NOAO >   Observing Info >   Approved Programs >   2005B-0490

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Proposal Information for 2005B-0490


PI: Yanga Fernandez, University of Hawaii, yan@ifa.hawaii.edu
Address: Institute for Astronomy, 2680 Woodlawn Dr., Honolulu, HI 96822, U.S.A.

CoI: Stephen Lowry, Queen's University - Belfast
CoI: Beatrice Mueller, NOAO
CoI: Nalin Samarasinha, NOAO
CoI: Michael A'Hearn, Univ of Maryland
CoI: Tony Farnham, Univ of Maryland

Title: Search for Secular Drift in the Rotation of Comet 2P/Encke

Abstract: We propose to determine if and how the rotation state of Comet 2P/Encke changes from orbit to orbit. Time series of photometry in 2005, while the comet is near aphelion, will indicate if the dominant periodicity has changed from that measured around the previous aphelion, in 2001-2002. While it is possible that the comet is in non-principal axis rotation, one phenomenon that could also be present in the data is a secular drift of the rotation period caused by outgassing torques. The comet's emission of gas can provide a reaction force that could be spinning up the nucleus. Such a phenomenon must be taken into account if we are to understand P/Encke's rotation state. Furthermore this could be used to derive the comet's mass and density, fundamental properties that are poorly constrained among cometary nuclei. Comparison of data from the 1980s and the early 2000s suggests that the dominant periodicity is decreasing by about 2.4 minutes per orbit, but we need much more detailed coverage than what was obtained in the 1980s to be confident of this phenomenon's reality and magnitude.


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