MUSE observations of comet 67P/Churyumov-Gerasimenko: A reference for future comet observations with MUSE

TL;DR

This study used MUSE to observe comet 67P at large distances, providing a spectral and spatial reference for future comet observations, including dust properties, jets, and water production rates.

Contribution

It presents the first high-quality optical spectrum of 67P's dust coma and introduces a novel method to detect gas emissions combining spectral and spatial data.

Findings

Dust reflectivity slope of 10%/100 nm from 480-900 nm

Measured dust production rates in V, R, and I bands

Detected water production rate of approximately 1.5×10^{26} molecules/sec

Abstract

Observations of comet 67P/Churyumov-Gerasimenko were performed with MUSE at large heliocentric distances post-perihelion, between March 3 and 7, 2016. Those observations were part of a simultaneous ground-based campaign aimed at providing large-scale information about comet 67P that complement the ESA/Rosetta mission. We obtained a total of 38 datacubes over 5 nights. We take advantage of the integral field unit (IFU) nature of the instrument to study simultaneously the spectrum of 67P's dust and its spatial distribution in the coma. We also look for evidence of gas emission in the coma. We produce a high quality spectrum of the dust coma over the optical range that could be used as a reference for future comet observations with the instrument. The slope of the dust reflectivity is of 10%$/100$ nm over the 480-900 nm interval, with a shallower slope towards redder wavelengths. We use the $\mathrm{Af\rho}$ to quantify the dust production and measure values of 65$\pm$4 cm, 75$\pm$4 cm, and 82$\pm$4 cm in the V, R, and I bands respectively. We detect several jets in the coma, as well as the dust trail. Finally, using a novel method combining spectral and spatial information, we detect the forbidden oxygen emission line at 630 nm. Using this line we derive a water production rate of $1.5\pm0.6 \times 10^{26} \mathrm{molec./s}$, assuming all oxygen atoms come from the photo-dissociation of water.