DPS 2001 meeting, November 2001
Session 20. Comet Posters
Displayed, 9:00am Tuesday - 3:00pm Saturday, Highlighted, Wednesday, November 28, 2001, 10:30am-12:30pm, French Market Exhibit Hall

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[20.06] Aphelion Activity of 2P/Encke

K. J. Meech, Y. Fernández, J. Pittichová (IfA)

As part of a long-term observing campaign to look at the activity in distant comets, data have been obtained on a number of short-period comets for comparison. Here we present the data for comet 2P/Encke, the first CONTOUR mission target, from 1985 through the present, sampling 6 apparitions. The comet nucleus has a color which is typical of other short period comets, all of which lie in the range from mV-mR = 0.3-0.6 mag. Its coma is particularly lacking in micron-sized grains when beyond 2 AU from the Sun; the dust coma is hardly apparent at visible wavelengths. Heliocentric light curves, however, indicate that the comet is definitely active near every aphelion, sometimes appearing as many as 2 magnitudes brighter intrinsically. The comet never shows an extended coma near aphelion so all the dust is confined to the seeing disk, presumably in the form of large, slow-moving grains. We will present heliocentric data from the last six apparitions, limits on the aphelic dust production, and speculation on the physical mechanism behind the phenomenon.

This work was supported by NASA Grants NAGW-5015 and NAG5-4495.

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