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A statistical review of light curves and the prevalence of contact binaries in the Kuiper Belt

Showalter, Mark R. and Benecchi, Susan D. and Buie, Marc W. and Grundy, William M. and Keane, James T. and Lisse, Carey M. and Olkin, Cathy B. and Porter, Simon B. and Robbins, Stuart J. and Singer, Kelsi N. and Verbiscer, Anne J. and Weaver, Harold A. and Zangari, Amanda M. and Hamilton, Douglas P. and Kaufmann, David E. and Lauer, Tod R. and Mehoke, D. S. and Mehoke, T. S. and Spencer, J. R. and Throop, H. B. and Parker, J. W. and Stern, S. Alan (2021) A statistical review of light curves and the prevalence of contact binaries in the Kuiper Belt. Icarus, 356 . Art. No. 114098. ISSN 0019-1035.

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We investigate what can be learned about a population of distant Kuiper Belt Objects (KBOs) by studying the statistical properties of their light curves. Whereas others have successfully inferred the properties of individual, highly variable KBOs, we show that the fraction of KBOs with low amplitudes also provides fundamental information about a population. Each light curve is primarily the result of two factors: shape and orientation. We consider contact binaries and ellipsoidal shapes, with and without flattening. After developing the mathematical framework, we apply it to the existing body of KBO light curve data. Principal conclusions are as follows. (1) When using absolute magnitude H as a proxy for the sizes of KBOs, it is more accurate to use the maximum of the light curve (minimum H) rather than the mean. (2) Previous investigators have noted that smaller KBOs tend to have higher-amplitude light curves, and have interpreted this as evidence that they are systematically more irregular in shape than larger KBOs; we show that a population of flattened bodies with uniform proportions, independent of size, could also explain this result. (3) Our method of analysis indicates that prior assessments of the fraction of contact binaries in the Kuiper Belt may be artificially low. (4) The pole orientations of some KBOs can be inferred from observed changes in their light curves over time scales of decades; however, we show that these KBOs constitute a biased sample, whose pole orientations are not representative of the population overall. (5) Although surface topography, albedo patterns, limb darkening, and other surface properties can affect individual light curves, they do not have a strong influence on the statistics overall. (6) Photometry from the Outer Solar System Origins Survey (OSSOS) survey is incompatible with previous results and its statistical properties defy easy interpretation. We also discuss the promise of this approach for the analysis of future, much larger data sets such as the one anticipated from the upcoming Vera C. Rubin Observatory.

Item Type:Article
Related URLs:
URLURL TypeDescription ItemData
Buie, Marc W.0000-0003-0854-745X
Keane, James T.0000-0002-4803-5793
Lisse, Carey M.0000-0002-9548-1526
Weaver, Harold A.0000-0003-0951-7762
Lauer, Tod R.0000-0003-3234-7247
Mehoke, D. S.0000-0002-7698-2026
Mehoke, T. S.0000-0001-6607-8925
Parker, J. W.0000-0002-3672-0603
Additional Information:© 2020 Published by Elsevier. Received 25 November 2019, Revised 30 August 2020, Accepted 1 September 2020, Available online 9 September 2020. This work was funded by NASA's New Horizons project. Coauthor Benecchi also acknowledges support for this work under NASA Grant/Contract/Agreement No. NNX15AE04G issued through NASA's SSO Planetary Astronomy Program. Data Availability: The software library used to generate the 3-D shapes and light curve models appearing in this article was written by lead author Showalter and is permanently archived at Additional documentation, sample programs and data files are also provided. Author contributions: This work emerged from the approach-phase observations for the New Horizons flyby of (486958) 2014 MU69 Arrokoth; all the named coauthors participated in the planning, analysis and scientific discussions surrounding this activity. Declaration of Competing Interest: None.
Funding AgencyGrant Number
Subject Keywords:Kuiper belt; Transneptunian objects; Photometry; Rotational dynamics
Record Number:CaltechAUTHORS:20200911-133136792
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Official Citation:Mark R. Showalter, Susan D. Benecchi, Marc W. Buie, William M. Grundy, James T. Keane, Carey M. Lisse, Cathy B. Olkin, Simon B. Porter, Stuart J. Robbins, Kelsi N. Singer, Anne J. Verbiscer, Harold A. Weaver, Amanda M. Zangari, Douglas P. Hamilton, David E. Kaufmann, Tod R. Lauer, D.S. Mehoke, T.S. Mehoke, J.R. Spencer, H.B. Throop, J.W. Parker, S. Alan Stern, A statistical review of light curves and the prevalence of contact binaries in the Kuiper Belt, Icarus, Volume 356, 2021, 114098, ISSN 0019-1035, (
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:105345
Deposited By: George Porter
Deposited On:12 Sep 2020 15:07
Last Modified:08 Jan 2021 18:11

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