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We present Keplerian orbit solutions for the mutual orbits of 17 transneptunian binary systems (TNBs). For ten of them, the orbit had not previously been known: 60458 2000 CM 114 , 119979 2002 WC 19 , 160091 2000 OL 67 , 160256 2002 PD 149 , 469514 2003 QA 91 , 469705 ǂKá̦gára, 508788 2000 CQ 114 , 508869 2002 VT 130 , 1999 RT 214 , and 2002 XH 91 . Seven more are systems where the size, shape, and...
We present high spatial resolution images of the binary transneptunian object Gǃkúnǁ'hòmdímà (229762 2007 UK 126 ) obtained with the Hubble Space Telescope and with the Keck observatory on Mauna Kea to determine the orbit of Gǃò'é ǃhúGǃò'é ǃhú, the much smaller and redder satellite. Gǃò'é ǃhú orbits in a prograde sense, on a circular or near-circular orbit with a period of 11.3 days and a semimajor...
Pluto's atmospheric haze settles out rapidly compared with geological timescales. It needs to be accounted for as a surface material, distinct from Pluto's icy bedrock and from the volatile ices that migrate via sublimation and condensation on seasonal timescales. This paper explores how a steady supply of atmospheric haze might affect three distinct provinces on Pluto. We pose the question of why...
Charon, the largest moon of Pluto, appeared as a fairly homogeneous, gray, icy world to New Horizons during closest approach on July 14th, 2015. Charon's sub-Pluto hemisphere was scanned by the Ralph/LEISA near-IR spectrograph providing an unprecedented opportunity to measure its surface composition. We apply a statistical clustering tool to identify spectrally distinct terrains and a radiative transfer...
We discuss two semi-independent calibration techniques used to determine the inflight radiometric calibration for the New Horizons’ Multi-spectral Visible Imaging Camera (MVIC). The first calibration technique compares the measured number of counts (DN) observed from a number of well calibrated stars to those predicted using the component-level calibration. The ratio of these values provides a multiplicative...
On July 14th 2015, NASA’s New Horizons mission gave us an unprecedented detailed view of the Pluto system. The complex compositional diversity of Pluto’s encounter hemisphere was revealed by the Ralph/LEISA infrared spectrometer on board of New Horizons. We present compositional maps of Pluto defining the spatial distribution of the abundance and textural properties of the volatiles methane and nitrogen...
Light curves produced from color observations taken during New Horizons’ approach to the Pluto-system by its Multi-spectral Visible Imaging Camera (MVIC, part of the Ralph instrument) are analyzed. Fifty seven observations were analyzed, they were obtained between 9th April and 3rd July 2015, at a phase angle of 14.5° to 15.1°, sub-observer latitude of 51.2 °N to 51.5 °N, and a sub-solar latitude...
From Earth based observations Pluto is known to be the host of N2, CH4 and CO ices and also a dark red material. Very limited spatial distribution information is available from rotational visible and near-infrared spectral curves obtained from hemispheric measurements. In July 2015 the New Horizons spacecraft reached Pluto and its satellite system and recorded a large set of data. The LEISA spectro-imager...
New Horizon's accurate determination of the sizes and densities of Pluto and Charon now permit precise internal models of both bodies to be constructed. Assuming differentiated rock-ice structures, we find that Pluto is close to 2/3 solar-composition anhydrous rock by mass and Charon 3/5 solar-composition anhydrous rock by mass. Pluto and Charon are closer to each other in density than to other large...
In this work we investigated the longitudinal (zonal) variability of H2O and ammonia (NH3) hydrate ices on the surface of Charon through analysis of the 1.65 µm and 2.21 µmabsorption features, respectively. Near-infrared spectra presented here were obtained between 2015-07-14 and 2015-08-30 UT with the OSIRIS integral field spectrograph on Keck I. Spectra centered on six different sub-observer longitudes...
We present the results of an investigation to determine the longitudinal (zonal) distributions and temporal evolution of ices on the surface of Triton. Between 2002 and 2014, we obtained 63 nights of near-infrared (0.67–2.55μm) spectra using the SpeX instrument at NASA’s Infrared Telescope Facility (IRTF). Triton has spectral features in this wavelength region from N2, CO, CH4, CO2, and H2O. Absorption...
From observations by the Hubble Space Telescope, Keck II Telescope, and Gemini North Telescope, we have determined the mutual orbit of the large transneptunian object (174567) Varda and its satellite Ilmarë. These two objects orbit one another in a highly inclined, circular or near-circular orbit with a period of 5.75days and a semimajor axis of 4810km. This orbit reveals the system mass to be (2...
The methane–nitrogen phase diagram of Prokhvatilov and Yantsevich (1983. Sov. J. Low Temp. Phys. 9, 94–98) indicates that at temperatures relevant to the surfaces of icy dwarf planets like Pluto, two phases contribute to the methane absorptions: nitrogen saturated with methane N2‾:CH4 and methane saturated with nitrogen CH4‾:N2. No optical constants are available so far for the latter component limiting...
The surface of Pluto as it is understood on the eve of the encounter of the New Horizons spacecraft (mid-2015) consists of a spatially heterogeneous mix of solid N2, CH4, CO, C2H6, and an additional component that imparts color, and may not be an ice. The known molecular ices are detected by near-infrared spectroscopy. The N2 ice occurs in the hexagonal crystalline β-phase, stable at T>35.6K. Spectroscopic...
We present the results of an investigation using near-infrared spectra of Pluto taken on 72 separate nights using SpeX/IRTF. These data were obtained between 2001 and 2013 at various sub-observer longitudes. The aim of this work was to confirm the presence of ethane ice and to determine any longitudinal trends on the surface of Pluto. We computed models of the continuum near the 2.405μm band using...
A new Hubble Space Telescope observation of the 7:4 resonant transneptunian binary system (385446) Manwë has shown that, of two previously reported solutions for the orbit of its satellite Thorondor, the prograde one is correct. The orbit has a period of 110.18±0.02days, semimajor axis of 6670±40km, and an eccentricity of 0.563±0.007. It will be viewable edge-on from the inner Solar System during...
A superior mutual event of the Kuiper Belt binary system (79360) Sila–Nunam was observed over 15.47h on UT 7/8 February 2013 by a coordinated effort at four different telescope facilities; it started ∼1.5h earlier than anticipated, the duration was ∼9.5h (about 10% longer than predicted), and was slightly less deep than predicted. It is the first full event observed for a comparably sized binary Kuiper...
We report results from monitoring Pluto’s 0.8 to 2.4μm reflectance spectrum with IRTF/SpeX on 65 nights over the dozen years from 2001 to 2012. The spectra show vibrational absorption features of simple molecules CH 4 , CO, and N 2 condensed as ices on Pluto’s surface. These absorptions are modulated by the planet’s 6.39day rotation period, enabling us to constrain the longitudinal...
Hubble Space Telescope observations between 2001 and 2010 resolved the binary components of the Cold Classical transneptunian object (79360) Sila–Nunam (provisionally designated 1997 CS 29 ). From these observations we have determined the circular, retrograde mutual orbit of Nunam relative to Sila with a period of 12.50995±0.00036days and a semimajor axis of 2777±19km. A multi-year season...
In an initial laboratory exploration of the CH 4 +N 2 system we demonstrate that under equilibrium conditions ice will float when the molar percentage abundance of N 2 in the liquid is ⩾∼15.
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