There were 96 new TNO discoveries announced since the previous issue of
Distant EKOs :
2013 PS76,
2013 SA101,
2013 SB101,
2013 SC101,
2013 SD101,
2013 SE101,
2013 SF101,
2013 SG101,
2013 SJ100,
2013 SL100,
2013 SM100,
2013 SN100,
2013 SO100,
2013 SP100,
2013 SQ100,
2013 SR100,
2013 SS100,
2013 ST100,
2013 SU100,
2013 SV100,
2013 SW100,
2013 SX100,
2013 SY100,
2013 SZ100,
2013 UA17,
2013 UA18,
2013 UB18,
2013 UC18,
2013 UD18,
2013 UE17,
2013 UE18,
2013 UF17,
2013 UF18,
2013 UG17,
2013 UG18,
2013 UH17,
2013 UJ17,
2013 UK17,
2013 UL17,
2013 UM17,
2013 UN17,
2013 UP17,
2013 UQ17,
2013 UR17,
2013 US17,
2013 UT17,
2013 UV17,
2013 UW16,
2013 UW17,
2013 UX16,
2013 UX17,
2013 UY16,
2013 UY17,
2013 UZ16,
2013 UZ17,
2014 UB229,
2014 UB230,
2014 UC228,
2014 UC229,
2014 UC230,
2014 UD229,
2014 UE229,
2014 UF228,
2014 UF229,
2014 UH228,
2014 UH229,
2014 UJ228,
2014 UJ229,
2014 UK229,
2014 UL228,
2014 UL229,
2014 UM228,
2014 UM229,
2014 UN228,
2014 UN229,
2014 UO228,
2014 UO229,
2014 UP228,
2014 UP229,
2014 UQ228,
2014 UR228,
2014 UR229,
2014 US228,
2014 UT228,
2014 UT229,
2014 UU228,
2014 UU229,
2014 UV228,
2014 UW228,
2014 UW229,
2014 UX228,
2014 UX229,
2014 UY228,
2014 UY229,
2014 UZ228,
2014 UZ229
and 19 new Centaur/SDO discoveries:
2013 SK100,
2013 UB17,
2013 UC17,
2013 UD17,
2013 UO17,
2013 UU17,
2014 UA229,
2014 UA230,
2014 UB228,
2014 UD228,
2014 UE228,
2014 UG228,
2014 UG229,
2014 UK228,
2014 UQ229,
2014 US229,
2014 UV229,
2017 UX51,
2017 WW14
Objects recently assigned numbers:
1998 HQ151 = (503858)
2000 YB2 = (506439)
2001 QF331 = (503883)
2003 HB57 = (506479)
2008 SO266 = (504555)
2010 RE188 = (504847)
2013 QO95 = (505412)
2013 SA100 = (505448)
2013 SP99 = (505446)
2013 SQ99 = (505447)
2013 UL15 = (505476)
2013 UM15 = (505477)
2013 UT15 = (505478)
2014 GU53 = (505624)
2014 WT69 = (505679)
2015 HO171 = (506028)
2015 SO20 = (508338)
2016 BP81 = (506121)
Current number of TNOs: 1910 (including Pluto)
Current number of Centaurs/SDOs: 740
Current number of Neptune Trojans: 17
Out of a total of 2667 objects:
704 have measurements from only one opposition
696 of those have had no measurements for more than a year
342 of those have arcs shorter than 10 days
(for more details, see:
http://www.boulder.swri.edu/ekonews/objects/recov_stats.jpg )
PAPERS ACCEPTED TO JOURNALS |
|
Water and Volatiles in the Outer Solar System
O. Grasset1, J. Castillo-Rogez2, T. Guillot3,
L.N. Fletcher4, and F. Tosi5
1 Laboratoire de Planétologie et Géodynamique, LPG-Nantes UMR 6112, France
2 Jet Propulsion Laboratory, California Institute of Technology, USA
3 Observatoire de la Côte d'Azur, France
4 Department of Physics and Astronomy, University of Leicester, UK
5 INAF-IAPS Istituto di Astrofisica e Planetologia Spaziali, Italy
Space exploration and ground-based observations have provided
outstanding evidence of the diversity and the complexity of the outer
solar system. This work presents our current understanding of the nature
and distribution of water and water-rich materials from the water snow
line to the Kuiper Belt. This synthesis is timely, since a thorough
exploration of at least one object in each region of the outer solar
system has now been achieved. Next steps, starting with the Juno mission
now in orbit around Jupiter, will be more focused on understanding the
processes at work than on describing the general characteristics of each
giant planet systems.
Published in:
Space Science Reviews, 212, 835 (2017 October)
Available on the web at http://adsabs.harvard.edu/abs/2017SSRv..212..835G
Checking the Compatibility of the Cold Kuiper Belt with a Planetary Instability Migration Model
Rodney Gomes1, David Nesvorny2, Alessandro Morbidelli3, Rogerio Deienno4 and Erica Nogueira5
1 Observatório Nacional, Rua General José Cristino 77, CEP 20921-400, Rio de Janeiro, RJ, Brazil
2 Department of Space Studies, Southwest Research Institute, 1050 Walnut Street, Boulder, CO 80302, USA
3 Laboratoire Lagrange, UMR7293, Université Côte d'Azur, CNRS, Observatoire de la Côte d'Azur, Boulevard de l'Observatoire, 06304 Nice Cedex 4, France
4 Instituto Nacional de Pesquisas Espaciais, Avenida dos Astronautas 1758, CEP 12227-010 São José dos Campos, SP, Brazil
5 Universidade Federal Fluminense, Niteroi, RJ, Brazil
The origin of the orbital structure of the cold component of the Kuiper
belt is still a hot subject of investigation. Several features of the
solar system suggest that the giant planets underwent a phase of global
dynamical instability, but the actual dynamical evolution of the planets
during the instability is still debated. To explain the structure of the
cold Kuiper belt, Nesvorny (2015, AJ 150,68) argued for a "soft"
instability, during which Neptune never achieved a very eccentric orbit.
Here we investigate the possibility of a more violent instability, from
an initially more compact fully resonant configuration of 5 giant
planets. We show that the orbital structure of the cold Kuiper belt can
be reproduced quite well provided that the cold population formed in
situ, with an outer edge between 44-45 au and never had a large mass.
To appear in:
Icarus
For preprints, contact rodney@on.br
or on the web at https://arxiv.org/abs/1710.05178
A Possible Dynamically Cold Classical Contact Binary:
(126719) 2002 CC249
Audrey Thirouin1 and Scott S. Sheppard2
1 Lowell Observatory, 1400 W Mars Hill Rd, Flagstaff, Arizona, 86001, USA
2 Department of Terrestrial Magnetism, Carnegie Institution for Science, 5241 Broad Branch Rd. NW, Washington, DC, 20015, USA
Images of the Kuiper Belt object (126719) 2002 CC
249 obtained in
2016 and 2017 using the 6.5 m Magellan-Baade Telescope and the 4.3 m
Discovery Channel Telescope are presented. A light curve with a
periodicity of 11.87±0.01 hr and a peak-to-peak amplitude of
0.79±0.04 mag is reported. This high amplitude double-peaked light
curve can be due to a single elongated body, but it is best explained by
a contact binary system from its U-/V-shaped light curve. We present a
simple full-width-at-half-maximum test that can be used to determine if
an object is likely a contact binary or an elongated object based on its
light curve. Considering that 2002 CC
249 is in hydrostatic
equilibrium, a system with a mass ratio q
min = 0.6, and a density
ρ
min = 1 g cm
−3, or less plausible a system with
q
max = 1, and ρ
max = 5 g cm
−3 can interpret the
light curve. Assuming a single Jacobi ellipsoid in hydrostatic
equilibrium and an equatorial view, we estimate ρ ≥ 0.34 g cm
−3,
and a/b = 2.07. Finally, we report a new color study showing
that 2002 CC
249 displays an ultra red surface characteristic of a
dynamically Cold Classical trans-Neptunian object.
Published in:
The Astronomical Journal, 154, 241 (2017 December)
For preprints, contact thirouin@lowell.edu
or on the web at http://adsabs.harvard.edu/abs/2017AJ....154..241T
The Curiously Warped Mean Plane of the Kuiper Belt
K. Volk1 and R. Malhotra1
1 Lunar and Planetary Laboratory, The University of Arizona, 1629 E. University Blvd., Tucson, AZ 85721, USA
We measured the mean plane of the Kuiper belt as a function of
semi-major axis. For the classical Kuiper belt as a whole (the
non-resonant objects in the semi-major axis range 42-48 au), we find a
mean plane of inclination
i
m = 1.8
°+0.7°−0.4° and longitude of
ascending node Ω
m = 77
°+18°−14° (in
the J2000 ecliptic-equinox coordinate system), in accord with
theoretical expectations of the secular effects of the known planets.
With finer semi-major axis bins, we detect a statistically significant
warp in the mean plane near semi-major axes 40-42 au. Linear secular
theory predicts a warp near this location due to the ν
18 nodal
secular resonance, however the measured mean plane for the 40.3-42 au
semi-major axis bin (just outside the ν
18) is inclined
∼ 13
° to the predicted plane, a nearly 3-σ
discrepancy. For the more distant Kuiper belt objects of semi-major axes
in the range 50-80 au, the expected mean plane is close to the
invariable plane of the solar system, but the measured mean plane
deviates greatly from this: it has inclination
i
m = 9.1
°+6.6°−3.8° and longitude of
ascending node Ω
m = 227
°+18°−44°. We
estimate this deviation from the expected mean plane to be statistically
significant at the ∼ 97−99% confidence level. We discuss several
possible explanations for this deviation, including the possibility that
a relatively close-in (a <~100 au), unseen small planetary-mass
object in the outer solar system is responsible for the warping.
Published in:
The Astronomical Journal, 154, 62 (2017 August)
For preprints, contact kvolk@lpl.arizona.edu
or on the web at http://adsabs.harvard.edu/abs/2017AJ....154...62V
Dynamical Evolution Induced by Planet Nine
Konstantin Batygin1 and Alessandro Morbidelli2
1 Division of Geological and Planetary Sciences, California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA
2 Laboratoire Lagrange, Université Côte d'Azur, Observatoire de la Côte d'Azur, CNRS, CS 34229, 06304 Nice, France
The observational census of trans-Neptunian objects with semi-major axes
greater than ∼ 250 AU exhibits unexpected orbital structure that is
most readily attributed to gravitational perturbations induced by a
yet-undetected, massive planet. Although the capacity of this planet to
(i) reproduce the observed clustering of distant orbits in physical
space, (ii) facilitate dynamical detachment of their perihelia from
Neptune, and (iii) excite a population of long-period centaurs to
extreme inclinations is well established through numerical experiments,
a coherent theoretical description of the dynamical mechanisms
responsible for these effects remains elusive. In this work, we
characterize the dynamical processes at play, from semi-analytic
grounds. We begin by considering a purely secular model of orbital
evolution induced by Planet Nine, and show that it is at odds with the
ensuing stability of distant objects. Instead, the long-term survival of
the clustered population of long-period KBOs is enabled by a web of
mean-motion resonances driven by Planet Nine. Then, by taking a
compact-form approach to perturbation theory, we show that it is the
secular dynamics embedded within these resonances that regulates the
orbital confinement and perihelion detachment of distant Kuiper belt
objects. Finally, we demonstrate that the onset of large-amplitude
oscillations of orbital inclinations is accomplished through capture of
low-inclination objects into a high-order secular resonance and identify
the specific harmonic that drives the evolution. In light of the
developed qualitative understanding of the governing dynamics, we offer
an updated interpretation of the current observational dataset within
the broader theoretical framework of the Planet Nine hypothesis.
Published in:
The Astronomical Journal, 154, 229 (2017 December)
For preprints, contact kbatygin@gps.caltech.edu
or on the web at http://adsabs.harvard.edu/abs/2017AJ....154..229B
Dynamically Correlated Minor Bodies in the Outer Solar System
C. de la Fuente Marcos1 and R. de la Fuente Marcos1
1 Universidad Complutense de Madrid, Ciudad Universitaria, E-28040 Madrid, Spain
The organization of the orbits of most minor bodies in the Solar system
seems to follow random patterns, the result of billions of years of
chaotic dynamical evolution. Much as heterogeneous orbital behaviour is
ubiquitous, dynamically coherent pairs and groups of objects are also
present everywhere. Although first studied among the populations of
asteroids and comets that inhabit or traverse the inner Solar system,
where they are very numerous, at least one asteroid family has been
confirmed to exist in the outer Solar system and two other candidates
have been proposed in the literature. Here, we perform a systematic
search for statistically significant pairs and groups of dynamically
correlated objects through those with semimajor axis greater than 25 au,
applying a novel technique that uses the angular separations of orbital
poles and perihelia together with the differences in time of perihelion
passage to single out pairs of relevant objects. Our analysis recovers
well-known, dynamically coherent pairs and groups of comets and
trans-Neptunian objects and uncovers a number of new ones, prime
candidates for further spectroscopic study.
Published in:
Monthly Notices of the Royal Astronomical Society, 474, 838 (2018 Feb)
For preprints, contact nbplanet@ucm.es
or on the web at http://adsabs.harvard.edu/abs/2018MNRAS.474..838D
The Dynamical History of 2060 Chiron and Its Proposed Ring System
Jeremy Wood1,2, Jonti Horner2,3, Tobias C. Hinse4, and Stephen C. Marsden2
1 Hazard Community and Technical College, 1 Community College Drive Hazard, KY 41701, USA
2 University of Southern Queensland, Computational Engineering and Science Research Centre, West St, Toowoomba, QLD 4350, Australia
3 Australian Centre for Astrobiology, UNSW Australia, Sydney, NSW 2052, Australia
4 Korea Astronomy and Space Science Institute, 776 Daedukdae-ro, Yuseong-gu, Daejeon 305-348, Republic of Korea
The surprising discovery of a ring system around the Centaur 10199 Chariklo
in 2013 led to a reanalysis of archival stellar occultation
data for the Centaur 2060 Chiron by Ortiz et al. One possible
interpretation of that data is that a system of rings exists around
Chiron. In this work, we study the dynamical history of the proposed
Chiron ring system by integrating nearly 36,000 clones of the Centaur
backward in time for 100 Myr under the influence of the Sun and the four
giant planets. The severity of all close encounters between the clones
and planets while the clones are in the Centaur region is recorded,
along with the mean time between close encounters. We find that severe
and extreme close encounters are very rare, making it possible that the
Chiron ring system has remained intact since its injection into the
Centaur region, which we find likely occurred within the past 8.5 Myr.
Our simulations yield a backward dynamical half-life for Chiron of 0.7 Myr.
The dynamical classes of a sample of clones are found. It is found
that, on average, the Centaur lifetimes of resonance hopping clones are
twice those of random-walk clones because of resonance sticking in mean
motion resonances. In addition, we present MEGNO and chaotic lifetime
maps of the region bound by 13 au ≤ a ≤ 14 au and
e ≤ 0.5. We confirm that the current mean orbital parameters of
Chiron are located in a highly chaotic region of a-e phase space.
Published in:
The Astronomical Journal, 155, 2 (2018 January)
Available on the web at http://adsabs.harvard.edu/abs/2018AJ....155....2W
Searching for Moving Objects in HSC-SSP: Pipeline and Preliminary Results
Y.-T. Chen1, H.-W. Lin2,3, M. Alexandersen1, M. Lehner1,4,5,
S.-Y. Wang1, J.-H. Wang1, F. Yoshida6,7, Y. Komiyama8, and S. Miyazaki8,9
1 Institute of Astronomy and Astrophysics, Academia Sinica, P. O. Box 23-141, Taipei 106, Taiwan
2 Institute of Astronomy, National Central University, 32001, Taiwan
3 Department of Physics, University of Michigan, Ann Arbor, MI 48109, USA
4 Department of Physics and Astronomy, University of Pennsylvania, 209 S. 33rd St., Philadelphia, PA 19125,
USA
5 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., Cambridge, MA 02138, USA
6 Planetary Exploration Research Center, Chiba Institute of Technology, 2-17-1 Tsudanuma, Narashino, Chiba 275-0016, Japan
7 Department of Planetology, Graduate School of Science, Kobe University, Kobe, 657-8501, Japan
8 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
9 The Graduate University for Advanced Studies), Mitaka, Tokyo, 181-8588, Japan
The Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) is currently
the deepest wide-field survey in progress. The 8.2 m aperture of the
Subaru telescope is very powerful in detecting faint/small moving
objects, including near-Earth objects, asteroids, centaurs and
Tran-Neptunian objects (TNOs). However, the cadence and dithering
pattern of the HSC-SSP are not designed for detecting moving objects,
making it difficult to do so systematically. In this paper, we introduce
a new pipeline for detecting moving objects (specifically TNOs) in a
non-dedicated survey. The HSC-SSP catalogs are sliced into HEALPix
partitions. Then, the stationary detections and false positives are
removed with a machine learning algorithm to produce a list of moving
object candidates. An orbit linking algorithm and visual inspections are
executed to generate the final list of detected TNOs. The preliminary
results of a search for TNOs using this new pipeline on data from the
first HSC-SSP data release (Mar 2014 to Nov 2015) present
231 TNO/Centaurs candidates. The bright candidates with H
r < 7.7
and i > 5 show that the best fit slope of a single power law to
absolute magnitude distribution is 0.77. The g−r color distribution of
hot HSC-SSP TNOs indicates a bluer peak at g−r = 0.9 which is
consistent with the bluer peak of the bimodal color distribution in
literature.
To appear in:
Publications of the Astronomical Society of Japan, HSC special issue
Preprints available on the web at https://arxiv.org/abs/1705.01722
Pipeline for the Detection of Serendipitous Stellar Occultations by Kuiper Belt Objects with the Colibri Fast-photometry Array
E. Pass1,2,3, S. Metchev1,3,4, P. Brown1,3, and S. Beauchemin5
1 Department of Physics and Astronomy, University of Western Ontario, London ON, Canada
2 Department of Physics and Astronomy, University of Waterloo, Waterloo ON, Canada
3 Centre for Planetary Science and Exploration, University of Western Ontario, London ON, Canada
4 Department of Physics and Astronomy, Stony Brook University, Stony Brook NY, USA
5 Department of Computer Science, University of Western Ontario, London ON, Canada
We report results from the preliminary trials of Colibri, a dedicated
fast-photometry array for the detection of small Kuiper belt objects
through serendipitous stellar occultations. Colibri's novel data
processing pipeline analyzed 4000 star hours with two overlapping-field
EMCCD cameras, detecting no Kuiper belt objects and one false positive
occultation event in a high ecliptic latitude field. No occultations
would be expected at these latitudes, allowing these results to provide
a control sample for the upcoming main Colibri campaign. The empirical
false positive rate found by the processing pipeline is consistent with
the 0.002% simulation-determined false positive rate. We also describe
Colibri's software design, kernel sets for modeling stellar
occultations, and method for retrieving occultation parameters from
noisy diffraction curves. Colibri's main campaign will begin in
mid-2018, operating at a 40 Hz sampling rate.
Published in:
Publications of the Astronomical Society of the Pacific, 130, 014502
(2018 January)
For preprints, contact ekpass@edu.uwaterloo.ca
or on the web at https://arxiv.org/abs/1711.00358
Equilibrium Shapes of Large Trans-Neptunian Objects
N. Rambaux1, D. Baguet2,
F. Chambat3, and J.C. Castillo-Rogez4
1 IMCCE, Observatoire de Paris PSL Research University, Sorbonne Universités UPMC Université Paris 06, Université Lille 1, CNRS UMR8028, 77 avenue Denfert-Rochereau, F-75014 Paris, France
2 Institut UTINAM UMR6213, CNRS, Univ. Bourgogne Franche-Comté, OSU Theta F-25000 Besançon, France
3 LGLTPE, CNRS UMR5276, ENS de Lyon, Site Monod, 15 parvis René Descartes; Lyon, F-69007, France
4 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, 91109 CA, USA
The large trans-Neptunian objects (TNO) with radii larger than 400 km
are thought to be in hydrostatic equilibrium. Their shapes can provide
clues regarding their internal structures that would reveal information
on their formation and evolution. In this paper, we explore the
equilibrium figures of five TNOs, and we show that the difference
between the equilibrium figures of homogeneous and heterogeneous
interior models can reach several kilometers for fast rotating and low
density bodies. Such a difference could be measurable by ground-based
techniques. This demonstrates the importance of developing the shape up
to second and third order when modeling the shapes of large and rapid
rotators.
Published in:
The Astrophysical Journal Letters, 850, L9 (2017 November 20)
For reprints, contact Nicolas.Rambaux@obspm.fr
or available on the web at http://adsabs.harvard.edu/abs/2017ApJ...850L...9R
Relevance of Tidal Heating on Large TNOs
P. Saxena1, J. Renaud2, W. Henning1,3, M. Jutzi4, and T. Hurford1
1 NASA/Goddard Space Flight Center, 8800 Greenbelt Rd, Greenbelt, MD 20771, USA
2 Department of Physics & Astronomy, George Mason University, 4400 University Drive, Fairfax, VA 22030, USA
3 Department of Astronomy, University of Maryland, Physical Sciences Complex, College Park, MD 20742 USA
4 Physics Institute: Space Research & Planetary Sciences, University of Bern, Sidlerstrasse 5, Bern 3012, Switzerland
We examine the relevance of tidal heating for large Trans-Neptunian
Objects, with a focus on its potential to melt and maintain layers of
subsurface liquid water. Depending on their past orbital evolution,
tidal heating may be an important part of the heat budget for a number
of discovered and hypothetical TNO systems and may enable formation of,
and increased access to, subsurface liquid water. Tidal heating induced
by the process of despinning is found to be particularly able to compete
with heating due to radionuclide decay in a number of different
scenarios. In cases where radiogenic heating alone may establish
subsurface conditions for liquid water, we focus on the extent by which
tidal activity lifts the depth of such conditions closer to the surface.
While it is common for strong tidal heating and long lived tides to be
mutually exclusive, we find this is not always the case, and highlight
when these two traits occur together. We find cases where TNO systems
experience tidal heating that is a significant proportion of, or greater
than radiogenic heating for periods ranging from 100's of millions to a
billion years. For subsurface oceans that contain a small antifreeze
component, tidal heating due to very high initial spin states may enable
liquid water to be preserved right up to the present day. Of particular
interest is the Eris-Dysnomia system, which in those cases may exhibit
extant cryovolcanism.
Published in:
Icarus, 302, 245 (2018 March 1)
For preprints, contact prabal.saxena@nasa.gov
or on the web at http://adsabs.harvard.edu/abs/2018Icar..302..245S
Photometric Observations of Nine Transneptunian Objects and Centaurs
T. Hromakina1, D. Perna2,3, I. Belskaya1, E. Dotto2, A. Rossi4, and F. Bisi2,5
1 Institute of Astronomy, Kharkiv V.N. Karazin National University, Sumska Str. 35, Kharkiv 61022, Ukraine
2 INAF - Osservatorio Astronomico di Roma, Via Frascati 33, I-00078 Monte Porzio Catone (Roma), Italy
3 LESIA - Observatoire de Paris, PSL Research University, CNRS, Sorbonne Universités, UPMC Univ. Paris 06, Univ. Paris Diderot, Sorbonne Paris Cité, 5 place Jules Janssen, 92195 Meudon, France
4 IFAC-CNR, via Madonna del Piano 10, I-50019 Sesto Fiorentino (Firenze), Italy
5 Dipartimento di Fisica, Università di Roma Tor Vergata, via della Ricerca Scientifica 1, 00133 Roma, Italy
We present the results of photometric observations of six Transneptunian objects
and three Centaurs, estimations of their rotational periods and corresponding
amplitudes. For six of them we present also lower limits of density values. All
observations were made using 3.6-m TNG telescope (La Palma, Spain). For four
objects - (148975) 2001 XA255, (281371) 2008 FC76, (315898) 2008 QD4, and 2008 CT190
- the estimation of short-term variability was made for the first time.
We confirm rotation period values for two objects: (55636) 2002 TX300 and
(202421) 2005 UQ513, and improve the precision of previously reported
rotational period values for other three - (120178) 2003 OP32, (145452) 2005 RN43,
(444030) 2004 NT33 - by using both our and literature data. We also discuss
here that small distant bodies, similarly to asteroids in the Main belt, tend
to have double-peaked rotational periods caused by the elongated shape rather
than surface albedo variations.
Published in:
Monthly Notices of the Royal Astronomical Society, 474, 2536 (2018 Feb)
For preprints, contact hromakina@astron.kharkov.ua
or on the web at https://arxiv.org/abs/1712.04284
Haze Heats Pluto's Atmosphere yet Explains its Cold Temperature
Xi Zhang1, Darrell F. Strobel2, and Hiroshi Imanaka3,4
1 Department of Earth and Planetary Sciences, University of California Santa Cruz, Santa Cruz, CA 95064, USA
2 Department of Earth & Planetary Sciences and Physics & Astronomy, Johns Hopkins University, Baltimore, MD 21218, USA
3 SETI Institute, 189 North Bernardo Avenue, Suite 100, Mountain View, CA 94043, USA
4 NASA Ames Research Center, Moffett Field, CA 94035, USA
Pluto's atmosphere is cold and hazy. Recent observations have shown it
to be much colder than predicted theoretically, suggesting an unknown
cooling mechanism. Atmospheric gas molecules, particularly water vapour,
have been proposed as a coolant; however, because Pluto's thermal
structure is expected to be in radiative-conductive equilibrium, the
required water vapour would need to be supersaturated by many orders of
magnitude under thermodynamic equilibrium conditions. Here we report
that atmospheric hazes, rather than gases, can explain Pluto's
temperature profile. We find that haze particles have substantially
larger solar heating and thermal cooling rates than gas molecules,
dominating the atmospheric radiative balance from the ground to an
altitude of 700 km, above which heat conduction maintains an isothermal
atmosphere. We conclude that Pluto's atmosphere is unique amongst Solar
System planetary atmospheres, as its radiative energy equilibrium is
controlled primarily by haze particles instead of gas molecules. We
predict that Pluto is therefore several orders of magnitude brighter at
mid-infrared wavelengths than previously thought - a brightness that
could be detected by future telescopes.
Published in:
Nature, 551, 352 (2017 November 16)
Available on the web at https://www.nature.com/articles/nature24465
A Search for Temporal Changes on Pluto and Charon
J.D. Hofgartner1, B.J. Buratti1, S.L. Devins1, R.A. Beyer2,3, P. Schenk4,
S.A. Stern5, H.A. Weaver6, C.B. Olkin5, A. Cheng6, K. Ennico3, T.R. Lauer7,
W.B. McKinnon8, J. Spencer5, L.A. Young5, and the New Horizons Science Team
1 Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA
2 Sagan Center at the SETI Institute, Mountain View, CA, USA
3 NASA Ames Research Center, Moffett Field, CA, USA
4 Lunar and Planetary Institute, Houston, TX, USA
5 Southwest Research Institute, Boulder, CO, USA
6 Johns Hopkins University Applied Physics Laboratory, Laurel, MD, USA
7 National Optical Astronomy Observatory, Tucson, AZ, USA
8 Washington University in St. Louis, Saint Louis, MO, USA
A search for temporal changes on Pluto and Charon was motivated by (1)
the discovery of young surfaces in the Pluto system that imply ongoing
or recent geologic activity, (2) the detection of active plumes on
Triton during the Voyager 2 flyby, and (3) the abundant and detailed
information that observing geologic processes in action provides about
the processes. A thorough search for temporal changes using New
Horizons images was completed. Images that covered the same region were
blinked and manually inspected for any differences in appearance. The
search included full-disk images such that all illuminated regions of
both bodies were investigated and higher resolution images such that
parts of the encounter hemispheres were investigated at finer spatial
scales. Changes of appearance between different images were observed
but in all cases were attributed to variability of the imaging
parameters (especially geometry) or artifacts. No differences of
appearance that are strongly indicative of a temporal change were found
on the surface or in the atmosphere of either Pluto or Charon. Limits
on temporal changes as a function of spatial scale and temporal interval
during the New Horizons encounter are determined. The longest time
interval constraint is one Pluto/Charon rotation period ( ≈ 6.4
Earth days). Contrast reversal and high-phase bright features that
change in appearance with solar phase angle are identified. The change
of appearance of these features is most likely due to the change in
phase angle rather than a temporal change. Had active plumes analogous
to the plumes discovered on Triton been present on the encounter
hemispheres of either Pluto or Charon, they would have been detected.
The absence of active plumes may be due to temporal variability (i.e.,
plumes do occur but none were active on the encounter hemispheres during
the epoch of the New Horizons encounter) or because plumes do not occur.
Several dark streak features that may be deposits from past plumes are
identified.
Published in:
Icarus, 302, 273 (2018 March 1)
For preprints, on the web at https://arxiv.org/abs/1711.02750
Ices on Charon: Distribution of H2O and NH3 from New Horizons LEISA observations
C. Morea Dalle Ore1,2, S. Protopapa3, J.C. Cook4, W.M. Grundy5,
D.P. Cruikshank1, A.J. Verbiscer6, K. Ennico1, C.B. Olkin7,
S.A. Stern7, H.A. Weaver8, L.A. Young7, and the New Horizons Science Team
1 NASA Ames Research Center, Moffett Field, CA 94035-1000, USA
2 Carl Sagan Center, SETI Institute, 189 Bernardo Ave., Mountain View, CA 94043, USA
3 University of Maryland, Department of Astronomy, College Park, MD 20742, USA
4 Pinhead Institute, Telluride, CO, USA
5 Lowell Observatory, Flagstaff, AZ 86001, USA
6 University of Virginia, Charlottesville, VA, USA
7 Southwest Research Institute, Boulder, CO, USA
8 John Hopkins University, Applied Physics Laboratory, Laurel, MD, USA
Charon, the largest moon of Pluto, appeared as a fairly homogeneous, gray, icy world to New Horizons
during closest approach on July 14th, 2015. Charon's sub-Pluto hemisphere was scanned by the Ralph/LEISA
near-IR spectrograph providing an unprecedented opportunity to measure its surface composition.
We apply a statistical clustering tool to identify spectrally distinct terrains and a radiative transfer
approach to study the variations of the 2.0-μm H
2O ice band. We map the distribution of the ices
previously reported to be present on Charon's surface, namely H
2O and the products of NH
3 in H
2O.
We find that H
2O ice is mostly in the crystalline phase, confirming previous studies. The regions with
the darkest albedos show the strongest signature of amorphous-phase ice, although the crystalline component
is still strong. The brighter albedo regions, often corresponding to crater ejecta blankets, are characterized
by larger H
2O grains, possibly an indication of a younger age. We observe two different behaviors for
the two absorption bands representing NH
3 in H
2O. The 2.21-μm band tends to cluster more in
the northern areas compared to the ≈ 2.01-μm band. Both bands are present in the brighter
crater rays, but not all craters show both bands. The 2.21-μm band is also clearly present on the
smaller moons Hydra and Nix. These results hint that different physical conditions may determine the appearance
or absence of these two different forms of NH
3 in H
2O ice in the Pluto system. We also investigate the
blue slope affecting the spectrum at wavelengths longer than ∼ 1.8 μm previously reported by several
authors. We find that the slope is common among the objects in the Pluto system, Charon, the smaller moons
Nix and Hydra, and the darkest terrains on Pluto. It also characterizes the analog ice tholin obtained from
irradiation of Pluto-specific materials (a mixture of N
2, CH
4, and CO ices) in the laboratory. Our
modeling results show that Pluto ice tholins are widespread almost uniformly on Charon suggesting a common
distribution possibly part of the original reservoir of materials that made up Charon. This was irradiated
over the years to yield the gray color characteristic of Charon today. On top of the `primordial' Pluto ice
tholin there is the redder component produced by irradiation of the CH
4 provided by Pluto’s atmospheric
contribution as illustrated by Grundy et al. (2016, Nature 539, 65).
Published in:
Icarus, 300, 21 (2018 January 15)
For preprints, contact Cristina.M.DalleOre@nasa.gov
or on the web at http://adsabs.harvard.edu/abs/2018Icar..300...21D
PAPERS RECENTLY SUBMITTED TO JOURNALS |
|
Chaotic Dynamics in the (47171) Lempo Triple System
Alexandre C. M. Correia1,2
1 CIDMA, Dep. Física, Univ. Aveiro, Campus de Santiago, 3810-193 Aveiro, Portugal
2 ASD, IMCCE-CNRS, Observatoire de Paris, 77 Av. Denfert-Rochereau, 75014 Paris, France
We investigate the dynamics of the (47171) Lempo triple system, also
known by 1999 TC
36. We derive a full 3D N-body model that takes
into account the orbital and spin evolution of all bodies, which are
assumed triaxial ellipsoids. We show that, for reasonable values of the
shapes and rotational periods, the present best fitted orbital solution
is chaotic and unstable in short time-scales. The formation mechanism of
this system is unknown, but the orbits can be stabilised when tidal
dissipation is taken into account. The dynamics of this system is very
rich, but depends on many parameters that are presently unknown. A
better understanding of this systems thus requires more observations,
which also need to be fitted with a complete model like the one
presented here.
Submitted to:
Icarus
For preprints, contact correia@ua.pt
or on the web at http://arxiv.org/abs/1710.08401
Chaotic Dynamics of Trans-Neptunian Objects Perturbed by Planet Nine
Sam Hadden1, Gongjie Li1, Matthew J. Payne1, and Matthew J. Holman1
1 Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS 51, Cambridge, MA 02138, USA
Observations of clustering among the orbits of the most distant
trans-Neptunian objects (TNOs) has inspired interest in the possibility
of an undiscovered ninth planet lurking in the outskirts of the solar
system (Trujillo & Sheppard 2014; Batygin & Brown 2016a). Numerical
simulations by a number of authors have demonstrated that, with
appropriate choices of planet mass and orbit, such a planet can maintain
clustering in the orbital elements of the population of distant TNOs,
similar to the observed sample. However, many aspects of the rich
underlying dynamical processes induced by such a distant eccentric
perturber have not been fully explored. We report the results of our
investigation of the dynamics of coplanar test-particles which interact
with a massive body on an circular orbit (Neptune) and a massive body
on a more distant, highly eccentric orbit (the putative Planet Nine). We
find that a detailed examination of our idealized simulations affords
tremendous insight into the rich test-particle dynamics that are
possible. In particular, we find that chaos and resonance overlap plays
an important role in particles' dynamical evolution. We develop a simple
mapping model that allows us to understand in detail the web of
overlapped mean-motion resonances explored by chaotically evolving
particles. We also demonstrate that gravitational interactions with
Neptune can have profound effect on the orbital evolution of particles.
Our results serve as a starting point for a better understanding of the
dynamical behavior observed in more complicated simulations that can be
used to constrain the mass and orbit of Planet Nine.
Submitted to:
AAS Journals
Preprints available on the web at https://arxiv.org/abs/1712.06547
Concentrating Small Particles in Protoplanetary Disks through
the Streaming Instability
C.C. Yang1, A. Johansen1, and D. Carrera1
1 Lund Observatory, Department of Astronomy and Theoretical Physics,
Lund University, Box 43, 221 00 Lund, Sweden
Laboratory experiments indicate that direct growth of silicate grains
via mutual collisions can only produce particles up to roughly
millimeters in size. On the other hand, recent simulations of the
streaming instability have shown that mm/cm-sized particles require an
excessively high metallicity for dense filaments to emerge. Using a
numerical algorithm for stiff mutual drag force, we perform simulations
of small particles with significantly higher resolutions and longer
simulation times than in previous investigations. We find that particles
of dimensionless stopping time τ
s = 10
−2 and 10
−3
- representing cm- and mm-sized particles interior of the water ice
line - concentrate themselves via the streaming instability at a solid
abundance of a few percent. We thus revise a previously published
critical solid abundance curve for the regime of τ
s << 1. The solid density in the concentrated regions reaches values higher
than the Roche density, indicating that direct collapse of particles
down to mm sizes into planetesimals is possible. Our results hence
bridge the gap in particle size between direct dust growth limited by
bouncing and the streaming instability.
Published in:
Astronomy and Astrophysics, 606, A80
Preprints are available at https://arxiv.org/abs/1611.07014
Scientific Workshop on the Transneptunian Solar System
2018 March 26-29
Coimbra, Portugal
This scientific workshop highlights the current knowledge and understanding
of the Transneptunian Solar System. We invite you to register for the meeting and to
propose contributed papers for the workshop sessions. The deadline for registration
and abstract submissions is 2018 January 20. Presentations will cover the following topics:
- Physical properties of TNOs: Interior, surface, atmosphere
- The large TNOs: Pluto and others
- Satellites - Binaries and multiple systems
- Formation and evolution processes: Origin, planetesimals, multiples, dynamical and collisional evolution, physical processing
- Relationships with other populations: Centaurs, planetary Trojans, comets, Inner Oort Cloud
- Planet IX and related TNOs - Dynamical effects, indicators, properties
- Extra-solar KBO populations: Structure, properties
- Prospects for KBO research
The number of workshop participants is limited to 100 persons.
Details on the workshop framework (SOC, LOC, invited speakers,
deadlines, venue, and travel and hotel information) as well as access for
registration, hotel booking and abstract submission can be found at
http://www2.mps.mpg.de/services/coimbra/
Newsletter Information
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Distant EKOs Newsletter is dedicated to provide researchers with
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Distant EKOs is not a refereed publication, but is a tool for
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