There were no new TNO discoveries announced since the previous issue of Distant EKOs, but there was 1 new Centaur/SDO discovery:
2012 QQ14
and 1 new Neptune Trojan discovery:
2011 HM102
Reclassified objects:
2010 RF43 (SDOTNO)
Objects recently assigned numbers:
2010 NV1 = (336756)
Current number of TNOs: 1252 (including Pluto)
Current number of Centaurs/SDOs: 356
Current number of Neptune Trojans: 9
Out of a total of 1617 objects:
642 have measurements from only one opposition
626 of those have had no measurements for more than a year
320 of those have arcs shorter than 10 days
(for more details, see:
http://www.boulder.swri.edu/ekonews/objects/recov_stats.jpg)
We describe the instrumentation and detection software and characterize
the detection efficiency of an automated, all-sky, southern-hemisphere
search for Kuiper Belt objects brighter than R mag 21.4. The search
relies on Yale University's 160-Megapixel QUEST camera, previously used
for successful surveys at Palomar that detected most of the distant
dwarf planets, and now installed on the ESO 1.0-m Schmidt telescope at
La Silla, Chile. Extensive upgrades were made to the telescope control
system to support automation, and significant improvements were made to
the camera. To date, 63 new KBOs have been discovered, including a new
member of the Haumea collision family (2009 YE7) and a new distant
object with inclination exceeding 70 deg (2010 WG9). In a survey
covering 
7500 deg2, we have thus far detected 77 KBOs and Centaurs,
more than any other full-hemisphere search to date. Using a pattern of
dithered pointings, we demonstrate a search efficiency exceeding 80%. We
are currently on track to complete the southern-sky survey and detect
any bright KBOs that have eluded detection from the north.
To appear in: The Astronomical Journal
Preprints available on the web at http://arxiv.org/abs/1205.5214
) Collisional Family
The Haumea family is currently the only identified collisional family in
the Kuiper belt. We numerically simulate the long-term dynamical
evolution of the family to estimate a lower limit of the family's age
and to assess how the population of the family and its dynamical
clustering are preserved over Gyr timescales. We find that the family is
not younger than 100 Myr, and its age is at least 1 Gyr with 95%
confidence. We find that for initial velocity dispersions of 50-400 m/s,
approximately 20-45% of the family members are lost to
close encounters with Neptune after 3.5 Gyr of orbital evolution. We
apply these loss rates to two proposed models for the formation of the
Haumea family, a graze-and-merge type collision between two similarly
sized, differentiated KBOs or the collisional disruption of a satellite
orbiting Haumea. For the graze-and-merge collision model, we calculate
that >85% of the expected mass in surviving family members within
150 m/s of the collision has been identified, but that one to
two times the mass of the known family members remains to be identified
at larger velocities. For the satellite-break-up model, we estimate
that the currently identified family members account for 50% of
the expected mass of the family. Taking observational incompleteness
into account, the observed number of Haumea family members is consistent
with either formation scenario at the 
level, however both
models predict more objects at larger relative velocities
(>150 m/s) than have been identified.
Published in: Icarus, 221, 106 (2012 September)
For preprints, contact kvolk@lpl.arizona.edu
: a Large Temporary Quasi-satellite of Neptune
Context. Upon discovery, asteroid (309239) 2007 RW10 was considered a Neptune Trojan candidate. The object is currently listed by the Minor Planet Center as a Centaur but it is classified as a scattered disk or trans-Neptunian object by others. Now that its arc-length is 8154 d and has been observed for more than 20 yr, a more robust classification should be possible.
Aims. Here we explore the orbital behaviour of this object in order to reveal its current dynamical status.
Methods. We perform N-body simulations in both directions of time to investigate the evolution of its orbital elements. In particular, we study the librational properties of the mean longitude.
Results. Its mean longitude currently librates around the
value of the mean longitude of Neptune with an amplitude of nearly 50
and a period of about 7.5 kyr. Our calculations show that it has been in
its present dynamical state for about 12.5 kyr and it will stay there
for another 12.5 kyr. Therefore, its current state is relatively
short-lived. Due to its chaotic behaviour, the object may have remained
in the 1:1 mean motion resonance with Neptune for several 100 kyr at
most, undergoing transitions between the various resonant states.
Conclusions. (309239) 2007 RW10 is currently a
quasi-satellite, the first object of this dynamical class to be
discovered around Neptune. With a diameter of about 250 km, it is the
largest known co-orbital in the solar system. Although it is not a
Centaur now, it may become one in the future as it appears to move in an
unstable region. Its significant eccentricity (0.30) and inclination
(36), strongly suggest that it did not form in situ but was captured,
likely from beyond Neptune. With an apparent magnitude of 21.1 at
opposition (October), it is well suited for spectroscopic observations
that may provide information on its composition and hence eventually its
origin.
Published in: Astronomy and Astrophysics, 545, L9 (2012 September)
For preprints, contact nbplanet@fis.ucm.es
or on the web at http://adsabs.harvard.edu/abs/2012A%26A...545L...9D
The optical colors of 58 objects in mean motion resonance with Neptune
were obtained. The various Neptune resonant populations were found to
have significantly different surface color distributions. The 5:3 and
7:4 resonances have semi-major axes near the middle of the main Kuiper
Belt and both are dominated by ultra-red material (spectral gradient:
). The 5:3 and 7:4 resonances have statistically the
same color distribution as the low inclination ``cold'' classical
belt. The inner 4:3 and distant 5:2 resonances have objects with
mostly moderately red colors (
), similar to the scattered
and detached disk populations. The 2:1 resonance, which is near the
outer edge of the main Kuiper Belt, has a large range of colors with
similar numbers of moderately red and ultra-red objects at all
inclinations. The 2:1 resonance was also found to have a very rare
neutral colored object showing that the 2:1 resonance is really a mix
of all object types. The inner 3:2 resonance, like the outer 2:1, has
a large range of objects from neutral to ultra-red. The Neptune
Trojans (1:1 resonance) are only slightly red (
), similar to
the Jupiter Trojans. The inner 5:4 resonance only has four objects
with measured colors but shows equal numbers of ultra-red and
moderately red objects. The 9:5, 12:5, 7:3, 3:1 and 11:3 resonances
do not have reliable color distribution statistics since few objects
have been observed in these resonances, though it appears noteworthy
that all three of the measured 3:1 objects have only moderately red
colors, similar to the 4:3 and 5:2 resonances. The different color
distributions of objects in mean motion resonance with Neptune are
likely a result from the disruption of the primordial Kuiper Belt from
the scattering and migration of the giant planets. The few low
inclination objects known in the outer 2:1 and 5:2 resonances are
mostly only moderately red. This suggests if the 2:1 and 5:2 have a
cold low inclination component, the objects likely had a significantly
different origin than the ultra-red dominated cold components of the
cold classical belt and 5:3 and 7:4 resonances.
To appear in: The Astronomical Journal
For preprints, contact sheppard@dtm.ciw.edu
or on the web at http://arxiv.org/abs/1210.0537
Context. We study the surface properties of transneptunian
populations of solar system bodies.
Aims. We investigate the surface characteristics of the dwarf planet (136472) Makemake and the resonant object (90482) Orcus.
Methods. Using the FORS2 instrument of the ESO-VLT, we carried out linear polarisation measurements of Makemake and Orcus.
Results. Polarisation of Orcus is similar to that of smaller-sized objects. The polarimetric properties of Makemake are very close to those of Eris and Pluto. We did not find any significant differences in the polarisation properties of transneptunian objects (TNOs) from different dynamical classes. However, there are significant differences in the polarisation of the large objects and the smaller ones and between large TNOs with water-ice and methane-ice dominated surfaces.
Conclusions. We confirm the different types of polarisation phase behaviour for the largest and smaller-sized TNOs. To explain subtle surface polarisation of Pluto, Makemake and Eris, we assume that their surfaces are covered by a thin layer of hoarfrost masking the surface structure.
To appear in: Astronomy and Astrophysics
For preprints, contact irina@astron.kharkov.ua
or on the web at http://arxiv.org/abs/1209.6025
Impact ejecta and collisional debris from the Edgeworth-Kuiper Belt are
the dominant source of micron-sized grains in the outer solar system, as
they slowly migrate inwards through the outer solar system before most
grains are ejected during close encounters with Jupiter. These grains
drive several phenomena in the outer solar system, including the
generation of impact ejecta clouds at airless bodies, the formation of
ionospheric layers and neutral gases in the atmospheres of the giant
planets due to meteoric ablation, the generation of tenuous outer
planetary ring systems and the spatial and compositional alteration of
Saturn's main rings. Previous analyses have offered estimates of the net
mass production rate from the Edgeworth-Kuiper Belt both theoretically
and observationally. In order to improve upon these estimates, we
compare measurements of the interplanetary dust density in the outer
solar system by both the Pioneer 10 meteoroid detector and the New
Horizons Student Dust Counter with a dynamical dust grain tracing model.
Our best estimates for the net mass production rate and the ejecta mass
distribution power law exponent are
g/s and
, respectively.
Published in: Geophysical Research Letters, 38, L24102 (2011 December)
For preprints, contact poppe@ssl.berkeley.edu
Dust grains originating from the Edgeworth-Kuiper Belt (EKB) are believed to be the dominant species of dust in the outer solar system. These grains, evolving inward from the EKB under the influence of a variety of forces, will encounter the giant planets or their ring and moon systems. At Saturn, this influx drives several physical processes including the generation of tenuous dusty exospheres and rings, the spatial and compositional evolution of Saturn's main planetary ring system, and the generation of ionospheric and neutral gas layers in the atmospheres of Saturn and Titan. Recent comparisons between in-situ dust density measurements in the outer solar system and a dynamical dust grain tracing model have placed experimental limits on the mass production rate and power-law exponent of EKB-generated grains. Using this model and the experimental constraints, we make predictions for the influx of micron-sized, EKB-generated grains into the saturnian system, where the Cosmic Dust Analyzer onboard the Cassini mission is currently making measurements of both endogenous and exogenous dust populations.
Published in: Geophysical Research Letters, 39, L15104 (2012 August)
For preprints, contact poppe@ssl.berkeley.edu
Spectral analyses of trans-Neptunan objects (TNOs) and of the linked
Centaurs, which are supposed to be among the most primitive minor bodies
in the solar system, reveal some chemical and physical properties of
their surface. To determine the surface composition of these objects and
their surface evolution is essential for gaining clues on the conditions
under which the solar system has been formed. Chemical composition and
physical properties of the surface of three objects have been
constrained by computing the depth of the absorption features of the
spectra in the near-infrared, running spectral models based on radiative
transfer theory in the [0.4-2.3] 
m range, and analyzing new
laboratory measurements of the spectral behavior of thin samples of
H2O-CH3OH mixtures. Our investigations allow us to confirm the
presence of CH3OH ice on the surface of the Centaur (5145) Pholus
and the resonant TNO (55638) 2002 VE95. It
may also possibly be found on the classical TNO (120348) 2004 TY364.
Our laboratory experiments indicate that the behavior of
the methanol and water ice absorption bands is dependent on the ambient
temperature and the dilution level of the mixture. These results also
suggest that methanol may be diluted in water ice on the surface of the
Centaur Pholus. Formation and destruction processes of methanol suggest
that a part (at least) of the surface of these objects is younger than
the solar system age. If confirmed, this shows that primordial ices
could still be detected on the surface of objects that are submitted to
irradiation and rejuvenation processes.
Published in: Astronomy & Astrophysics, 544, 20
For preprints, contact frederic.merlin@obspm.fr
-CH
-CO Mixtures as a Case Study
The space weathering of icy Kuiper Belt Objects was investigated in this case study by exposing methane (CH4) and carbon monoxide (CO) doped nitrogen (N2) ices at 10 K to ionizing radiation in the form of energetic electrons. Online and in situ Fourier transform infrared spectroscopy was utilized to monitor the radiation-induced chemical processing of these ices. Along with isocyanic acid (HNCO), the products could be mainly derived from those formed in irradiated binary ices of the N2-CH4 and CO-CH4 systems: nitrogen-bearing products were found in the form of hydrogen cyanide (HCN), hydrogen isocyanide (HNC), diazomethane (CH2N2), and its radical fragment (HCN2); oxygen-bearing products were of acetaldehyde (CH3CHO), formyl radical (HCO), and formaldehyde (H2CO). As in the pure ices, the methyl radical (CH3) and ethane (C2H6) were also detected, as were carbon dioxide (CO2) and the azide radical (N3). Based on the temporal evolution of the newly formed products, kinetic reaction schemes were then developed to fit the temporal profiles of the newly formed species, resulting in numerical sets of rate constants. The current study highlights important constraints on the preferential formation of isocyanic acid (HNCO) over hydrogen cyanide (HCN) and hydrogen isocyanide (HNC), thus guiding the astrobiological and chemical evolution of those distant bodies.
Published in: The Astrophysical Journal, 758, 37 (2012 October 10)
For preprints, contact ralfk@hawaii.edu
Centaurs are believed to be Kuiper Belt Objects in transition between
Jupiter and Neptune, before possibly becoming Jupiter Family Comets.
Some indirect observational evidence is consistent with the presence of
amorphous water ice in Centaurs. Some of them also display a cometary
activity, probably triggered by the crystallization of the amorphous
water ice, as suggested by Jewitt (2009) and this work. Indeed, we
investigate the survival of amorphous water ice against crystallization,
using a fully 3D thermal evolution model. Simulations are performed for
varying heliocentric distances and obliquities. They suggest that
crystallization can be triggered as far as 16 AU, though amorphous ice
can survive beyond 10 AU. The phase transition is an efficient source of
outgassing up to 10-12 AU, which is broadly consistent with the
observations of the active Centaurs. The most extreme case is
167P/CINEOS which barely crystallizes in our simulations. However,
amorphous ice can be preserved inside Centaurs in many heliocentric
distance-obliquity combinations, below a 5-10 m crystallized
crust. We also find that outgassing due to crystallization cannot be
sustained for a time longer than 104-5 years, leading to the
hypothesis that active Centaurs might have recently suffered from
orbital changes. This could be supported by both observations (although
limited) and dynamical studies.
Published in: The Astronomical Journal, 144, 97 (2012 October)
For preprints, contact aguilber@rssd.esa.int
A number of authors have argued that the Sun must have been born in a
cluster of no more than several thousand stars, on the basis that, in a
larger cluster, close encounters between the Sun and other stars would
have truncated the outer solar system or excited the outer planets into
eccentric orbits. However, this dynamical limit is in tension with
meteoritic evidence that the solar system was exposed to a nearby
supernova during or shortly after its formation; a several-thousand-star
cluster is much too small to produce a massive star whose lifetime is
short enough to have provided the enrichment. In this paper, we revisit
the dynamical limit in the light of improved observations of the
properties of young clusters. We use a series of scattering simulations
to measure the velocity-dependent cross-section for disruption of the
outer solar system by stellar encounters, and use this cross-section to
compute the probability of a disruptive encounter as a function of birth
cluster properties. We find that, contrary to prior work, the
probability of disruption is small regardless of the cluster mass, and
that it actually decreases rather than increases with cluster mass. Our
results differ from prior work for three main reasons: (1) unlike in
most previous work, we compute a velocity-dependent cross-section and
properly integrate over the cluster mass-dependent velocity distribution
of incoming stars; (2) we recognize that 90% of clusters have
lifetimes of a few crossing times, rather than the 10-100 Myr adopted in
many earlier models; and (3) following recent observations, we adopt a
mass-independent surface density for embedded clusters, rather than a
mass-independent radius as assumed many earlier papers. Our results
remove the tension between the dynamical limit and the meteoritic
evidence, and suggest that the Sun was born in a massive cluster. A
corollary to this result is that close encounters in the Sun's birth
cluster are highly unlikely to truncate the Kuiper Belt unless the Sun
was born in one of the unusual clusters that survived for tens of Myr.
However, we find that encounters could plausibly produce highly
eccentric Kuiper Belt objects such as Sedna.
Published in: The Astrophysical Journal, 754, 54 (2012 July 20)
For preprints, contact krumholz@ucolick.org
or on the web at http://www.ucolick.org/~krumholz/publications.html
A 3D General Circulation Model for Pluto and Triton with Fixed Volatile Abundance and Simplified Surface Forcing
A.M. Zalucha1 and T.I. Michaels1
1 SETI Institute, 189 Bernardo Ave., Suite 100, Mountain View, CA, 94043, USA
Submitted to: Icarus
For preprints, contact Angela Zalucha angela@boulder.swri.edu
This workshop in Lund focuses on ice(s) and planet formation. Astrophysical ice has become an increasingly popular topic in the past years, inspired and driven by new observations of ices in molecular clouds and protoplanetary discs, models of dust coagulation and planet formation where ice plays an important role and current and upcoming laboratory experiments on ice collisions and ice deposition.
The goal of the workshop is to bring together observers, experimentalists and theorists to discuss the present state-of-the-art of the field as well as future directions. The workshop will consist of contributed talks and posters, with ample time for discussion during extended breaks and poster sessions.
The Ice and Planet Formation workshop will be held 15 - 17 May 2013 at Lund Observatory in Lund in Sweden. The workshop will start after lunch on Wednesday 15 May and end after lunch on Friday 17 May.
Scientific organising committee:
Jürgen Blum (University of Braunschweig)
Ewine van Dishoeck (Leiden University)
Carsten Dominik (Amsterdam University)
Cornelis Dullemond (Heidelberg University)
Thomas Henning (Max Planck Institute for Astronomy)
Michiel Hogerheijde (Leiden University)
Anders Johansen (Lund University)
Klaus Pontoppidan (Space Telescope Science Institute)
Local organising committee:
Anders Johansen (Lund University)
Katrin Ros (Lund University)
Michiel Lambrechts (Lund University)
Website: http://www.astro.lu.se/~anders/IPF2013/
Registration closes on 15 February 2013.
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.
