The Period of Rotation, Shape, Density, and Homogeneous Surface Color of the Centaur 5145 Pholus

James Rall; S.C. Tegler; W. Romanishin; Raffaella De Vita; Raffaella De Vita; Raffaella De Vita; Raffaella De Vita

The Period of Rotation, Shape, Density, and Homogeneous Surface Color of the Centaur 5145 Pholus

ORAL

Abstract

We present optical photometry of the Centaur 5145 Pholus during 05/2003 and 04/2004 using the facility CCD camera on the 1.8-m VATT on Mt. Graham, Arizona. We derive a double-peaked lightcurve and a rotation period of 9.980 hr with amplitude of 0.60 magnitude. We derive four possible rotational pole positions as well as axial ratios of a/b=1.9 and c/b=0.9. If we assume Pholus is a strengthless rubble-pile and its non-spherical shape is due to rotational distortion, our axial ratios and period measurements indicate Pholus has a density of 0.5 g per cubic centimeter, suggestive of an ice-rich, porous interior. By combining B-band and R-band lightcurves, we find B-R=1.94 and any B-R color variation over the surface of Pholus must be smaller than 0.06 magnitudes. By combining our V-R measurements with values in the literature, we find no evidence for any color variegation between the northern and southern hemispheres of Pholus. Our observations add to the evidence that individual Centaurs and KBOs exhibit homogeneous surface colors and hence gray impact craters on radiation reddened crusts are probably not responsible for the colors seen among the Centaur and Kuiper belt object populations.

April 16, 2005, 1:54 PM – April 16, 2005, 2:06 PM

Authors

James Rall
S.C. Tegler

Northern Arizona University
W. Romanishin

University of Oklahoma
Raffaella De Vita

Kent State University, Jefferson Lab, Ohio University, Mainz University, Mainz, Germany, Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany, University of Washington, Noncommercial Partnership ``Scientific Instruments,'' Moscow, Russia, Lucent Technologies, North-West Technical University, St. Petersburg, Russia, Indiana University-Purdue University Indianapolis, Purdue University, University of Florida, Wabash College and Purdue University, University of Oregon, Garnett McKeen Lab, Inc., Korea Research Institute of Standards and Science, Daejeon, South Korea, 305-600, Department of Physics, Lab. of Solid State Microstructure, Nanjing University, Nanjing, 200008, China, Department of Physics, Hampton University, Hampton, VA 23668, NESB, NASA Langley Research Center, Hampton, VA 23681, Korea Research Institute of Stardards and Science, Daejeon, South Korea, 305-600, Department of Chemical Engineering, Sogang University, South Korea, 121-742, Indiana University, University of Chicago, LBNL, BNL/NSLS, KEK, Fermi National Accelerator Laboratory, LANL, University of Maryland, NIST, HMI, Harvard University, NCSU, Department of Physics and Astronomy, University of Nebraska, University of Southern California, University of California at Los Angeles, Stanford Linear Accelerator Center, Institute for Advanced Physics, Konkuk University, Korea, SUNY College at Oneonta, Department of Physics, University of Wisconsin-Whitewater, Whitewater WI 53190, Cyclotron Institute, Texas A\&M University, College Station, TX, University of Texas at El Paso, University of Buenos Aires, Cyclotron Institute, Texas A\&M University, College Station, TX 77843, Simon Bolivar University, Caracas, Venezuela, Warsaw University, Warsaw, Poland, Institut de Recherches Subatomiques, Strasbourg, France, Florida State University, Harvard-Smithsonian CfA, CENPA University of Washington, Pasadena City College, California State University, Northridge, California State University, Dominguez Hills, Chinese University of Hong Kong, Jet Propulsion Lab, California Institute of Technology, University of California, Irvine, Instituto de F\'isica, UNAM, University of Toronto, Friedrich-Schiller-Universitaet Jena, Pennsylvania State University, NIH, Stanford University, CNR, Italy, University of Texas, Austin, University of Nevada, Reno, University of Wisconsin-Madison, Hanseo University, Division of Materials Science and Technology, KIST, Seoul, 130-791, Korea, Department of Physics, Kangwon National University, Chuncheon, 200-701, Korea, Department of Techno-marketing, Mokwon University, Taejeon, 301-729, Korea, Institute of Physics and Applied Physics, Yonsei University, Seoul, 120-749, Korea, UNAM, Mexico, JINR, Dubna, Univ. of Notre-Dame, ANL, SUNY at Stony Brook, Lund U., ORNL, Washington U., Warsaw, Poland, Saclay, France, Boston University, National Institute for Standards and Technology, Boulder, Los Alamos National Laboratory, Yale University, Florida International University, MIT, Saint Mary's University, TRI-University Meson Facility, Institute of Nuclear Physics, Prague, Czech Republic, Institute of Physics and Nuclear Engineering, Bucharest, Romania, Cyclotron Institute, Texas A\&M Univ., Physics Division, Argonne National Laboratory, Wright Nuclear Structure Laboratory, Yale University, Tenn. Tech. Univ., Arizona State Univ., Ohio Univ., Tennessee Technologival Univ., ORNL Physics Division, Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, University of California, CEA, LLNL, Penn State Altoona, NC A&T State University, TUNL, NASA Langley Research Center, University of Iowa, UMD \& NASA/GSFC, NRC \& NASA/GSFC, NASA/GSFC, Academy at UAH, Oak Ridge National Laboratory, North Carolina State University, Union College, University of Hamburg, Iowa State University, Drake University, Lawrence Livermore National Laboratory, University of Arizona, UNC, Chapel Hill, NC, Tennessee Tech., Cookeville, TN, Rutgers Univ., New Brunswick, NJ, ORNL, Oak Ridge, TN, ORAU, Oak Ridge, TN, Collegium of Natural Sciences, Eckerd College, RIKEN (Institute of Physical and Chemical Research), Department of Physics, Rikkyo University, Department of Physics, University of Tokyo, Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University, Tokyo Inst. of Tech., Rikkyo Univ., Univ. of Tokyo, RIKEN, NSCL, Michigan State University, Dept. of Physics, University of Surrey, Guildford, UK, National Superconducting Cyclotron Laboratory, Michigan State University, University of Surrey, UK, IRES CNRS Strasbourg, Planetary Science Institute, Steward Observatory, University of Oklahoma, Vatican Observatory, University of Rochester, UIUC, Washington State University, Johns Hopkins University, Istituto Nazionale di Fisica Nucleare-Genova
Raffaella De Vita

Kent State University, Jefferson Lab, Ohio University, Mainz University, Mainz, Germany, Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany, University of Washington, Noncommercial Partnership ``Scientific Instruments,'' Moscow, Russia, Lucent Technologies, North-West Technical University, St. Petersburg, Russia, Indiana University-Purdue University Indianapolis, Purdue University, University of Florida, Wabash College and Purdue University, University of Oregon, Garnett McKeen Lab, Inc., Korea Research Institute of Standards and Science, Daejeon, South Korea, 305-600, Department of Physics, Lab. of Solid State Microstructure, Nanjing University, Nanjing, 200008, China, Department of Physics, Hampton University, Hampton, VA 23668, NESB, NASA Langley Research Center, Hampton, VA 23681, Korea Research Institute of Stardards and Science, Daejeon, South Korea, 305-600, Department of Chemical Engineering, Sogang University, South Korea, 121-742, Indiana University, University of Chicago, LBNL, BNL/NSLS, KEK, Fermi National Accelerator Laboratory, LANL, University of Maryland, NIST, HMI, Harvard University, NCSU, Department of Physics and Astronomy, University of Nebraska, University of Southern California, University of California at Los Angeles, Stanford Linear Accelerator Center, Institute for Advanced Physics, Konkuk University, Korea, SUNY College at Oneonta, Department of Physics, University of Wisconsin-Whitewater, Whitewater WI 53190, Cyclotron Institute, Texas A\&M University, College Station, TX, University of Texas at El Paso, University of Buenos Aires, Cyclotron Institute, Texas A\&M University, College Station, TX 77843, Simon Bolivar University, Caracas, Venezuela, Warsaw University, Warsaw, Poland, Institut de Recherches Subatomiques, Strasbourg, France, Florida State University, Harvard-Smithsonian CfA, CENPA University of Washington, Pasadena City College, California State University, Northridge, California State University, Dominguez Hills, Chinese University of Hong Kong, Jet Propulsion Lab, California Institute of Technology, University of California, Irvine, Instituto de F\'isica, UNAM, University of Toronto, Friedrich-Schiller-Universitaet Jena, Pennsylvania State University, NIH, Stanford University, CNR, Italy, University of Texas, Austin, University of Nevada, Reno, University of Wisconsin-Madison, Hanseo University, Division of Materials Science and Technology, KIST, Seoul, 130-791, Korea, Department of Physics, Kangwon National University, Chuncheon, 200-701, Korea, Department of Techno-marketing, Mokwon University, Taejeon, 301-729, Korea, Institute of Physics and Applied Physics, Yonsei University, Seoul, 120-749, Korea, UNAM, Mexico, JINR, Dubna, Univ. of Notre-Dame, ANL, SUNY at Stony Brook, Lund U., ORNL, Washington U., Warsaw, Poland, Saclay, France, Boston University, National Institute for Standards and Technology, Boulder, Los Alamos National Laboratory, Yale University, Florida International University, MIT, Saint Mary's University, TRI-University Meson Facility, Institute of Nuclear Physics, Prague, Czech Republic, Institute of Physics and Nuclear Engineering, Bucharest, Romania, Cyclotron Institute, Texas A\&M Univ., Physics Division, Argonne National Laboratory, Wright Nuclear Structure Laboratory, Yale University, Tenn. Tech. Univ., Arizona State Univ., Ohio Univ., Tennessee Technologival Univ., ORNL Physics Division, Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, University of California, CEA, LLNL, Penn State Altoona, NC A&T State University, TUNL, NASA Langley Research Center, University of Iowa, UMD \& NASA/GSFC, NRC \& NASA/GSFC, NASA/GSFC, Academy at UAH, Oak Ridge National Laboratory, North Carolina State University, Union College, University of Hamburg, Iowa State University, Drake University, Lawrence Livermore National Laboratory, University of Arizona, UNC, Chapel Hill, NC, Tennessee Tech., Cookeville, TN, Rutgers Univ., New Brunswick, NJ, ORNL, Oak Ridge, TN, ORAU, Oak Ridge, TN, Collegium of Natural Sciences, Eckerd College, RIKEN (Institute of Physical and Chemical Research), Department of Physics, Rikkyo University, Department of Physics, University of Tokyo, Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University, Tokyo Inst. of Tech., Rikkyo Univ., Univ. of Tokyo, RIKEN, NSCL, Michigan State University, Dept. of Physics, University of Surrey, Guildford, UK, National Superconducting Cyclotron Laboratory, Michigan State University, University of Surrey, UK, IRES CNRS Strasbourg, Planetary Science Institute, Steward Observatory, University of Oklahoma, Vatican Observatory, University of Rochester, UIUC, Washington State University, Johns Hopkins University, Istituto Nazionale di Fisica Nucleare-Genova
Raffaella De Vita

Kent State University, Jefferson Lab, Ohio University, Mainz University, Mainz, Germany, Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany, University of Washington, Noncommercial Partnership ``Scientific Instruments,'' Moscow, Russia, Lucent Technologies, North-West Technical University, St. Petersburg, Russia, Indiana University-Purdue University Indianapolis, Purdue University, University of Florida, Wabash College and Purdue University, University of Oregon, Garnett McKeen Lab, Inc., Korea Research Institute of Standards and Science, Daejeon, South Korea, 305-600, Department of Physics, Lab. of Solid State Microstructure, Nanjing University, Nanjing, 200008, China, Department of Physics, Hampton University, Hampton, VA 23668, NESB, NASA Langley Research Center, Hampton, VA 23681, Korea Research Institute of Stardards and Science, Daejeon, South Korea, 305-600, Department of Chemical Engineering, Sogang University, South Korea, 121-742, Indiana University, University of Chicago, LBNL, BNL/NSLS, KEK, Fermi National Accelerator Laboratory, LANL, University of Maryland, NIST, HMI, Harvard University, NCSU, Department of Physics and Astronomy, University of Nebraska, University of Southern California, University of California at Los Angeles, Stanford Linear Accelerator Center, Institute for Advanced Physics, Konkuk University, Korea, SUNY College at Oneonta, Department of Physics, University of Wisconsin-Whitewater, Whitewater WI 53190, Cyclotron Institute, Texas A\&M University, College Station, TX, University of Texas at El Paso, University of Buenos Aires, Cyclotron Institute, Texas A\&M University, College Station, TX 77843, Simon Bolivar University, Caracas, Venezuela, Warsaw University, Warsaw, Poland, Institut de Recherches Subatomiques, Strasbourg, France, Florida State University, Harvard-Smithsonian CfA, CENPA University of Washington, Pasadena City College, California State University, Northridge, California State University, Dominguez Hills, Chinese University of Hong Kong, Jet Propulsion Lab, California Institute of Technology, University of California, Irvine, Instituto de F\'isica, UNAM, University of Toronto, Friedrich-Schiller-Universitaet Jena, Pennsylvania State University, NIH, Stanford University, CNR, Italy, University of Texas, Austin, University of Nevada, Reno, University of Wisconsin-Madison, Hanseo University, Division of Materials Science and Technology, KIST, Seoul, 130-791, Korea, Department of Physics, Kangwon National University, Chuncheon, 200-701, Korea, Department of Techno-marketing, Mokwon University, Taejeon, 301-729, Korea, Institute of Physics and Applied Physics, Yonsei University, Seoul, 120-749, Korea, UNAM, Mexico, JINR, Dubna, Univ. of Notre-Dame, ANL, SUNY at Stony Brook, Lund U., ORNL, Washington U., Warsaw, Poland, Saclay, France, Boston University, National Institute for Standards and Technology, Boulder, Los Alamos National Laboratory, Yale University, Florida International University, MIT, Saint Mary's University, TRI-University Meson Facility, Institute of Nuclear Physics, Prague, Czech Republic, Institute of Physics and Nuclear Engineering, Bucharest, Romania, Cyclotron Institute, Texas A\&M Univ., Physics Division, Argonne National Laboratory, Wright Nuclear Structure Laboratory, Yale University, Tenn. Tech. Univ., Arizona State Univ., Ohio Univ., Tennessee Technologival Univ., ORNL Physics Division, Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, University of California, CEA, LLNL, Penn State Altoona, NC A&T State University, TUNL, NASA Langley Research Center, University of Iowa, UMD \& NASA/GSFC, NRC \& NASA/GSFC, NASA/GSFC, Academy at UAH, Oak Ridge National Laboratory, North Carolina State University, Union College, University of Hamburg, Iowa State University, Drake University, Lawrence Livermore National Laboratory, University of Arizona, UNC, Chapel Hill, NC, Tennessee Tech., Cookeville, TN, Rutgers Univ., New Brunswick, NJ, ORNL, Oak Ridge, TN, ORAU, Oak Ridge, TN, Collegium of Natural Sciences, Eckerd College, RIKEN (Institute of Physical and Chemical Research), Department of Physics, Rikkyo University, Department of Physics, University of Tokyo, Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University, Tokyo Inst. of Tech., Rikkyo Univ., Univ. of Tokyo, RIKEN, NSCL, Michigan State University, Dept. of Physics, University of Surrey, Guildford, UK, National Superconducting Cyclotron Laboratory, Michigan State University, University of Surrey, UK, IRES CNRS Strasbourg, Planetary Science Institute, Steward Observatory, University of Oklahoma, Vatican Observatory, University of Rochester, UIUC, Washington State University, Johns Hopkins University, Istituto Nazionale di Fisica Nucleare-Genova
Raffaella De Vita

Kent State University, Jefferson Lab, Ohio University, Mainz University, Mainz, Germany, Max-Planck-Institute for Nuclear Physics, Heidelberg, Germany, University of Washington, Noncommercial Partnership ``Scientific Instruments,'' Moscow, Russia, Lucent Technologies, North-West Technical University, St. Petersburg, Russia, Indiana University-Purdue University Indianapolis, Purdue University, University of Florida, Wabash College and Purdue University, University of Oregon, Garnett McKeen Lab, Inc., Korea Research Institute of Standards and Science, Daejeon, South Korea, 305-600, Department of Physics, Lab. of Solid State Microstructure, Nanjing University, Nanjing, 200008, China, Department of Physics, Hampton University, Hampton, VA 23668, NESB, NASA Langley Research Center, Hampton, VA 23681, Korea Research Institute of Stardards and Science, Daejeon, South Korea, 305-600, Department of Chemical Engineering, Sogang University, South Korea, 121-742, Indiana University, University of Chicago, LBNL, BNL/NSLS, KEK, Fermi National Accelerator Laboratory, LANL, University of Maryland, NIST, HMI, Harvard University, NCSU, Department of Physics and Astronomy, University of Nebraska, University of Southern California, University of California at Los Angeles, Stanford Linear Accelerator Center, Institute for Advanced Physics, Konkuk University, Korea, SUNY College at Oneonta, Department of Physics, University of Wisconsin-Whitewater, Whitewater WI 53190, Cyclotron Institute, Texas A\&M University, College Station, TX, University of Texas at El Paso, University of Buenos Aires, Cyclotron Institute, Texas A\&M University, College Station, TX 77843, Simon Bolivar University, Caracas, Venezuela, Warsaw University, Warsaw, Poland, Institut de Recherches Subatomiques, Strasbourg, France, Florida State University, Harvard-Smithsonian CfA, CENPA University of Washington, Pasadena City College, California State University, Northridge, California State University, Dominguez Hills, Chinese University of Hong Kong, Jet Propulsion Lab, California Institute of Technology, University of California, Irvine, Instituto de F\'isica, UNAM, University of Toronto, Friedrich-Schiller-Universitaet Jena, Pennsylvania State University, NIH, Stanford University, CNR, Italy, University of Texas, Austin, University of Nevada, Reno, University of Wisconsin-Madison, Hanseo University, Division of Materials Science and Technology, KIST, Seoul, 130-791, Korea, Department of Physics, Kangwon National University, Chuncheon, 200-701, Korea, Department of Techno-marketing, Mokwon University, Taejeon, 301-729, Korea, Institute of Physics and Applied Physics, Yonsei University, Seoul, 120-749, Korea, UNAM, Mexico, JINR, Dubna, Univ. of Notre-Dame, ANL, SUNY at Stony Brook, Lund U., ORNL, Washington U., Warsaw, Poland, Saclay, France, Boston University, National Institute for Standards and Technology, Boulder, Los Alamos National Laboratory, Yale University, Florida International University, MIT, Saint Mary's University, TRI-University Meson Facility, Institute of Nuclear Physics, Prague, Czech Republic, Institute of Physics and Nuclear Engineering, Bucharest, Romania, Cyclotron Institute, Texas A\&M Univ., Physics Division, Argonne National Laboratory, Wright Nuclear Structure Laboratory, Yale University, Tenn. Tech. Univ., Arizona State Univ., Ohio Univ., Tennessee Technologival Univ., ORNL Physics Division, Laboratory for High Energy Astrophysics, NASA Goddard Space Flight Center, University of California, CEA, LLNL, Penn State Altoona, NC A&T State University, TUNL, NASA Langley Research Center, University of Iowa, UMD \& NASA/GSFC, NRC \& NASA/GSFC, NASA/GSFC, Academy at UAH, Oak Ridge National Laboratory, North Carolina State University, Union College, University of Hamburg, Iowa State University, Drake University, Lawrence Livermore National Laboratory, University of Arizona, UNC, Chapel Hill, NC, Tennessee Tech., Cookeville, TN, Rutgers Univ., New Brunswick, NJ, ORNL, Oak Ridge, TN, ORAU, Oak Ridge, TN, Collegium of Natural Sciences, Eckerd College, RIKEN (Institute of Physical and Chemical Research), Department of Physics, Rikkyo University, Department of Physics, University of Tokyo, Department of Physics and Astronomy and National Superconducting Cyclotron Laboratory, Michigan State University, Tokyo Inst. of Tech., Rikkyo Univ., Univ. of Tokyo, RIKEN, NSCL, Michigan State University, Dept. of Physics, University of Surrey, Guildford, UK, National Superconducting Cyclotron Laboratory, Michigan State University, University of Surrey, UK, IRES CNRS Strasbourg, Planetary Science Institute, Steward Observatory, University of Oklahoma, Vatican Observatory, University of Rochester, UIUC, Washington State University, Johns Hopkins University, Istituto Nazionale di Fisica Nucleare-Genova