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M. S. Kelley, C. E. Woodward, R. D. Gehrz (U Minn.), W. T. Reach (SSC/Caltech)
Comet dust trails are the long lived, large particle remnants of cometary mass loss episodes. These particles (sizes of order 1 mm or larger) remain in an orbit similar to the parent comet unless they are perturbed by planetary interactions that do not affect the comet nucleus. The Jupiter-family comet 2P/Encke has a very stable orbit and this is reflected by its extensive dust trail as observed by IRAS [1].
We present Spitzer IRAC, MIPS, and IRS observations of comet 2P/Encke from June 2004, six months after perihelion. Images show a prominent dust jet and dust trail similar to the Reach et al.\ [2] July 1997 ISO observation (2 months post-perihelion) and more detailed than the Epifani et al.\ [3] October 1997 ISO observation (5 months post-perihelion). Spectra show no silicate feature, as expected for a comet which mostly releases large particles. We present model images of the dust distribution produced with our own dynamical model employing a Monte-Carlo technique. We use this model to discuss the size and ejection velocity of particles leaving the nucleus.
References: [1] M.~V.\ Sykes and R.~G.\ Walker (1992), Icarus, 95, 180, 1992; [2] W.~T.\ Reach et al.\ (2000), Icarus, 148, 80; [3] E.~Epifani et al.\ (2001), Icarus, 149, 339.
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Bulletin of the American Astronomical Society, 36 5
© 2004. The American Astronomical Society.