29 research outputs found
Asteroid taxonomic signatures from photometric phase curves
We explore the correlation between an asteroid's taxonomy and photometric
phase curve using the H, G12 photometric phase function, with the shape of the
phase function described by the single parameter G12. We explore the usability
of G12 in taxonomic classification for individual objects, asteroid families,
and dynamical groups. We conclude that the mean values of G12 for the
considered taxonomic complexes are statistically different, and also discuss
the overall shape of the G12 distribution for each taxonomic complex. Based on
the values of G12 for about half a million asteroids, we compute the
probabilities of C, S, and X complex membership for each asteroid. For an
individual asteroid, these probabilities are rather evenly distributed over all
of the complexes, thus preventing meaningful classification. We then present
and discuss the G12 distributions for asteroid families, and predict the
taxonomic complex preponderance for asteroid families given the distribution of
G12 in each family. For certain asteroid families, the probabilistic prediction
of taxonomic complex preponderance can clearly be made. The Nysa-Polana family
shows two distinct regions in the proper element space with different G12
values dominating in each region. We conclude that the G12-based probabilistic
distribution of taxonomic complexes through the main belt agrees with the
general view of C complex asteroid proportion increasing towards the outer
belt. We conclude that the G12 photometric parameter cannot be used in
determining taxonomic complex for individual asteroids, but it can be utilized
in the statistical treatment of asteroid families and different regions of the
main asteroid belt.Comment: submitted to Icaru
Force-Extension Relations for Polymers with Sliding Links
Topological entanglements in polymers are mimicked by sliding rings
(slip-links) which enforce pair contacts between monomers. We study the
force-extension curve for linear polymers in which slip-links create additional
loops of variable size. For a single loop in a phantom chain, we obtain exact
expressions for the average end-to-end separation: The linear response to a
small force is related to the properties of the unstressed chain, while for a
large force the polymer backbone can be treated as a sequence of Pincus--de
Gennes blobs, the constraint effecting only a single blob. Generalizing this
picture, scaling arguments are used to include self-avoiding effects.Comment: 4 pages, 5 figures; accepted to Phys. Rev. E (Brief Report
Mutual Events in the Cold Classical Transneptunian Binary System Sila and Nunam
Hubble Space Telescope observations between 2001 and 2010 resolved the binary
components of the Cold Classical transneptunian object (79360) Sila-Nunam
(provisionally designated 1997 CS29). From these observations we have
determined the circular, retrograde mutual orbit of Nunam relative to Sila with
a period of 12.50995 \pm 0.00036 days and a semimajor axis of 2777 \pm 19 km. A
multi-year season of mutual events, in which the two near-equal brightness
bodies alternate in passing in front of one another as seen from Earth, is in
progress right now, and on 2011 Feb. 1 UT, one such event was observed from two
different telescopes. The mutual event season offers a rich opportunity to
learn much more about this barely-resolvable binary system, potentially
including component sizes, colors, shapes, and albedo patterns. The low
eccentricity of the orbit and a photometric lightcurve that appears to coincide
with the orbital period are consistent with a system that is tidally locked and
synchronized, like the Pluto-Charon system. The orbital period and semimajor
axis imply a system mass of (10.84 \pm 0.22) \times 10^18 kg, which can be
combined with a size estimate based on Spitzer and Herschel thermal infrared
observations to infer an average bulk density of 0.72 +0.37 -0.23 g cm^-3,
comparable to the very low bulk densities estimated for small transneptunian
binaries of other dynamical classes.Comment: In press in Icaru
The geology and geophysics of Kuiper Belt object (486958) Arrokoth
The Cold Classical Kuiper Belt, a class of small bodies in undisturbed orbits beyond Neptune, are primitive objects preserving information about Solar System formation. The New Horizons spacecraft flew past one of these objects, the 36 km long contact binary (486958) Arrokoth (2014 MU69), in January 2019. Images from the flyby show that Arrokoth has no detectable rings, and no satellites (larger than 180 meters diameter) within a radius of 8000 km, and has a lightly-cratered smooth surface with complex geological features, unlike those on previously visited Solar System bodies. The density of impact craters indicates the surface dates from the formation of the Solar System. The two lobes of the contact binary have closely aligned poles and equators, constraining their accretion mechanism
Evidence that Pluto's atmosphere does not collapse from occultations including the 2013 May 04 event
© 2014 The Authors. Combining stellar occultation observations probing Pluto's atmosphere from 1988 to 2013, and models of energy balance between Pluto's surface and atmosphere, we find the preferred models are consistent with Pluto retaining a collisional atmosphere throughout its 248-year orbit. The occultation results show an increasing atmospheric pressure with time in the current epoch, a trend present only in models with a high thermal inertia and a permanent N2 ice cap at Pluto's north rotational pole.This work was supported in part by NASA Planetary Astronomy Grant NNX12AG25G.Peer Reviewe
NEOWISE observations of NEOs: preliminary results
VizieR online Data Catalogue associated with article published in journal Astronomical Journal (AAS) with title \u27NEOWISE observations of near-earth objects: preliminary results.\u27 (bibcode: 2011ApJ...743..156M