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A. L. Cochran (U. Texas, McDonald Obs.)
During 2003, comet 2P/Encke made a close pass to the Earth (0.26 AU), allowing for excellent viewing of this comet. We used the facilities of The University of Texas McDonald Observatory to obtain extensive coverage of the apparition. On 25 September and 22--24 October, we observed Encke with a long-slit CCD spectrograph at Cassegrain of the 2.7m telescope, using a resolving power R=\lambda/\Delta\lambda=500 and a bandpass from 3000--5600Å. During the October time period, the slit was rotated to many position angles to map the distribution of gas in the coma. On 4--5 November, 11--12 November and 18--19 November, we used the coudé focus of the 2.7m telescope at R=60,000 to observe the bandpass from 3700--10,100Å\ and study the lines in detail. We obtained long-slit Cassegrain spectra at R=2,200 of the OH and NH region on 25--28 November in order to study the Greenstein effect. We present the results of these observing runs.
The data will allow a detailed look at the gas in the coma. The comet displays a remarkable decline in gas on the tailward side, such that very little gas is seen even 10,000 km from the nucleus. In contrast, the gas has a much higher column density on the sunward side, where a forward-facing fan-shaped coma is seen. We will display broad-band images obtained the same night for comparison with the spectral results.
The data were obtained under NASA Grant NAG5 19617.
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Bulletin of the American Astronomical Society, 36 #4
© 2004. The American Astronomical Soceity.