Name:	Kramer, Emily
Email:	emily.kramer@jpl.nasa.gov
Institution:	JPL
Title:	Cometary Dust Tails in NEOWISE
Topic:	Time Domain
Abstract:	NEOWISE is the planetary-funded mission that utilizes data from the Wide-Field Infrared Survey Explorer (WISE) spacecraft to detect and characterize moving objects. During the course of the prime mission, over 160 comets were serendipitously observed, including 22 newly discovered comets. About 89 of the comets observed by NEOWISE displayed a significant dust tail in the 12 and 22-micron (thermal emission) bands, showing a wide range of activity levels and dust morphology. Since the observed objects are a mix of both long-period comets (LPCs) and short-period comets (SPCs), differences in their activity can be used to better understand the thermal evolution that each of these populations has undergone. For the comets that displayed a significant dust tail, we have estimated the sizes and ages of the particles using dynamical models based on the Finson-Probstein method. For a selection of 40 comets, we have then compared these models to the data using a novel tail-fitting method that allows the best-fit model to be chosen analytically rather than subjectively. For comets that were observed multiple times by WISE, the dust tail particle properties were estimated separately, and then compared. We find that the dust tails of both LPCs and SPCs are primarily comprised of ~mm to cm sized particles, which were the result of emission that occurred several months to several years prior to the observations. The LPCs nearly all have strong dust emission close to the comet's perihelion distance, and the SPCs mostly have strong dust emission close to perihelion, but some have strong dust emission well before perihelion. Since the restart of NEOWISE in late 2013, over 60 comets have been observed in the 3.4 and 4.6-micron bands, including a mix of both SPCs and LPCs and three (as of early December 2014) newly discovered comets. As during the prime mission, the comets seen by NEOWISE have a wide range of activity levels, dust morphology, and gas morphology over a wide range of heliocentric distances. We will showcase some preliminary results from the new data, highlighting several interesting cases.