A Case Study of Interstellar Material Delivery: α Centauri

Abstract

Interstellar material has been discovered in our Solar System, yet its origins and details of its transport are unknown. Here we present $α$ Centauri as a case study of the delivery of interstellar material to our Solar System. $α$ Centauri is a mature triple star system that likely harbours planets and is moving towards us with the point of closest approach approximately 28,000 years in the future. Assuming a current ejection model for the system, we find that such material can reach our Solar System and may currently be present here. The material that does reach us is mostly a product of low ($<2$ km/s) ejection velocities, and the rate at which it enters our Solar System is expected to peak around the time of $α$ Centauri 's closest approach. If $α$ Centauri ejects material at a rate comparable to our own Solar System, we estimate the current number of $α$ Centauri particles larger than 100 m in diameter within our Oort Cloud to be $10^{6}$, and during $α$ Centauri 's closest approach, this will increase by an order of magnitude. However, the observable fraction of such objects remains low as there is only a probability of $10^{-6}$ that one of them is within 10 au of the Sun. A small number ($\sim 10$) meteors greater than 100 micrometers from $α$ Centauri may currently be entering Earth's atmosphere every year: this number is very sensitive to the assumed ejected mass distribution, but the flux is expected to increase as $α$ Centauri approaches.