MUSE observations of comet 67P/Churyumov-Gerasimenko

Abstract

Aims. Observations of comet 67P/Churyumov-Gerasimenko were performed with MUSE at large heliocentric distances post-perihelion between 3 and 7 March 2016. These observations are part of a simultaneous ground-based campaign aimed at providing broad-scale information about comet 67P to complement the ESA/Rosetta mission. Methods. We obtained a total of 38 datacubes over five nights. We took advantage of the integral field unit nature of the instrument to carry out a simultaneous study of the spectrum of 67P’s dust and its spatial distribution in the coma. We also looked for evidence of gas emission in the coma. Results. We produced a high-quality spectrum of the dust coma over the optical range that could be used as a reference for future comet observations with this 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 used the Afρ to quantify the dust production and measure values of 65 ± 4 cm, 75 ± 4 cm, and 82 ± 4 cm in the V, R, and I bands, respectively. We detected several jets in the coma as well as the dust trail. Finally, using a novel method combining spectral and spatial information, we detected the forbidden oxygen emission line at 630 nm. Using this line, we derived a water production rate of 1.5 ± 0.6 × 1026 molec. s−1, assuming all oxygen atoms come from the photo-dissociation of water.