A Resolution to the Trojan Color Conundrum?: A Photometric Survey of Neptune’s Trojan Asteroids

Sometimes referred to as the fossils of our Solar System, Trojan asteroids are relatively untouched remnants of our primordial disk due to their unique orbital stability. Therefore, the physical characteristics of these populations can provide a window into the formation of our planets. This resonance relationship also means that Trojan asteroids are tied to the evolution of the planet’s orbit and can be used to constrain planetary migration models. Neptune’s Trojans (NTs) are particularly puzzling; while we would expect them to have colors similar to the Trans-Neptunian Object population, which is comprised of red and ultra-red objects, only one ultra-red NT has been found to date. We present the results of a complete photometric survey of the known NT population using the Magellan Baade 6.5m telescope. Our findings indicate that there are more ultra-red Neptune Trojans than previously thought, suggesting that they may have indeed originated from the same source as ultra-red Trans-Neptunian objects, potentially resolving the “Trojan Color Conundrum”. Our upcoming JWST spectroscopic survey of Neptune Trojans will provide further insights into surface ice composition of these irradiated fossils.