An Upper Limit on Gas Production from 3200 Phaethon

TL;DR

This study sets upper limits on gas production from asteroid 3200 Phaethon, which resembles a comet but shows no detectable gas emissions despite observations near perihelion.

Contribution

It provides the first observational upper limits on gas production from Phaethon, enhancing understanding of its comet-like behavior and activity levels.

Findings

No detectable CO emission was observed.

Upper limits on CO production were established.

Phaethon exhibits no significant gas activity near perihelion.

Abstract

Asteroid 3200 Phaethon resembles a comet in some ways, including a highly-eccentric orbit (e=0.89) and a strong associated meteor shower (the Geminids). Yet this object has never been observed to exhibit any cometary activity, i.e., gas production. We observed 3200 Phaethon with the Caltech Submillimeter Observatory on two occasions, once while it was near its closest approach to Earth as it neared perihelion, and another while it was further from Earth post-perihelion. Observations of the J=2-1 and J=3-2 rotational transitions of 12CO, typically strong lines in comets and indicative of gas production, yielded no detection. Upper limits on the 12CO production of 1.8e28 molecules/s and 7.6e28 molecules/s for Phaethon were determined on these two occasions.