Continued PSP/WISPR Observations of a Phaethon-related Dust Trail

Abstract

We present an update to the first white-light detections of a dust trail observed closely following the orbit of asteroid (3200) Phaethon, as seen by the Wide-field Imager for the Parker Solar Probe instrument on the NASA Parker Solar Probe mission. Here, we provide a summary and analysis of observations of the dust trail over nine separate mission encounters between 2018 October and 2021 August that saw the spacecraft approach to within 0.0277 au of the orbit of Phaethon. We find the photometric and estimated dust mass properties to be in line with those in the initial publication, with a visual (V) magnitude of V ∼ 16.1 ± 0.3 pixel−1, corresponding to a surface brightness of 26.1 mag arcsec−2, and an estimated mass of dust within the range 1010–1012 kg depending on the assumed dust properties. However, the key finding of this survey is the discovery that the dust trail does not perfectly follow the orbit of Phaethon, with a clear separation noted between them that increases as a function of true anomaly, though the trail may differ from Phaethon’s orbit by as little as 1° in periapsis.