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Discovery of a Makemakean MoonWe describe the discovery of a satellite in orbit about the dwarf planet (136472) Makemake. This satellite, provisionally designated S/2015 (136472) 1, was detected in imaging data collected with the Hubble Space Telescope's Wide Field Camera 3 on UTC 2015 April 27 at 7.80 +/- 0.04 mag fainter than Makemake and at a separation of 0farcs57. It likely evaded detection in previous satellite searches due to a nearly edge-on orbital configuration, placing it deep within the glare of Makemake during a substantial fraction of its orbital period. This configuration would place Makemake and its satellite near a mutual event season. Insufficient orbital motion was detected to make a detailed characterization of its orbital properties, prohibiting a measurement of the system mass with the discovery data alone. Preliminary analysis indicates that if the orbit is circular, its orbital period must be longer than 12.4 days and must have a semimajor axis > or approx. = 21,000 km. We find that the properties of Makemake's moon suggest that the majority of the dark material detected in the system by thermal observations may not reside on the surface of Makemake, but may instead be attributable to S/2015 (136472) 1 having a uniform dark surface. This dark moon hypothesis can be directly tested with future James Webb Space Telescope observations. We discuss the implications of this discovery for the spin state, figure, and thermal properties of Makemake and the apparent ubiquity of trans-Neptunian dwarf planet satellites.
Document ID
Document Type
Reprint (Version printed in journal)
Parker, Alex H. (Southwest Research Inst. Boulder, CO, United States)
Buie, Marc W. (Southwest Research Inst. Boulder, CO, United States)
Grundy, Will M. (Lowell Observatory Flagstaff, AZ, United States)
Noll, Keith S. (NASA Goddard Space Flight Center Greenbelt, MD United States)
Date Acquired
June 29, 2017
Publication Date
June 27, 2016
Publication Information
Publication: The Astrophysical Journal Letters
Volume: 825
Issue: 1
ISSN: 2041-8205
Subject Category
Report/Patent Number
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