@article{e141daa9c09d4367bac426131e92f021,
title = "The orbit, mass, size, albedo, and density of (65489) Ceto/Phorcys: A tidally-evolved binary Centaur",
abstract = "Hubble Space Telescope observations of Uranus- and Neptune-crossing object (65489) Ceto/Phorcys (provisionally designated 2003 FX128) reveal it to be a close binary system. The mutual orbit has a period of 9.554 ± 0.011 days and a semimajor axis of 1840 ± 48 km. These values enable computation of a system mass of (5.41 ± 0.42) × 1018 kg. Spitzer Space Telescope observations of thermal emission at 24 and 70 μm are combined with visible photometry to constrain the system's effective radius (109-11+10 km) and geometric albedo (0.084-0.014+0.021). We estimate the average bulk density to be 1.37-0.32+0.66 g cm-3, consistent with ice plus rocky and/or carbonaceous materials. This density contrasts with lower densities recently measured with the same technique for three other comparably-sized outer Solar System binaries (617) Patroclus, (26308) 1998 SM165, and (47171) 1999 TC36, and is closer to the density of the saturnian irregular satellite Phoebe. The mutual orbit of Ceto and Phorcys is nearly circular, with an eccentricity ≤0.015. This observation is consistent with calculations suggesting that the system should tidally evolve on a timescale shorter than the age of the Solar System.",
keywords = "Centaurs, Kuiper belt, Satellites, Trans-neptunian objects",
author = "Grundy, {W. M.} and Stansberry, {J. A.} and Noll, {K. S.} and Stephens, {D. C.} and Trilling, {D. E.} and Kern, {S. D.} and Spencer, {J. R.} and Cruikshank, {D. P.} and Levison, {H. F.}",
note = "Funding Information: This work is based in part on NASA/ESA Hubble Space Telescope Cycle 14 program 10508 and 10514 observations. Support for these programs was provided by NASA through a grant from the Space Telescope Science Institute (STScI), which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA Contract NAS 5-26555. We are especially grateful to Tony Roman and Tricia Royle at STScI for their rapid reactions in scheduling the HST follow-up observations. STSDAS and PyRAF are products of STScI. This work is also based in part on Spitzer Space Telescope Cycle 3 program 30081 observations. Spitzer is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA through an award issued by JPL/Caltech. We thank two anonymous reviewers for numerous constructive suggestions on how to improve this manuscript. Finally, we are grateful to the free and open source software communities for empowering us with many of the tools used to complete this project, notably Linux, the GNU tools, OpenOffice.org, MySQL, FVWM, Python, IRAF, STSDAS, PyRAF, and TkRat. ",
year = "2007",
month = nov,
doi = "10.1016/j.icarus.2007.04.004",
language = "English (US)",
volume = "191",
pages = "286--297",
journal = "Icarus",
issn = "0019-1035",
publisher = "Academic Press Inc.",
number = "1",
}