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K. Barnes (Franklin and Marshall College), N. Baugh (LPL, University of Arizona), D. Schleicher (Lowell Observatory), L. Woodney (CSU San Bernardino)
We present broadband and narrowband imaging results of Comet 9P/Tempel 1 throughout the early apparition and with greater emphasis during the encounter of Deep Impact. Observations from Lowell Observatory began in March 2005 to characterize gas and dust morphology as a function of our viewing geometry and cometary season. Pre-impact dust images show a persistent fan with possible rotational variation evident by early June. Continuum subtracted CN images also show a fan of jet material, spatially independent from the dust fan, and a more distinct nightly variation due to nucleus rotation. Subsequently, a 10 night observing campaign surrounding the collision of DI began on July 1st to study the effects of material ejected from impact. At the time of impact no fireball was detected. Prominent post-impact brightening from ejecta material continued for over an hour after impact with a slow, corresponding decrease in optical depth. We have successfully reproduced both the general morphology of the ejcta plume and many details of the shape and brightness distribution on successive nights following the impact using a modified Monte Carlo jet model, with an initial impulse event in the shape of an open, thick-walled cone. Derived from the model, ejecta material had an initial outflow velocity of less than 0.23 km/s and particle sizes less than 2.5 microns (assuming compact grains). These small particle sizes and large velocities resulted in the rapid development of a dust tail composed of ejecta particles being pushed away from the Sun via radiation pressure. In nearly all respects, Comet Tempel 1 returned to pre-impact conditions only 6 days after the event.
Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.