PI: Karen Meech, University of Hawaii (IfA), firstname.lastname@example.org
Address: Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822, USA
CoI: Olivier Hainaut, European Southern Observatory
CoI: Dina Prialnik, Tel Aviv University
CoI: Gal Sarid, UH after 10/22/09
Title: Investigating the Early Solar System with Distant Comet Nuclei
Abstract: We request 6 half nights on Gemini S (classical preferred, queue acceptable) with GMOS to get very deep images for 6 long period and dynamically new comets for which we have a 15 year database of imaging observations as a function of heliocentric distance. We have just completed 65 orbits of HST imaging on these targets in order to get their nucleus sizes. We will use the GMOS observations to make deep composite images down to 27-28 mag/arcsec^2 in order to assess how much dust is around the nuclei to get final constraints on activity / dust production for thermal modeling and to enable us to remove it from the HST images and get the best estimate of nucleus size. Observations for 5 comets for which we previously had nucleus size estimates have been combined with quasi-3D thermal models. The results suggest that the comets fall into 2 classes, possibly representing different internal microphysical structures which can be related to differences in formation conditions within the protosolar nebula. The purpose of the 2009 HST program was to utilize HTS's superb resolution to get measurements for an additional 8 well-observed comet nuclei, essential inputs to the thermal models. Some comets were found to still be active (possessing dust comae) even at large distances (14-28 AU). We require deep GMOS images to search for low surface brightness dust comae (indicating current or activity) (1) to remove it from the HST images to get reliable nucleus sizes and (2) to determine if the comets are still active and to use dust dynamical models to determine boundary conditions for our thermal models.
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