PI: Beatrice Mueller, Planetary Science Institute, firstname.lastname@example.org
Address: 1700 E. Ft. Lowell Rd., Suite 106, Tucson, AZ 85719
CoI: Nalin Samarasinha, Planetary Science Institute
CoI: Yanga Fernandez, Univ. of Central Florida
Title: Continuing changes in the rotation period of comet 2P/Encke
Abstract: We propose to observe comet 2P/Encke for two runs in August and September, at least one month apart, to get high S/N photometry to construct high quality lightcurves to deduce an accurate rotation period. This period will be compared to those derived from previous apparitions; we have already found that the comet's rotation period is spinning down. We want to answer questions about how the rotation state is changing, e.g. is the change in rotation period constant from apparition to apparition? This has implications on the stability and longevity of the jets that drive the activity and the long-term evolution of the nucleus. We observed a difference in the rotation period between the 2008/2009 and the 2001/2002 apparitions of 0.14 hours (~8 min), which is much larger than the error bars or any synodic effects. As two perihelion passages occurred between these apparitions, the change in period is ~4 min per perihelion passage (if the change is constant). We request observing time to constrain the rate of change in the rotation period and to provide input to models of nucleus structure.
National Optical Astronomy Observatory, 950 North Cherry Avenue, P.O. Box 26732, Tucson, Arizona 85726, Phone: (520) 318-8000, Fax: (520) 318-8360