Infrared Observations of the Dust Emitted by Comet Hale-Bopp

C. M. Lisse, Y. R. Fernández, M. F. A'Hearn (U.Md.), T. Kostiuk, T. A. Livengood (NASA/GSFC), H.U. Kaufl (ESO-Garching), W. F. Hoffmann, A. Dayal (U.Az.), L. K. Deutsch (Bos.U.), G. G. Fazio (CfA), J. L. Hora (IfA), M. S. Hanner, M. Ressler (JPL)

We present preliminary analyses of infrared imaging and photometry of the bright, giant comet C/1995 O1 (Hale-Bopp). The comet was observed in an extended campaign using the ESO 3.6m telescope with the TIMMI camera in October and December 1996, using the NASA/IRTF telescope with the MIRAC2 and MIRLIN cameras in January and April 1997 (near perihelion), and again at ESO using the TIMMI camera in July 1997.

The morphology of the comet was observed to change from the 6 to 8 jet "hedgehog" structure in 1996 to the "pinwheel" structure seen in 1997. Light curves taken at perihelion indicate a rotational periodicity of  11.3 hours. We present dust production rates, dust to gas ratios, and estimates for the particle size distribution and composition found by fitting fluffy Mie dust models to the multi-wavelength photometry.