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Small particles dominate Saturn’s Phoebe ring to surprisingly large distances

Hamilton, Douglas P. and Skrutskie, Michael F. and Verbiscer, Anne J. and Masci, Frank J. (2015) Small particles dominate Saturn’s Phoebe ring to surprisingly large distances. Nature, 522 (7555). pp. 185-187. ISSN 0028-0836.

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Saturn’s faint outermost ring, discovered in 2009, is probably formed by particles ejected from the distant moon Phoebe. The ring was detected between distances of 128 and 207 Saturn radii (R_S = 60,330 kilometres) from the planet, with a full vertical extent of 40R_S, making it well over ten times larger than Saturn’s hitherto largest known ring, the E ring. The total radial extent of the Phoebe ring could not, however, be determined at that time, nor could particle sizes be significantly constrained. Here we report infrared imaging of the entire ring, which extends from 100R_S out to a surprisingly distant 270R_S. We model the orbital dynamics of ring particles launched from Phoebe, and construct theoretical power-law profiles of the particle size distribution. We find that very steep profiles fit the data best, and that elevated grain temperatures, arising because of the radiative inefficiency of the smallest grains, probably contribute to the steepness. By converting our constraint on particle sizes into a form that is independent of the uncertain size distribution, we determine that particles with radii greater than ten centimetres, whose orbits do not decay appreciably inward over 4.5 billion years, contribute at most about ten per cent to the cross-sectional area of the ring’s dusty component.

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Masci, Frank J.0000-0002-8532-9395
Additional Information:© 2015 Macmillan Publishers Limited. Received 31 October 2014; Accepted 2 April 2015. This publication makes use of data products from the Wide field Infrared Survey Explorer, which is a joint project of the University of California, Los Angeles, and the Jet Propulsion Laboratory/California Institute of Technology, funded by the National Aeronautics and Space Administration. This research was supported by grants from NASA Outer Planets and Origins (D.P.H.). Author Contributions: F.J.M. led the development of the WISE Image Atlas products and provided optimally background-matched custom mosaics to support this analysis. M.F.S. and A.J.V. did the image processing and data analysis associated with Figs 1 and 2. D.P.H. performed the analytic calculations, ran the numerical models, and produced the theoretical curves of Figs 3 and 4.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Issue or Number:7555
Record Number:CaltechAUTHORS:20150706-113942909
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Official Citation:Hamilton, D. P., Skrutskie, M. F., Verbiscer, A. J., & Masci, F. J. (2015). Small particles dominate Saturn/'s Phoebe ring to surprisingly large distances. [Letter]. Nature, 522(7555), 185-187. doi: 10.1038/nature14476
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:58777
Deposited By: Joanne McCole
Deposited On:06 Jul 2015 21:29
Last Modified:05 May 2020 18:57

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