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

TL;DR

This study updates observations of a dust trail linked to asteroid Phaethon using WISPR on PSP, revealing that the dust trail does not exactly follow Phaethon's orbit and varies with true anomaly.

Contribution

It provides new observational data over multiple encounters, showing the dust trail's deviation from Phaethon's orbit and refining dust mass estimates.

Findings

Dust trail does not perfectly follow Phaethon's orbit.

Estimated dust mass ranges from 10^10 to 10^12 kg.

Trail deviation increases with true anomaly.

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 Parker Solar Probe (WISPR) instrument on the NASA Parker Solar Probe (PSP) mission. Here we provide a summary and analysis of observations of the dust trail over nine separate mission encounters between October 2018 and August 2021 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 inline with those in the initial publication, with a visual (V) magnitude of approximately 16.1$\pm$0.3 per pixel, corresponding to a surface brightness of 26.1 mag arcsec$^{-2}$, and an estimated mass of dust within the range $10^{10}$ kg - $10^{12}$ 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-degree in periapsis.