81 research outputs found
The Mutual Orbit, Mass, and Density of Transneptunian Binary Gknhmdm (229762 2007 UK126)
We present high spatial resolution images of the binary transneptunian object Gkn'hmdm (229762 2007 UK126) obtained with the Hubble Space Telescope and with the Keck observatory on Mauna Kea to determine the orbit of G' hG' h, the much smaller and redder satellite. G' h orbits in a prograde sense, on a circular or near-circular orbit with a period of 11.3 days and a semimajor axis of 6000 km. Tidal evolution is expected to be slow, so it is likely that the system formed already in a low-eccentricity configuration, and possibly also with the orbit plane of the satellite in or close to the plane of Gkn'hmdm's equator. From the orbital parameters we can compute the system mass to be 1.4 10(exp 20) kg. Combined with estimates of the size of Gkn'hmdm from thermal observations and stellar occultations, we can estimate the bulk density as about 1 g cm(exp 3). This low density is indicative of an ice-rich composition, unless there is substantial internal porosity. We consider the hypothesis that the composition is not unusually ice-rich compared with larger TNOs and comet nuclei, and instead the porosity is high, suggesting that mid-sized objects in the 400 to 1000 km diameter range mark the transition between small, porous objects and larger objects that have collapsed their internal void space as a result of their much higher internal pressures and temperatures
De-biased Populations of Kuiper Belt Objects from the Deep Ecliptic Survey
The Deep Ecliptic Survey (DES) discovered hundreds of Kuiper Belt objects
from 1998-2005. Follow-up observations yielded 304 objects with good dynamical
classifications (Classical, Scattered, Centaur, or 16 mean-motion resonances
with Neptune). The DES search fields are well documented, enabling us to
calculate the probability of detecting objects with particular orbital
parameters and absolute magnitudes at a randomized point in each orbit.
Grouping objects together by dynamical class leads, we estimate the orbital
element distributions (a, e, i) for the largest three classes (Classical, 3:2,
and Scattered) using maximum likelihood. Using H-magnitude as a proxy for the
object size, we fit a power law to the number of objects for 8 classes with at
least 5 detected members (246 objects). The best Classical slope is
alpha=1.02+/-0.01 (observed from 5<=H<=7.2). Six dynamical classes (Scattered
plus 5 resonances) are consistent in slope with the Classicals, though the
absolute number of objects is scaled. The exception to the power law relation
are the Centaurs (non-resonant with perihelia closer than Neptune, and thus
detectable at smaller sizes), with alpha=0.42+/-0.02 (7.5<H<11). This is
consistent with a knee in the H-distribution around H=7.2 as reported elsewhere
(Bernstein et al. 2004, Fraser et al. 2014). Based on the Classical-derived
magnitude distribution, the total number of objects (H<=7) in each class are:
Classical (2100+/-300 objects), Scattered (2800+/-400), 3:2 (570+/-80), 2:1
(400+/-50), 5:2 (270+/-40), 7:4 (69+/-9), 5:3 (60+/-8). The independent
estimate for the number of Centaurs in the same H range is 13+/-5. If instead
all objects are divided by inclination into "Hot" and "Cold" populations,
following Fraser et al. (2014), we find that alphaHot=0.90+/-0.02, while
alphaCold=1.32+/-0.02, in good agreement with that work.Comment: 26 pages emulateapj, 6 figures, 5 tables, accepted by A
Buoyancy waves in Pluto's high atmosphere: Implications for stellar occultations
We apply scintillation theory to stellar signal fluctuations in the
high-resolution, high signal/noise, dual-wavelength data from the MMT
observation of the 2007 March 18 occultation of P445.3 by Pluto. A well-defined
high wavenumber cutoff in the fluctuations is consistent with viscous-thermal
dissipation of buoyancy waves (internal gravity waves) in Pluto's high
atmosphere, and provides strong evidence that the underlying density
fluctuations are governed by the gravity-wave dispersion relation.Comment: Accepted 18 June 2009 for publication in Icaru
The Orbit of Transneptunian Binary Manw\"e and Thorondor and their Upcoming Mutual Events
A new Hubble Space Telescope observation of the 7:4 resonant transneptunian
binary system (385446) Manw\"e 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 0.02 days, semimajor axis of
6670 40 km, and an eccentricity of 0.563 0.007. It will be viewable
edge-on from the inner solar system during 2015-2017, presenting opportunities
to observe mutual occultation and eclipse events. However, the number of
observable events will be small, owing to the long orbital period and expected
small sizes of the bodies relative to their separation. This paper presents
predictions for events observable from Earth-based telescopes and discusses the
associated uncertainties and challenges.Comment: 15 pages, 3 figures, 5 table
The UT 7/8 February 2013 Sila-Nunam Mutual Event and Future Predictions
A superior mutual event of the Kuiper Belt binary system (79360) Sila-Nunam was observed over 15.47 h on UT 7/8 February 2013 by a coordinated effort at four different telescope facilities; it started approximately 1.5 h earlier than anticipated, the duration was approximately 9.5 h (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 Belt object. We provide predictions for future events refined by this and other partial mutual event observations obtained since the mutual event season began
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