LSST Solar System Science Collaboration
Over its 10 year lifespan, the Large Synoptic Sky Survey Telescope (LSST) will catalog over 5 million Main Belt asteroids, almost 300,000 Jupiter Trojans, over 100,000 NEOs, and over 40,000 KBOs. Many of these objects will receive 100s of observations in multiple bandpasses. The LSST Solar System Science Collaboration (SSSC) is preparing methods and tools to analyze this data, as well as understand optimum survey strategies for discovering moving objects throughout the Solar System.
The SSSC launched a new website. Check it out at
http://www.lsstsssc.org, and please consider joining the
collaboration if you're an eligible researcher. If you have any
questions, please contact the SSSC Co-Chairs,
Meg Schwamb (mschwamb.astro@gmail.com) and
David Trilling
(David.Trilling@nau.edu).
There were no new TNO discoveries announced since the previous issue of Distant EKOs, but there were 10 new Centaur/SDO discoveries:
2013 RQ98, 2013 RR98, 2013 UT15, 2014 UN225, 2015 GT50, 2015 KG163, 2015 KH163, 2015 RX245, 2015 RY245, 2017 NM2
Reclassified objects:
2011 JA32 (SDOTNO)
Objects recently assigned numbers:
2012 VS113 = (495190)
2013 TJ159 = (495297)
2015 AM281 = (495603)
2012 VR113 = (495189)
2015 FG345 = (495613)
2013 GP136 = (496315)
Current number of TNOs: 1816 (including Pluto)
Current number of Centaurs/SDOs: 715
Current number of Neptune Trojans: 17
Out of a total of 2548 objects:
706 have measurements from only one opposition
699 of those have had no measurements for more than a year
344 of those have arcs shorter than 10 days
(for more details, see:
http://www.boulder.swri.edu/ekonews/objects/recov_stats.jpg)
The accumulating but small set of large semimajor axis trans-Neptunian objects (TNOs) shows an apparent clustering in the orientations of their orbits. This clustering must either be representative of the intrinsic distribution of these TNOs, or else have arisen as a result of observation biases and/or statistically expected variations for such a small set of detected objects. The clustered TNOs were detected across different and independent surveys, which has led to claims that the detections are therefore free of observational bias. This apparent clustering has led to the so-called ``Planet 9'' hypothesis that a super-Earth currently resides in the distant solar system and causes this clustering. The Outer Solar System Origins Survey (OSSOS) is a large program that ran on the Canada-France-Hawaii Telescope from 2013 to 2017, discovering more than 800 new TNOs. One of the primary design goals of OSSOS was the careful determination of observational biases that would manifest within the detected sample. We demonstrate the striking and non-intuitive biases that exist for the detection of TNOs with large semimajor axes. The eight large semimajor axis OSSOS detections are an independent data set, of comparable size to the conglomerate samples used in previous studies. We conclude that the orbital distribution of the OSSOS sample is consistent with being detected from a uniform underlying angular distribution.
Published in: The Astronomical Journal, 154, 50 (2017 August)
Preprints available on the web at https://arxiv.org/abs/1706.05348
and https://doi.org/10.3847/1538-3881/aa7aed
The hypothesis that a massive Planet Nine exists in the outer solar system on a distant eccentric orbit was inspired by observations showing that the objects with the most distant eccentric orbits in the Kuiper Belt have orbits that are physically aligned, that is, they are clustered in longitude of perihelion and have similar orbital planes. Questions have remained, however, about the effects of observational bias on these observations, particularly on the longitudes of perihelion. Specifically, distant eccentric Kuiper Belt objects (KBOs) tend to be faint and only observable near their perihelia, suggesting that the longitudes of perihelion of the known distant objects could be strongly biased by the limited number of locations in the sky where deep surveys have been carried out. We have developed a method to rigorously estimate the bias in longitude of perihelion for Kuiper Belt observations. We find that the probability that the 10 known KBOs with semimajor axis beyond 230 au are drawn from a population with uniform longitude of perihelion is 1.2%. Combined with the observation that the orbital poles of these objects are also clustered, the overall probability of detecting these two independent clusterings in a randomly distributed sample is 0.025%. While observational bias is clearly present in these observations, it is unlikely to explain the observed alignment of the distant eccentric KBOs.
Published in: The Astronomical Journal, 154, 65 (2017 August)
Preprints available on the web at https://arxiv.org/abs/1706.04175
and https://doi.org/10.3847/1538-3881/aa79f4
It is a well-known fact that the presence of a massive perturber interacting with a population of minor bodies following very eccentric orbits can strongly affect the distribution of their nodal distances. The details of this process have been explored numerically and its outcome confirmed observationally in the case of Jupiter, where a bimodal distribution of nodal distances of comets has been found. Here, we show evidence for a possible bimodal distribution of the nodal distances of the extreme trans-Neptunian objects (ETNOs) in the form of a previously unnoticed correlation between nodal distance and orbital inclination. This proposed correlation is unlikely to be the result of observational bias as data for both large semimajor axis Centaurs and comets fit well into the pattern found for the ETNOs, and all these populations are subjected to similar background perturbations when moving well away from the influence of the giant planets. The correlation found is better understood if these objects tend to avoid a putative planet with semimajor axis in the range 300-400 au.
Published in: Monthly Notices of the Royal Astronomical Society, 471, L61
For preprints, contact nbplanet@ucm.es
or on the web at https://arxiv.org/abs/1706.06981
and https://doi.org/10.1093/mnrasl/slx106
We use a secular model to describe the non-resonant dynamics of trans-Neptunian objects in the presence of an external ten-earth-mass perturber. The secular dynamics is analogous to an ``eccentric Kozai mechanism'' but with both an inner component (the four giant planets) and an outer one (the eccentric distant perturber). By the means of Poincaré sections, the cases of a non-inclined or inclined outer planet are successively studied, making the connection with previous works. In the inclined case, the problem is reduced to two degrees of freedom by assuming a non-precessing argument of perihelion for the perturbing body.
The size of the perturbation is typically ruled by the semi-major axis
of the small body: we show that the classic integrable picture is still
valid below about 70 AU, but it is progressively destroyed when we get
closer to the external perturber. In particular, for a>150 AU,
large-amplitude orbital flips become possible, and for a>200 AU, the
Kozai libration islands at 
and 
are totally
submerged by the chaotic sea. Numerous resonance relations are
highlighted. The most large and persistent ones are associated to
apsidal alignments or anti-alignments with the orbit of the distant
perturber.
To appear in: Celestial Mechanics and Dynamical Astronomy
For preprints, contact melaine.saillenfest@obspm.fr
or on the web at https://arxiv.org/abs/1707.01379
Capture in mean motion resonance has been observed in the Solar System
for small objects with prograde as well as retrograde orbits of moderate
inclinations. However, no example of an object with a nearly polar orbit
was known to be in resonance with a planet. In this Letter, we report
that the nearly-polar transneptunian object (471325), nicknamed Niku,
is in a 7:9 resonance with Neptune, with a mean lifetime in resonance of
million years. While entrance and exit in the 7:9 resonance
is caused by close encounters with Neptune the resonant configuration
provides a temporary protection mechanism against disruptive close
encounters with this planet. The other nearly polar transneptunian
objects do not seem to be in resonance with the planets with the
possible exception of 2008 KV42, also known as Drac, that has a small
chance of being in the 8:13 resonance with Neptune.
To appear in: Monthly Notices of the Royal Astronomical Society
Preprints available on the web at https://arxiv.org/abs/1708.00346
and https://doi.org/10.1093/mnrasl/slx125
The classical disturbing function of the three-body problem is based on
an expansion of the gravitational interaction in the vicinity of nearly
coplanar orbits. Consequently, it is not suitable for the identification
and study of resonances of the Centaurs and transneptunian objects on
nearly polar orbits with the Solar system planets. Here, we provide a
series expansion algorithm of the gravitational interaction in the
vicinity of polar orbits and produce explicitly the disturbing function
to fourth order in eccentricity and inclination cosine. The properties
of the polar series differ significantly from those of the classical
disturbing function: the polar series can model any resonance, as the
expansion order is not related to the resonance order. The powers of
eccentricity and inclination of the force amplitude of a p:q resonance
do not depend on the value of the resonance order |p - q| but only on
its parity. Thus, all even resonance order eccentricity amplitudes are
and odd ones 
to lowest order in eccentricity
e. With the new findings on the structure of the polar disturbing
function and the possible resonant critical arguments, we illustrate the
dynamics of the polar resonances 1:3, 3:1, 2:9 and 7:9 where
transneptunian object 471325 could currently be locked.
Published in: Monthly Notices of the Royal Astronomical Society, 471, 2097
Preprints available on the web at https://arxiv.org/abs/1707.02431
and https://doi.org/10.1093/mnras/stx1714
We present results derived from four stellar occultations by the plutino
object (208996) 2003 AZ84, detected on 2011 January 8 (single-chord
event), 2012 February 3 (multi-chord), 2013 December 2 (single-chord),
and 2014 November 15 (multi-chord). Our observations rule out an oblate
spheroid solution for 2003 AZ84's shape. Instead, assuming
hydrostatic equilibrium, we find that a Jacobi triaxial solution with
semiaxes (
km can
better account for all our occultation observations. Combining these
dimensions with the rotation period of the body (6.75 hr) and the
amplitude of its rotation light curve, we derive a density
g cm-3, a geometric albedo
. A grazing
chord observed during the 2014 occultation reveals a topographic feature
along 2003 AZ84's limb, which can be interpreted as an abrupt chasm
of width 
23 km and depth >8 km, or a smooth depression of
width 80 km and depth 13 km (or an intermediate feature
between those two extremes).
Published in: The Astronomical Journal, 154, 22 (2017 July)
For preprints, contact bruno.sicardy@obspm.fr
or on the web at https://arxiv.org/abs/1705.10895
and http://iopscience.iop.org/article/10.3847/1538-3881/aa74e9
We report photometric observations of the trans-Neptunian object
2004 TT357 obtained in 2015 and 2017 using the 4.3 m Lowell's
Discovery Channel Telescope. We derive a rotational period of
7.79
0.01 h and a peak-to-peak lightcurve amplitude of
0.760.03 mag. 2004 TT357 displays a large variability that can
be explained by a very elongated single object or can be due to a
contact/close binary. The most likely scenario is that 2004 TT357
is a contact binary. If it is in hydrostatic equilibrium, we find that
the lightcurve can be explained by a system with a mass ratio
q
0.05, and a density of 
g cm-3, or
less likely a system with q
0.05, and
=5 g cm-3. Considering a single triaxial ellipsoid in
hydrostatic equilibrium, we derive a lower limit to the density of
0.78 g cm-3, and an elongation (a/b) of 2.01 assuming an equatorial
view. From Hubble Space Telescope data, we report no resolved
companion orbiting 2004 TT357. Despite an expected high fraction of
contact binaries in the trans-Neptunian belt, 2001 QG298 is the
unique confirmed contact binary in the trans-Neptunian belt, and
2004 TT357 is only the second candidate to this class of systems,
with 2003 SQ317.
Published in: The Astrophysical Journal, 844, 135 (2017 August 1)
For preprints, contact thirouin@lowell.edu
or on the web at https://arxiv.org/abs/1707.09927
and http://iopscience.iop.org/article/10.3847/1538-4357/aa7ed3
Several different classes of trans-Neptunian objects (TNOs) have been
identified based on their optical and near-infrared colors. As part of
the Colours of the Outer Solar System Origins Survey, we have obtained
g, r, and z band photometry of 26 TNOs using Subaru and Gemini
Observatories. Previous color surveys have not utilized z band
reflectance, and the inclusion of this band reveals significant surface
reflectance variations between sub-populations. The colors of TNOs in
g-r and r-z show obvious structure, and appear consistent with the
previously measured bi-modality in g-r. The distribution of colors of
the two dynamically excited surface types can be modeled using the
two-component mixing models from Fraser & Brown (2012). With the
combination of g-r and r-z, the dynamically excited classes can be
separated cleanly into red and neutral surface classes. In g - r and
r - z, the two dynamically excited surface groups are also clearly
distinct from the cold classical TNO surfaces, which are red, with
and
, while all dynamically excited
objects with similar g-r colors exhibit redder r-z colors. The z
band photometry makes it possible for the first time to differentiate
the red excited TNO surfaces from the red cold classical TNO surfaces.
The discovery of different r-z colors for these cold classical TNOs
makes it possible to search for cold classical surfaces in other regions
of the Kuiper belt and to completely separate cold classical TNOs from
the dynamically excited population, which overlaps in orbital parameter
space.
To appear in: The Astronomical Journal
Preprints available on the web at http://arxiv.org/abs/1708.03079
In this paper we present visible range light curves of the irregular Uranian satellites Sycorax, Caliban, Prospero, Ferdinand and Setebos taken with Kepler Space Telescope in the course of the K2 mission. Thermal emission measurements obtained with the Herschel/PACS and Spitzer/MIPS instruments of Sycorax and Caliban were also analysed and used to determine size, albedo and surface characteristics of these bodies. We compare these properties with the rotational and surface characteristics of irregular satellites in other giant planet systems and also with those of main belt and Trojan asteroids and trans-Neptunian objects. Our results indicate that the Uranian irregular satellite system likely went through a more intense collisional evolution than the irregular satellites of Jupiter and Saturn. Surface characteristics of Uranian irregular satellites seems to resemble the Centaurs and trans-Neptunian objects more than irregular satellites around other giant planets, suggesting the existence of a compositional discontinuity in the young Solar system inside the orbit of Uranus.
To appear in: The Astronomical Journal
Preprints available on the web at https://arxiv.org/abs/1706.06837
Dear Colleagues,
We are planning an international science conference on the Pluto system and the Kuiper Belt to be held July 15-19, 2019 at the Johns Hopkins University Applied Physics Laboratory in Laurel, MD, USA.
Please mark your calendars accordingly!
This conference will provide an opportunity to summarize our understanding of the Pluto system and the Kuiper belt following the New Horizons encounters with the Pluto system and 2014 MU69. Contributions spanning all relevant research on the Kuiper belt, including both observations and theory, will be solicited.
The conference will also serve as a nucleus for a forthcoming volume Pluto After New Horizons in the University of Arizona Space Science Series. With a projected 2020 publication date, this new book will be the successor to Pluto-Charon published in 1997.
A registration website with further details will be set up next summer, approximately one year prior to the conference.
Again, please put this conference on your calendar and join us at the Kossiakoff Center at APL in mid-July 2019!
With best regards,
Hal Weaver (JHU-APL), Alan Stern (SwRI), Rick Binzel (MIT), on behalf of the SOC
For further information, contact hal.weaver@jhuapl.edu
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.
