Rotational Period Investigation of Comet P/Tempel 2 During the 1999 Apparition and Other Results (original) (raw)

2010

Abstract

Thirty-one nights of broadband R and narrowband photometry were obtained of 10P/Tempel during its 1999/2000 apparition using Lowell Observatory 1.1 and 1.8-m telescopes. Early emphasis was placed on obtaining rotational lightcurves, while narrowband measurements later in the apparition were intended to study coma morphology. From our broadband measurements we determine a double-peaked rotation period of 8.938 hrs with an uncertainty of ±0.002 hours. Mueller and Ferrin (1996) suggested a possible change in Tempel 2's rotation period from the 1988 to the 1994 apparitions, comparing five possible rotation periods from data obtained in October and December of 1994 to Sekanina's (1991) period of 8.932 hours determined for the 1988 apparition. We can conclusively rule out four of Mueller and Ferrin's five periods, leaving their period of 8.939, which is within the uncertainty of our period. It is important to note that Mueller and Ferrin's data were obtained post-perihelion during the 1994 apparition, and our 1999 data were obtained pre-perihelion. (If one presumes any change in period would be caused by gas jet-induced torques, it is reasonable to assume the period remains relatively unchanged between perihelion passages.) Two perihelion passages occurred between the 1988 and 1994 and 1999 data sets, suggesting a spin-down of Tempel 2's rotation rate of about 11 seconds per apparition. We present these results and others. This research was supported by NSF grant AST-0453611 and by the NASA Planetary Astronomy Program.

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