A Comparison of Geminid Models with the PSP/WISPR-observed Phaethon Dust Trail

Abstract White-light observations from the Wide-Field Imager for Parker Solar Probe (WISPR) instrument on NASA’s Parker Solar Probe recently revealed the presence of a narrow, dense dust trail close to the orbit of asteroid 3200 Phaethon. Although Geminid related, it aligns imperfectly with Phaethon’s orbit and known Geminid meteoroid orbits. To address the nature of this dust trail, we performed a detailed comparison between the WISPR trail observations and several well-developed Geminid models. Simulating these models in the WISPR field of view visually demonstrates that the WISPR trail almost certainly represents the true “density core” of the Geminid stream. Trends in model trail width and offset from Phaethon’s orbit, both as functions of true anomaly, agree with observations to varying extents. All the models, however, place their apparent core interior to the parent orbit due to Poynting–Robertson forces, contradictory to the WISPR trail, which is exterior to Phaethon’s orbit. Therefore, Phaethon’s current orbit likely does not represent the orbit of the system parent, which most probably had a larger semimajor axis. These findings provide new initial conditions for future Geminid models, with WISPR identifying the Geminid core’s position.