NOAO >   Observing Info >   Approved Programs >   2013A-0435

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Proposal Information for 2013A-0435


PI: Anne Verbiscer, University of Virginia, verbiscer@virginia.edu
Address: Department of Astronomy, PO Box 400325, Charlottesville, VA, 22904-4325, USA

CoI: Will Grundy, Lowell Observatory
CoI: Susan Benecchi, Carnegie Institution of Washington (Terrestrial Magn.)
CoI: David Rabinowitz, Yale University

Title: Mutual Event of Transneptunian Binary (79360) Sila-Nunam

Abstract: The transneptunian binary (79360) Sila-Nunam (provisionally designated 1997 CS29) is currently undergoing mutual events in which the two nearly-equal brightness components alternate in eclipsing and occulting each other as seen from Earth (Grundy et al. 2012, Verbiscer et al. 2012a). The low eccentricity of the orbit, determined from Hubble Space Telescope observations of the resolved components (Grundy et al. 2012), and the coincidence of the system's photometric lightcurve and orbital period are consistent with a system that is tidally locked and synchronized, like that of Pluto-Charon. Mutual events provide a rich opportunity to learn about size, shape, color, and albedo patterns on the system components. Mutual events of Pluto-Charon observed between 1985-1990 provided the first characterization of their albedo distributions. The duration of the mutual event season depends on the size and separation of the system components. Using sizes determined from thermal observations, the mutual event season for Sila-Nunam should last about a decade; however, the deepest, most central (and thus most informative) events are predicted to be observable in the 2013 apparition, with progressively shallower events observable thereafter for the next 4-5 years. Gemini-North is ideally located to observe a complete mutual event of Sila-Nunam which begins at 5:59 UT on 14 February 2013 and ends at 14:17. Since Sila-Nunam will be near opposition, the target is visible to GMOS for the entire night. This event is a rare opportunity to determine the size, density, and albedo/color patterns on a primitive body which has likely been unaltered since the time of Solar System formation.


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NOAO >   Observing Info >   Approved Programs >   2013A-0435

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