It is with much sadness to report the death of Brian Marsden on November 18, 2010. Most people who get this newsletter are familiar with Brian both personally and through his work at the CBAT/MPC, his work in celestial mechanics, his encouragement and advice to amateur and professional astronomers alike for obtaining high-quality astrometry, and entertaining discussions of mythology and historical astronomy.
http://www.minorplanetcenter.org/mpec/K10/K10W10.html
http://www.cfa.harvard.edu/iau/cbet/002500/CBET002554.txt
There were 8 new TNO discoveries announced since the previous issue of Distant EKOs:
2010 SB41, 2010 TJ, 2010 TR19, 2010 TY53, 2010 VQ11, 2010 VR11, 2010 VS11, 2010 VZ98
and 1 new Centaur/SDO discovery:
2010 WG9
Reclassified objects:
2007 OC10 (SDOTNO)
2010 RO64 (SDO
2010 VR11 (TNO
Current number of TNOs: 1164 (including Pluto)
Current number of Centaurs/SDOs: 289
Current number of Neptune Trojans: 7
Out of a total of 1460 objects:
634 have measurements from only one opposition
577 of those have had no measurements for more than a year
324 of those have arcs shorter than 10 days
(for more details, see:
http://www.boulder.swri.edu/ekonews/objects/recov_stats.jpg)
From time series CCD observations of a fixed and large star field that
contained the binary trans-Neptunian object (90482) Orcus (formerly 2004 DW),
taken during a period of 33 days, we have been able to derive
high-precision relative astrometry and photometry of the Orcus system
with respect to background stars. The right ascension residuals of an
orbital fit to the astrometric data revealed a periodicity of 9.7
0.3 days,
which is what one would expect to be induced by the known
Orcus companion (Vanth). The residuals are also correlated with the
theoretical positions of the satellite with regard to the primary. We
therefore have revealed the presence of Orcus' satellite in our
astrometric measurements, although the residuals in declination did not
show the expected variations. The oscillation in the residuals is caused
by the photocenter motion of the combined Orcus plus satellite system
around the barycenter along an orbital revolution of the satellite. The
photocenter motion is much larger than the motion of Orcus around the
barycenter, and we show here that detecting some binaries through a
carefully devised astrometric technique might be feasible with
telescopes of moderate size. We discuss the prospects for using the
technique to find new binary trans-Neptunian objects (TNOs) and to study
already known binary systems with uncertain orbital periods. We also
analyzed the system's mid-term photometry in order to determine whether
the rotation could be tidally locked to the satellite's orbital period.
We found that a photometric variability of 9.70.3 days is clear
in our data, and is nearly coincident with the orbital period of the
satellite. We believe this variability might be induced by the
satellite's rotation. In our photometry there is also a slight hint for
an additional very small variability in the 10 hr range that was already
reported in the literature. This short-term variability would indicate
that the primary is not tidally locked and therefore the system would
not have reached a double synchronous state. Implications for the basic
physical properties of the primary and its satellite are discussed. From
angular momentum considerations we suspect that the Orcus satellite
might have formed from a rotational fission. This requires that the mass
of the satellite would be around 0.09 times that of the primary, close
to the value that one derives by using an albedo of 0.12 for the
satellite and assuming equal densities for both the primary and
secondary.
Published in: Astronomy and Astrophysics, 525, 31 (2011 January)
For preprints, contact ortiz@iaa.es
or on the web at http://arxiv.org/abs/1010.6187/
Runway growth is an important stage in planet formation during which large
protoplanets form, while most of the initial mass remains in small
planetesimals. The amount of mass converted into large protoplanets and their
resulting size distribution are not well understood. Here, we use analytic
work, that we confirm by coagulation simulations, to describe runaway growth
and the corresponding evolution of the velocity dispersion. We find that
runaway growth proceeds as follows: Initially all the mass resides in small
planetesimals, with mass surface density 
, and large protoplanets
start to form by accreting small planetesimals. This growth continues until
growth by merging large protoplanets becomes comparable to growth by
planetesimal accretion. This condition sets in when
, where 
is the mass surface density in
protoplanets in a given logarithmic mass interval and 
is the ratio of
the size of a body to its Hill radius. From then on, protoplanetary growth and
the evolution of the velocity dispersion become self-similar and
remains roughly constant, since an increase in by accretion of small
planetesimals is balanced by a decrease due to merging with large
protoplanets. We show that this growth leads to a protoplanet size
distribution given by
where N(>R) is the number of
objects with radii greater than R (i.e., a differential power-law index of
4). Since only the largest bodies grow significantly during runaway
growth, and thereby the size distribution is preserved. We apply our
results to the Kuiper Belt, which is a relic of runaway growth where planet
formation never proceeded to completion. Our results successfully match the
observed Kuiper belt size distribution, they illuminate the physical processes
that shaped it and explain the total mass that is present in large Kuiper belt
objects (KBOs) today. This work suggests that the current mass in large KBOs
is primordial and that it has not been significantly depleted. We also predict
a maximum mass-ratio of Kuiper belt binaries that formed by dynamical
processes of
, which explains the observed clustering
in binary companion sizes that is seen in the cold classical belt. Finally,
our results also apply to growth in debris disks, as long as frequent
planetesimal-planetesimal collisions are not important during the growth.
To appear in: The Astrophysical Journal
For preprints, contact hilke@ucla.edu
or on the web at http://arxiv.org/abs/1011.0201
Considering the model of the initial disc of planetesimals consisting of
14799 test particles, we simulated the formation of the populations of
small bodies in the outer region of the solar system for an initial
2 Gyr period. We aimed to provide a common reference model of the
formation of all inner and outer parts of the Oort cloud. In this paper,
we deal with a picture of the trans-Neptunian-belt populations which can
be outlined within our simple model. The dynamical evolution of massless
test particles is followed via numerical integration of their orbits. We
consider perturbations by four giant planets in their current orbits and
with their current masses, as well as perturbations by the Galactic tide
and passing stars. Our simulation qualitatively reproduces almost all
structural features observed in the trans-Neptunian region.
Unfortunately, there are a lot of quantitative discrepancies between our
model and observed reality implying the main conclusion that the
assumption of a dynamically very cold initial proto-planetary disc (with
eccentricity 
0.01 and inclination 0.01 rad), which extends beyond the
heliocentric distance of about 34 AU, is inconsistent with the observed
structure of trans-Neptunian population of small bodies. A big
discrepancy is the survival of an almost untouched initial model
population beyond 34 AU which is not observed. Two following positive
observed details of the TN-population structure can, perhaps, be
explained with the help of our simple model. Concerning the first, we
showed that the outer border of the range of Neptune's perturbation on
the dynamically cold orbits is identical with the outer border of 2:1
mean-motion resonance with this planet, where a sharp decrease of the
number density of bodies belonging to the classical Edgeworth-Kuiper
belt is observed. Most probably, this decrease is related to Neptune's
ability to significantly influence the motion of small bodies, if we
assume that these bodies formed closer to the Sun and were transported
into the belt by Neptune. Second, the outer border of the objects of the
so-called detached subpopulation is approximately at the same
heliocentric distance of 100 AU in both model and observational samples.
For preprints, contact mjakubik@ta3.sk
or on the web at
http://www.ta3.sk/caosp/Eedition/Abstracts/2010/Vol_40/No_2/pp107-129_abstract.html
Following our earlier work studying the formation of the Neptunian
Trojan population during the planet's migration, we present results
examining the eventual fate of the Trojan clouds produced in that work.
A large number of Trojans were followed under the gravitational
influence of the giant planets for a period of at least 1 Gyr. We find
that the stability of Neptunian Trojans seems to be strongly correlated
to their initial post-migration orbital elements, with those objects
that survive as Trojans for billions of years displaying negligible
orbital evolution. The great majority of these survivors began the
integrations with small eccentricities (e < 0.2) and small libration
amplitudes (A < 30 - 40 deg). The survival rate of ``pre-formed''
Neptunian Trojans (which in general survived on dynamically cold orbits
(e < 0.1, i < 5 - 10 deg)) varied between 5 and 70%, depending on the
precise detail of their initial orbits. By contrast, the survival rate
of ``captured'' Trojans (on final orbits spread across a larger region of
e-i element space) were markedly lower, ranging between 1 and 10% after
4 Gyr. Taken in concert with our earlier work and the broad
i-distribution of the observed Trojan population, we note that planetary
formation scenarios which involve the slow migration (a few tens of
millions of years) of Neptune from an initial planetary architecture
that is both resonant and compact (aN < 18 AU) provide the most
promising fit of those we considered to the observed Trojan population.
In such scenarios, we find that the current day Trojan population would
number 1% of that which was present at the end of the planet's
migration (i.e., survival rate of 1%), with the bulk being sourced from
captured, rather than pre-formed objects. We note, however, that even
those scenarios still fail to reproduce the currently observed portion
of the Neptune Trojan population moving on orbits with e < 0.1 but i >
20 deg. Dynamical integrations of the currently observed Trojans show
that five out of the seven are dynamically stable on timescales
comparable to the age of the Solar system, while 2001 QR322, exhibits
significant dynamical instability on timescales of less than 1 Gyr. The
seventh Trojan object, 2008 LC18, was only recently discovered, and has
such large orbital uncertainties that only future studies will be able
to determine its stability.
To appear in: Monthly Notices of the Royal Astronomical Society
For preprints, contact patryksan@gmail.com
or on the web at http://sites.google.com/site/patryksofialykawka/
In a previous paper, we presented a global view of the stability of
Neptune Trojans (NTs hereafter) on inclined orbits. As the
continuation of the investigation, we discuss in this paper the
dependence of the stability of NT orbits on the eccentricity. For
this task, high-resolution dynamical maps are constructed using the
results of extensive numerical integrations of orbits initialized on
fine grids of initial semimajor axis (a0) versus eccentricity
(e0). The extensions of regions of stable orbits on the (a0,
e0) plane at different inclinations are shown. The maximum
eccentricities of stable orbits in the three most stable regions at
low (
), medium (
) and high
(
) inclination are found to be 0.10, 0.12 and
0.04, respectively. The fine structures in the dynamical maps are
described. Via the frequency-analysis method, the mechanisms that
portray the dynamical maps are revealed. The secondary resonances,
at the frequency of the librating resonant angle
and the frequency of the quasi 2:1 mean-motion resonance
(MMR hereafter) between Neptune and Uranus, are found to be deeply
involved in the motion of NTs. Secular resonances are detected and
they also contribute significantly to the triggering of chaos in the
motion. In particular, the effects of the secular resonance
are clarified.
We also investigate the orbital stabilities of six observed NTs by checking the orbits of hundreds of clones generated within the observing error bars. We conclude that four of them are deeply inside the stable region, with 2001 QR322 and 2005 TO74 being the exceptions. 2001 QR322 is in the close vicinity of the most significant secondary resonance. 2005 TO74 is located close to the boundary separating stable orbits from unstable ones, and it may be influenced by a secular resonance.
To appear in: Monthly Notices of the Royal Astronomical Society
For preprints, contact zhouly@nju.edu.cn
or on the web at http://arxiv.org/abs/1007.5362 and
http://onlinelibrary.wiley.com/doi/10.1111/j.1365-2966.2010.17566.x/pdf
The Trojan asteroids, a very substantial population of primitive bodies
trapped in Jupiter’s stable Lagrange regions, remain quite poorly
understood. Because they occupy these orbits, the physical properties
of Trojans provide unique perspective on chemical and dynamical
processes that shaped the Solar System. The current study was therefore
undertaken to investigate surface compositions of these objects. We
present 66 new near-infrared (NIR; 0.7 to 2.5 
m) spectra of 58
Trojan asteroids, including members of both the leading and trailing
swarms. We also include in the analysis previously published NIR
spectra of 13 Trojans (3 of which overlap with the new sample). This
data set permits not only a direct search for compositional signatures,
but also a search for patterns that may reveal clues to the origin of
the Trojans. We do not report any confirmed absorption features in the
new spectra. Analysis of the spectral slopes, however, reveals an
interesting bimodality among the NIR data. The two spectral groups
identified appear to be equally abundant in the leading and trailing
swarms. The spectral groups are not a result of family membership; they
occur in the background, non-family population. The average albedos of
the two groups are the same within uncertainties (0.0510.016 and
0.0550.016). No correlations between spectral slope and any other
physical or orbital parameter are detected, with the exception of a
possible weak correlation with inclination among the less-red spectral
group. The NIR spectral groups are consistent with a similar bimodality
previously suggested among visible colors and spectra. Synthesizing the
present results with previously published properties of Trojans, we
conclude that the two spectral groups represent object with different
intrinsic compositions. We further suggest that while the less-red
group originated near Jupiter or in the main asteroid belt, the redder
spectral group originated farther out in the Solar System. If this
suggestion is correct, the Trojan swarms offer the most readily
accessible large reservoir of Kuiper Belt material as well as a unique
reservoir for the study of material from the middle part of the solar
nebula.
Published in: The Astronomical Journal, 141, 25 (2011 January)
For preprints, contact jemery2@utk.edu
or on the web at http://arxiv.org/abs/1012.1284
The dwarf planet (90377) Sedna is one of the most remote solar system
objects accessible to investigations. To better constrain its surface
composition and to investigate the possible heterogeneity of the surface
of Sedna, several observations have been carried out at ESO-VLT with the
powerful spectrometer SINFONI observing simultaneously the H and K
bands. The analyzed spectra (obtained in 2005, 2007, and 2008) show a
non-uniform spectral signature, particularly in the K band. Spectral
modeling using the Shkuratov radiative transfer code for surface
scattering has been performed using the various sets of data, including
previous observations at visible wavelengths and photometry at 3.6 and
4.5 m by the Spitzer Space Telescope. The visible and near-IR spectra
can be modeled with organic materials (triton and titan tholin),
serpentine, and H2O ice in fairly significant amounts, and CH4, N2 and
C2H6 in varying trace amounts. One of the spectra obtained in October,
2005, shows a different signature in the K-band and is best modeled with
CH3OH in place of CH4, with reduced amounts of serpentine and with the
addition of olivine. The compositional surface heterogeneity can give
input on the past history as well clues to the origin of this peculiar,
distant object.
Published in: The Astronomical Journal, 140, 2095 (2010 December)
For preprints, contact antonella.barucci@obspm.fr
We present spectra of Eris from the MMT 6.5 meter telescope and Red
Channel Spectrograph (5700-9800 Å; 5 Å pix-1) on Mt.
Hopkins, AZ, and of Pluto from the Steward Observatory 2.3 meter
telescope and Boller and Chivens spectrograph (7100-9400 Å; 2 Å pix-1)
on Kitt Peak, AZ. In addition, we present laboratory
transmission spectra of methane-nitrogen and methane-argon ice mixtures.
By anchoring our analysis in methane and nitrogen solubilities in one
another as expressed in the phase diagram of Prokhvatilov & Yantsevich
(1983), and comparing methane bands in our Eris and Pluto spectra and
methane bands in our laboratory spectra of methane and nitrogen ice
mixtures, we find Eris' bulk methane and nitrogen abundances are
10% and 90% and Pluto's bulk methane and nitrogen abundances
are 3% and 97%. Such abundances for Pluto are
consistent with values reported in the literature. It appears that the
bulk volatile composition of Eris is similar to the bulk volatile
composition of Pluto. Both objects appear to be dominated by nitrogen
ice. Our analysis also suggests, unlike previous work reported in the
literature, that the methane and nitrogen stoichiometry is constant with
depth into the surface of Eris. Finally, we point out that our Eris
spectrum is also consistent with a laboratory ice mixture consisting of
40% methane and 60% argon. Although we cannot rule out an argon rich
surface, it seems more likely that nitrogen is the dominant species on
Eris because the nitrogen ice 2.15 m band is seen in spectra of
Pluto and Triton.
Published in: The Astrophysical Journal, 725, 1296-1305 (2010 December 10)
For preprints, contact Stephen.Tegler@nau.edu
or on the web at http://arxiv.org/abs/1010.4821
We present new photometric and spectroscopic observations of the
Pluto–Charon system carried out at the VLT-ESO (Chile) with two 8-m
telescopes equipped with the FORS2, ISAAC and SINFONI instruments. The
spectra were obtained in the 0.6-2.45 m range with a spectral
resolution from 300 to 1500. The SINFONI data were obtained using
adaptive optics, allowing a complete separation of the two bodies. We
derive both objects' magnitudes in the near infrared and convert them
into albedo values. These first near infrared photometric data allow to
adjust the different parts of Pluto's spectrum, provided by the three
instruments. We run spectral models in order to give chemical and
physical constraints on the surface of Pluto and Charon. We discuss the
dilution properties of the methane ice and its implications on Pluto's
surface. The heterogeneities of the pure and diluted methane ice on
Pluto's surface is also investigated. The high signal-to-noise level of
the data and our analyses may support the presence of ethane ice on the
surface of Pluto, which is one of the main products of the methane
irradiation and photolysis. The analyses of the spectra of Charon
suggest that the water ice is almost completely in its crystalline form
and that the ammonia compound is hydrated on the surface of this
satellite.
Published in: Icarus, 210, 930 (2010 December)
Physical Properties of Trans-Neptunian Binaries (120347) 2004 SB60 and (42355) Typhon-Echidna
J.A. Stansberry1, W.M. Grundy2, M. Mueller3, S.D. Benecchi4, G.H. Rieke1, K.S. Noll5, M.W. Buie6, H.F. Levison6, S.B. Porter2, and H.G. Roe2
1 Steward Observatory, University of Arizona, Tucson AZ, USA
2 Lowell Observatory, Flagstaff AZ, USA
3 Observatoire de la Cóte d'Azur, Nice, France
4 Planetary Science Institute, Tucson AZ, USA
5 Space Telescope Science Institute, Baltimore MD, USA
6 Southwest Research Institute, Boulder CO, USA
Submitted to: Icarus
For preprints, contact stansber@as.arizona.edu
On the Existence of Distant Solar Companion and Its Possible Effects on the Oort Cloud and the Observed Comet Population
Julio A. Fernández1
1 Departamento de Astronomía, Facultad de Ciencias, Iguá 4225, 11400 Montevideo, Uruguay
The Astrophysical Journal
For preprints, contact Julio A. Fernández julio@fisica.edu.uy
Microwave Emission from the Edgeworth-Kuiper Belt and the Asteroid Belt Constrained from WMAP
Kazuhide Ichikawa1 and Masataka Fukugita1,2,3
1 Institute for Cosmic Ray Research, University of Tokyo, Kashiwa 277-8582, Japan
2 Institute for Advanced Study, Princeton, NJ 08540, USA
3 Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwa 277-8583, Japan
Preprints on the web at
http://arxiv.org/abs/1011.4796
The characteristics of the populations of objects that inhabit the outer solar system carry the fingerprint of the processes that governed the formation and evolution of the solar system. Occultation surveys push the limit of observation into the very small and distant outer solar system objects, allowing us to set constraints on the structure of the Kuiper belt, Scattered disk and Sedna populations. I collected, reduced, and analyzed vast datasets looking for occultations of stars by outer solar system objects, both working with the Taiwanese American Occultation Survey (TAOS) collaboration and leading the MMT/Megacam occultation effort. Having found no such events in my data, I was able to place upper limits on the Kuiper belt, scattered disk and Sedna population. These limits and their derivation are described here.
Dissertation directed by C. R. Alcock
Ph.D. awarded on March 2010 from the University of Pennsylvania
For copies, contact fbianco@lcogt.net
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.