A comprehensive numerical model has been developed to describe the interaction of light with cometary matter. The model simultaneously calculates the optical properties of large aggregated dust-particles, their thermally excited radiation and processes related to solid-state heat conduction and phase change. The model has been has been applied to interpret optical and near-infrared measurements by OSIRIS and VIRTIS. The measurements were found to be consistent with large aggregated particles composed of large silicate grains embedded in smaller carbon-rich grains.
To study the motion of debris emitted from comet 67P, two algorithms have been developed to track the motion of individual dust particles or boulders flying in the coma in either a series of short exposures, or a single long exposure. This paved the way to studying the source regions and ejection circumstances of the material.
Telescope time on Hubble and the Very Large Telescope of the European Southern Observatory has been awarded to project members to observe several active asteroids and comets. A multi-year series of Hubble observations allowed us to constrain the mutual orbit of the binary main-belt comet 288P and identify its active component, which has led to the serendipitous discovery of a third component to this system. Hubble images of interstellar comet 2I/Borisov led us to conclude that activity in this object was subject to both a diurnal and a seasonal cycle, similar to Rosetta target 67P.
These results are published in peer reviewed articles, e.g.
Markkanen et al. (2018), ApJ, 868, L16.
Markkanen & Agarwal (2019), A&A, 631, A164.
Markkanen & Agarwal (2020), A&A, 643, A16.
Kim et al. (2020), ApJL 895, L34.
Agarwal et al. (2020), A&A 643, A152.
Pfeifer et al. (2022), A&A, 659, A171.
Lemos et al. (2023), MNRAS 519, 5775.
