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Session 72 - Comet Hale-Bopp.
Display session, Friday, January 09
Exhibit Hall,

[72.05] Infrared Observations of the Dust in Comet Hale-Bopp

C. M. Lisse, Y. R. Fernandez, M. F. A'Hearn (U. Maryland), T. Kostiuk, T. A. Livengood (NASA/GSFC), H. U. Käufl (ESO-Garching), W. F. Hoffmann, A. Dayal (U. Arizona), 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 static 6 to 8 jet "hedgehog" structure in 1996 to the rotating "pinwheel" structure seen in 1997. Light curves taken at perihelion indicate a rotational periodicity of 11.3 hours. The comet was found to be exteremly dusty, with a dust/gas the Dust ratio of 8 and an extremely strong silicate emission feature

We present dust production rates, particle size distribu- tions and compositions found by fitting fluffy Mie dust models to the multi-wavelength photometry. We also present estimates for the dust outflow rate and constraints on the rotation state of the nucleus from imaging of the comet over time.

Program listing for Friday