The Dust Tail of Asteroid (3200) Phaethon

TL;DR

This paper reports the discovery of a comet-like dust tail on asteroid Phaethon near perihelion, caused by small dust particles likely produced by thermal fracture, confirming its activity and link to Geminid meteoroids.

Contribution

First direct imaging of a dust tail on Phaethon near perihelion, revealing active dust ejection caused by thermal processes.

Findings

Dust tail extends over 350 arcseconds in anti-solar direction.

Dust particles are approximately 1 micrometer in radius.

Estimated dust mass is about 3x10^5 kg.

Abstract

We report the discovery of a comet-like tail on asteroid (3200) Phaethon when imaged at optical wavelengths near perihelion. In both 2009 and 2012, the tail appears >=350" (2.5x10^8 m) in length and extends approximately in the projected anti-solar direction. We interpret the tail as being caused by dust particles accelerated by solar radiation pressure. The sudden appearance and the morphology of the tail indicate that the dust particles are small, with an effective radius ~1 micrometer and a combined mass ~3x10^5 kg. These particles are likely products of thermal fracture and/or desiccation cracking under the very high surface temperatures (~1000 K) experienced by Phaethon at perihelion. The existence of the tail confirms earlier inferences about activity in this body based on the detection of anomalous brightening. Phaethon, the presumed source of the Geminid meteoroids, is still active.