mechanism offers a compelling explanation for the formation of objects like Arrokoth and the Pluto-Charon system.