In Search of Recent Disruption of (3200) Phaethon: Model Implication and Hubble Space Telescope Search

TL;DR

This study used Hubble Space Telescope observations and numerical simulations to investigate recent activity and dust ejection from asteroid (3200) Phaethon, finding no recent large fragments and setting limits on its mass loss and dust flux.

Contribution

The paper provides the first direct search for meter-sized fragments near Phaethon and constrains its recent mass loss and dust flux through combined observational and simulation approaches.

Findings

No meter-sized fragments detected near Phaethon.

Limits set on Phaethon's recent mass loss at 10^12 kg.

Dust flux near Phaethon is below 10^{-12} m^{-2} s^{-1}.

Abstract

Near-Earth asteroid (3200) Phaethon is notable for its association to a strong annual meteor shower, the Geminids, indicative of one or more episodes of mass ejection in the past. The mechanism of Phaethon's past activity is not yet understood. Here we present a Hubble Space Telescope (HST) search of meter-sized fragments in the vicinity of Phaethon, carried out during Phaethon's historic approach to the Earth in mid-December of 2017. Numerical simulation conducted to guide HST's pointing also show that the dynamical evolution of Phaethon-originated particles is quick, as ejected materials take no longer than $\sim250$ yr to spread to the entire orbit of Phaethon. Our search was completed down to 4-meter-class limit (assuming Phaethon-like albedo) and was expected to detect 0.035% particles ejected by Phaethon in the last several decades. The negative result of our search capped the total mass loss of Phaethon over the past few dozen orbits to be $10^{12}$ kg at $3\sigma$ level, taking the best estimates of size power-law from meteor observations and spacecraft data. Our result also implies a millimeter-sized dust flux of $<10^{-12} \mathrm{m^{-2} s^{-1}}$ within 0.1 au of Phaethon, suggesting that any Phaethon-bound mission is unlikely to encounter dense dust clouds.