The Solar System as an Exosystem: Planet Confusion

Abstract

Future, large-scale, exoplanet direct-imaging missions will be capable of discovering and characterizing Earth-like exoplanets and star systems like our solar system. However, a telescope capable of detecting Earth-like exoplanets would also be sensitive to a myriad of non-Earth-like exoplanets in the exoplanet population with the same instantaneous planet–star separation (s) and planet–star difference in magnitude (Δmag). Here, we consider the solar system as a previously unexplored exosystem, viewed by an external direct-imaging observer for the first time. We find that an external observer could see as many as six (s, Δmag)-coincidence locations between the Earth and other solar system planets. We determine locations of (s, Δmag)-coincidence of solar system planets using realistic planet phase functions and planet properties. By varying system inclinations, we found 36%–69% of inner planet orbits and 1%–4% of outer planet orbits share at least one (s, Δmag)-coincidence with the Earth.