Mt. Wendelstein imaging of comet 41P/Tuttle-Giacobini-Kresak during the 2017 perihelion arc

Abstract

Context. In April 2017 comet 41P/Tuttle-Giacobini-Kresak (41P) passed perihelion close to Earth. Aims. We present observations of the comet and aim to use these to characterize its dust environment in the coma and of physical properties of the nucleus. Methods. 41P was imaged in the visible at the Mt. Wendelstein observatory over 45 nights between 2017 March 11 and 2017 July 17. Photometry of the coma provides information on the dust activity of the comet. Nucleus dimensions are determined by comparing radial profiles of observed images with those from models of the brightness distribution in the near-nucleus coma. Coma and tail structures in the images are enhanced using adaptive Laplace filtering and image normalization techniques. The geometry of the coma structures found are compared to results from dust models of the comet in order to obtain information on the nucleus rotation axis and the location of active regions on the nucleus. Results. Analyzing the evolution of the dust activity of the comet versus solar distance gives different results depending on the assumed phase angle corrections for the dust. Contamination from light emissions of the coma gas modified the colors in the coma and the slopes of the radial profiles. The light distribution in the very inner coma indicates some dust fragmentation close to the nucleus. The appearance of a prominent coma fan during the time period from March to May 2017 constrains the rotation axis of the nucleus (52 deg obliquity, 50 deg rotation angle of the perihelion meridian). This fan is produced by an extended region beyond about 50 deg latitude on the nucleus. Two narrow regions at low northern to equatorial latitudes were responsible for the time-variable occurrence of linear dust jets in the coma. An outburst of about 0.6 mag on 2017 May 11 generated various dust structures in the coma. The outburst originated from a region extending over a latitude range from +30 deg to −5 deg and released about 3000 tons of dust into the coma. The brightness of the nucleus indicates an equivalent radius of about 600 m and a minimum axis ratio larger than two.