RSAA Colloquium: John Forbes (U. Canterbury)

The Galaxy's population of interstellar objects in the Rubin era.

Comets and asteroids from other stars are evidently ejected from their home planetary systems in large numbers, around 10^16 per star. Once ejected, these "interstellar objects" (ISOs) orbit the Galaxy. Three such objects have been discovered as they traversed our Solar System on hyperbolic orbits, with the Vera C. Rubin Observatory expected to find many more in the course of its survey. When a population of ISOs is ejected, it is stretched into a thin tidal stream. The ISO streams themselves are subject to epicyclic caustics, and their density structures are highly sensitive to their internal velocity dispersions. This means that a future observed population of interstellar objects may contain "sibling" ISOs from the same parent star, and that these may preferentially originate in particular parts of the population's parameter space. 

I will also show under what circumstances the Sun's own ISOs may return to the Solar System, demonstrating that this is not a foreground ISO imposter population about which we need to be concerned, and future prospects for tracing an ISO to its host star.