There were 71 new TNO discoveries announced since the previous issue of Distant EKOs:
2013 EM149, 2013 GA138, 2013 GB138, 2013 GC137, 2013 GC138, 2013 GD137, 2013 GD138, 2013 GE137, 2013 GE138, 2013 GF137, 2013 GF138, 2013 GG137, 2013 GG138, 2013 GH137, 2013 GJ137, 2013 GK137, 2013 GL137, 2013 GM137, 2013 GN137, 2013 GO136, 2013 GO137, 2013 GP137, 2013 GQ136, 2013 GQ137, 2013 GR136, 2013 GR137, 2013 GS137, 2013 GT136, 2013 GT137, 2013 GU136, 2013 GU137, 2013 GV136, 2013 GV137, 2013 GW136, 2013 GW137, 2013 GX136, 2013 GX137, 2013 GY137, 2013 GZ137, 2013 HR156, 2013 HS156, 2013 HT156, 2013 JA65, 2013 JB65, 2013 JC65, 2013 JD65, 2013 JE64, 2013 JE65, 2013 JF65, 2013 JG64, 2013 JG65, 2013 JH65, 2013 JJ64, 2013 JJ65, 2013 JK65, 2013 JL65, 2013 JM64, 2013 JM65, 2013 JN65, 2013 JO65, 2013 JP65, 2013 JQ65, 2013 JR65, 2013 JS64, 2013 JS65, 2013 JT64, 2013 JT65, 2013 JU64, 2013 JY64, 2013 JZ64, 2014 VT37
and 19 new Centaur/SDO discoveries:
2013 GA137, 2013 GP136, 2013 GS136, 2013 GY136, 2013 GZ136, 2013 JC64, 2013 JD64, 2013 JF64, 2013 JH64, 2013 JK64, 2013 JL64, 2013 JN64, 2013 JO64, 2013 JP64, 2013 JQ64, 2013 JR64, 2013 JV64, 2014 QR441, 2015 PN291
Reclassified objects:
2002 GG166 (TNOSDO)
2011 UR412 (SDO
2013 GA137 (SDO
Objects recently assigned numbers:
1999 ON4 = (439858)
2010 VZ98 = (445473)
2001 FO185 = (443843)
2004 EU95 = (444018)
2004 HJ79 = (444025)
2004 NT33 = (444030)
2007 JF43 = (444745)
Deleted/Re-identified objects:
2015 KB157 = 2013 LU28
Current number of TNOs: 1445 (including Pluto)
Current number of Centaurs/SDOs: 474
Current number of Neptune Trojans: 12
Out of a total of 1931 objects:
661 have measurements from only one opposition
638 of those have had no measurements for more than a year
329 of those have arcs shorter than 10 days
(for more details, see:
http://www.boulder.swri.edu/ekonews/objects/recov_stats.jpg)
The Pluto system was recently explored by NASA's New Horizons spacecraft, making closest approach on 14 July 2015. Pluto's surface displays diverse landforms, terrain ages, albedos, colors, and composition gradients. Evidence is found for a water-ice crust, geologically young surface units, surface ice convection, wind streaks, volatile transport, and glacial flow. Pluto's atmosphere is highly extended, with trace hydrocarbons, a global haze layer, and a surface pressure near 10 microbars. Pluto's diverse surface geology and long term activity raise fundamental questions about how small planets remain active many billions of years (Gyr) after formation. Pluto's large moon Charon displays tectonics and evidence for a heterogeneous crustal composition; its North Pole displays puzzling dark terrain. Small satellites Hydra and Nix have higher albedos than expected.
Published in: Science, 350, 292 (2015 Oct 16)
Available on the web at http://www.sciencemag.org/content/350/6258/aad1815
Spectroscopic investigation of the surface of Pluto allows us to constrain the chemical properties of the volatile species of the solar system reservoir. This permits us to obtain the relative abundances of various molecules, their physical properties, as well as their spatial and temporal variation. This also could tell us about the origin of various minor chemical compounds formed during the solar system formation or generated later on by space weathering. This will give us critical information about the evolution processes that may occur in the entire trans-Neptunian objects population, and in particular the biggest objects, which could retain tenuous atmospheres.
New observations of the surface of Pluto have been carried out along with reanalyses of older observations carried out with the ESO-VLT telescopes and the SINFONI instrument at a mean spectral resolution of 1500. We present three new near-infrared spectra of Pluto observed at different epochs, and covering the H and K spectral bands showing absorption features of methane, nitrogen, and carbon monoxide ices. We ran different spectral models, based on Hapke theory, to constrain the physical and chemical properties of different sides of Pluto.
We have confirmed the spatial and secular variation of the spectral properties of the surface of Pluto. The abundances, sizes, and temperatures of different ices, such as CH4, CO, and N2 have been constrained for different parts of the surface of Pluto. The results suggest a temperature probably just above the alpha-beta transition phase of N2 (close to 36.5 K), and a probable stratification of the dilution state of CO and CH4. The presence of minor chemical compounds, such as C2H6, has been confirmed too, and for data obtained at several sub-Earth east longitudes. Solid C2H4 is suggested by the spectral modeling with abundance variation following that of solid C2H6 and solid CH4.
Published in: Astronomy & Astrophysics, 582, A39 (2015 October)
For preprints, contact frederic.merlin@obspm.fr
NASA's New Horizons spacecraft flies past Pluto on July 14, 2015,
carrying two instruments that detect charged particles. Pluto has a
tenuous, extended atmosphere that is escaping the planet's weak gravity.
The interaction of the solar wind with Pluto's escaping atmosphere
depends on solar wind conditions as well as the vertical structure of
Pluto's atmosphere. We have analyzed Voyager 2 particles and fields
measurements between 25 and 39 AU and present their statistical
variations. We have adjusted these predictions to allow for the Sun's
declining activity and solar wind output. We summarize the range of SW
conditions that can be expected at 33 AU and survey the range of scales
of interaction that New Horizons might experience. Model estimates for
the solar wind stand-off distance vary from 
7 to 1000 RP with our best
estimate being around 40 RP (where we take Pluto's radius to be RP=1184 km).
To appear in: Journal of Geophysical Research: Planets, v. 120
For preprints, contact bagenal@colorado.edu
and available on the web at http://arxiv.org/abs/1509.04660
The goal of this work is to investigate the composition of the surface of (50000) Quaoar and its spatial variability.
We present new continuous spectra from visible to near-infrared
(0.3-2.3 
m) obtained with the X-Shooter instrument at the VLT-ESO
at four different epochs on the surface of Quaoar. The data, which, for
this object, represent the highest spectral resolution data ever
obtained and the first near-IR dataset acquired in a single exposure
over the entire wavelength range, are complemented by previously
published photometric observations obtained in the near-infrared (3.6,
4.5 m) with the Spitzer Space Telescope, which provide an extra set
of constraints in the model calculation. Spectral modeling was performed
for the entire wavelength range by means of a code based on the
Shkuratov radiative transfer formulation and using an updated value of
albedo obtained from recent Herschel observations.
We obtain compositional information for different observed areas which
can cover about 40% of the assumed rotational period of 8.84 hrs. Our
analysis supports the presence of CH4 and C2H6, as previously
reported, along with indications of possible presence of
NH
H2O. New evidence for the presence of N2 is inferred
from the shift of the CH4 bands. The albedo at the two Spitzer bands
suggests, for one of the surface locations, the possible presence of CO
diluted in N2, and CO2.
The spectral similarities indicate overall homogeneity of the surface
composition of one hemisphere of Quaoar, while some subtle variations
are apparent when modeling is performed. The presence of
NHH2O would support the idea that Quaoar's surface may be
relatively young as previously suggested by Jewitt and Luu (2004).
To appear in: Astronomy & Astrophysics
For preprints, contact antonella.barucci@obspm.fr
Icy dwarf planets are key for studying the chemical and physical states of ices in the outer solar system. The study of secular and rotational variations gives us hints of the processes that contribute to the evolution of their surface. The aim of this work is to search for rotational variability on the surface composition of the dwarf planet (136472) Makemake
We observed Makemake in April 2008 with the medium-resolution
spectrograph ISIS, at the William Herschel Telescope (La Palma, Spain)
and obtained a set of spectra in the 0.28-0.52 m and
0.70-0.95 m ranges, covering 82% of its rotational period. For the
rotational analysis, we organized the spectra in four different sets
corresponding to different rotational phases, and after discarding one
with low signal to noise, we analyzed three of them that cover 71% of
the surface. For these spectra we computed the spectral slope and
compared the observed spectral bands of methane ice with reflectances of
pure methane ice to search for shifts of the center of the bands,
related to the presence of CH4/N2 solid solution.
All the spectra have a red color with spectral slopes between 20%/1000 Å and 32%/1000 Å in accordance with previously reported values. Some variation in the spectral slope is detected, pointing to the possibility of a variation in the surface content or the particle size of the solid organic compound. The absorption bands of methane ice present a shift toward shorter wavelengths, indicating that methane (at least partially) is in solid solution with nitrogen. There is no variation within the errors of the shifts with the wavelength or with the depth of the bands, so there is no evidence of variation in the CH4/N2 mixing ratio with rotation. By comparing with all the available data in the literature, no secular compositional variations between 2005 and 2008 is found.
Published in:
Astronomy 
Astrophysics, 577, A86 (2015 May)
Preprint available on the web at http://arxiv.org/abs/1504.02350
Stellar occultations by asteroids and outer solar system bodies can
offer ground based observers with modest telescopes and camera equipment
the opportunity to probe the shape, size, atmosphere, and attendant
moons or rings of these distant objects. The essential requirements of
the camera and recording equipment are: good quantum efficiency and low
noise; minimal dead time between images; good horological faithfulness
of the image timestamps; robustness of the recording to unexpected
failure; and low cost. We describe an occultation observing and
recording system which attempts to fulfill these requirements and compare
the system with other reported camera and recorder systems. Five systems
have been built, deployed, and tested over the past three years, and we
report on three representative occultation observations: one being a
9
1.5 s occultation of the trans-Neptunian object 28978 Ixion (mv = 15.2)
at 3 seconds per frame; one being a 1.510.017 s occultation of
Deimos, the 12 km diameter satellite of Mars, at 30 frames per second;
and one being a 11.040.4 s occultation, recorded at 7.5 frames per
second, of the main belt asteroid 361 Havnia, representing a low
magnitude drop (
) occultation.
Published in: Publications of the Astronomical Society of Australia, 32, 31
Preprint available the web at http://arxiv.org/abs/1507.05151
In this paper we investigate the opportunities provided by the James Webb Space Telescope (JWST) for significant scientific advances in the study of solar system bodies and rings using stellar occultations. The strengths and weaknesses of the stellar occultation technique are evaluated in light of JWST's unique capabilities. We identify several possible JWST occultation events by minor bodies and rings, and evaluate their potential scientific value. These predictions depend critically on accurate a priori knowledge of the orbit of JWST near the Sun-Earth Lagrange-point 2 (L2). We also explore the possibility of serendipitous stellar occultations by very small minor bodies as a by-product of other JWST observing programs. Finally, to optimize the potential scientific return of stellar occultation observations, we identify several characteristics of JWST's orbit and instrumentation that should be taken into account during JWST's development.
To appear in: Publications of the Astronomical Society of the Pacific
For preprints, contact psantos@iaa.es
Preprint available on the web at http://arxiv.org/abs/1510.06575
m I. Secular and Longitudinal Distribution of Ices and Complex Organics
During the last 30 years the surface of Pluto has been characterized,
and its variability has been monitored, through continuous near-infrared
spectroscopic observations. But in the visible range only few data are
available. The aim of this work is to define the Pluto's relative
reflectance in the visible range to characterize the different
components of its surface, and to provide ground based observations in
support of the New Horizons mission. We observed Pluto on six
nights between May and July 2014, with the imager/spectrograph ACAM at
the William Herschel Telescope (La Palma, Spain). The six
spectra obtained cover a whole rotation of Pluto (Prot = 6.4 days).
For all the spectra we computed the spectral slope and the depth of the
absorption bands of methane ice between 0.62 and 0.90 m. To search
for shifts of the center of the methane bands, associated with dilution
of CH4 in N2, we compared the bands with reflectances of pure
methane ice. All the new spectra show the methane ice absorption bands
between 0.62 and 0.90 m. The computation of the depth of the band
at 0.62 m in the new spectra of Pluto, and in the spectra of
Makemake and Eris from the literature, allowed us to estimate the
Lambert coefficient at this wavelength, at a temperature of 30 K and 40 K,
never measured before. All the detected bands are blue shifted with
respect to the position for pure methane ice, with minimum shifts in
correspondence with the regions where the abundance of methane is
higher. This could be indicative of a dilution of CH4:N2 more
saturated in CH4. The longitudinal and secular variations of the
parameters measured in the spectra are in accordance with results
previously reported in the literature and with the distribution of the
dark and bright material that show the Pluto's albedo maps from
New Horizons.
Submitted to:
Astronomy Astrophysics
Preprint available on the web at http://arxiv.org/abs/1509.00417
Large Kuiper Belt Objects are conventionally thought to have formed out
of a massive planetesimal belt that is a few thousand times its current
mass. Such a picture, however, is incompatible with multiple lines of
evidence. Here, we present a new model for the conglomeration of Cold
Classical Kuiper belt objects, out of a solid belt only a few times its
current mass, or a few percent of the solid density in a Minimum Mass
Solar Nebula. This is made possible by depositing most of the
primordial mass in grains of size centimetre or smaller. These grains
collide frequently and maintain a dynamically cold belt out of which
large bodies grow efficiently: an order-unity fraction of the solid mass
can be converted into large bodies, in contrast to the 
efficiency in conventional models. Such a light belt may represent the
true outer edge of the Solar system, and it may have effectively halted
the outward migration of Neptune. In addition to the high efficiency,
our model can also produce a mass spectrum that peaks at an
intermediate size, similar to the observed Cold Classicals, if one
includes the effect of cratering collisions. In particular, the
observed power-law break observed at 
km for Cold
Classicals, one that has been interpreted as a result of collisional
erosion, may be primordial in origin.
Submitted to: The Astrophysical Journal
For preprints, contact shannon@ast.cam.ac.uk
or on the web at http://arxiv.org/abs/1510.01323
The Group of Orbital Dynamics & Planetology invites applications for post-doc positions. There are 4 positions that will be funded by FAPESP (Fundação de Amparo à Pesquisa do Estado de São Paulo). The candidates must have experience on Planetary Dynamics and/or Spacecraft Dynamics.
The projects to be developed are the following:
* Spin-orbit coupling in solar system dynamics;
* Problems in orbital dynamics involving small bodies under gravitational close approaches;
* Dynamics of narrow planetary rings and small satellites;
* Attitude and orbit analysis for a mission to a triple asteroid system;
The projects will be developed in one of the following institutions: I) São Paulo State University - UNESP in Guaratinguetá; II) National Institute for Space Research - INPE in São José dos Campos. Applicants should send a statement of research interest and a curriculum vitae with a list of publications to: Prof. Othon Winter (email: ocwinter@gmail.com)
We accept submissions for the following sections:
Distant EKOs is not a refereed publication, but is a tool for furthering communication among people interested in Kuiper belt research. Publication or listing of an article in the Newsletter or the web page does not constitute an endorsement of the article's results or imply validity of its contents. When referencing an article, please reference the original source; Distant EKOs is not a substitute for peer-reviewed journals.
