Previously, the policy of Distant EKOs was, for those papers that had been submitted to journals but not yet accepted, to publish them in the newsletter as ``title only'' (with author list and link to preprints). Starting with this issue, I am changing the policy of the newsletter so that full abstracts will be published for papers submitted to refereed publications.
The Herschel "TNOs are cool" program (photometry of 130 TNOs at thermal
wavelengths) is now virtually finished. Results (observing circumstances, fluxes,
radiometric solutions) can be found at:
http://public-tnosarecool.lesia.obspm.fr/
There were 11 new TNO discoveries announced since the previous issue of Distant EKOs:
2006 SE415, 2006 SF415, 2007 FM51, 2007 RW326, 2007 RX326, 2007 RY326, 2014 MT69, 2014 MU69, 2014 OS393, 2014 PN70, 2015 FP36
and 6 new Centaur/SDO discoveries:
2007 FN51, 2007 LE38, 2007 LF38, 2008 JO41, 2015 DB216, 2015 FZ117
Reclassified objects:
2015 DB216 (SDOCentaur)
Objects recently assigned numbers:
2015 BQ311 = (433873)
2012 HH2 = (432949)
Current number of TNOs: 1365 (including Pluto)
Current number of Centaurs/SDOs: 441
Current number of Neptune Trojans: 12
Out of a total of 1818 objects:
669 have measurements from only one opposition
637 of those have had no measurements for more than a year
329 of those have arcs shorter than 10 days
(for more details, see:
http://www.boulder.swri.edu/ekonews/objects/recov_stats.jpg)
Chondrules are millimeter-sized spherules that dominate primitive meteorites
(chondrites) originating from the asteroid belt. The incorporation of
chondrules into asteroidal bodies must be an important step in planet
formation, but the mechanism is not understood. We show that the main growth of
asteroids can result from gas-drag-assisted accretion of chondrules. The
largest planetesimals of a population with a characteristic radius of 100 km
undergo run-away accretion of chondrules within 
3 Myr, forming planetary
embryos up to Mars sizes along with smaller asteroids whose size distribution
matches that of main belt asteroids. The aerodynamical accretion leads to
size-sorting of chondrules consistent with chondrites. Accretion of mm-sized
chondrules and ice particles drives the growth of planetesimals beyond the ice
line as well, but the growth time increases above the disk life time outside of
25 AU. The contribution of direct planetesimal accretion to the growth of both
asteroids and Kuiper belt objects is minor. In contrast, planetesimal accretion
and chondrule accretion play more equal roles for the formation of Moon-sized
embryos in the terrestrial planet formation region. These embryos are isolated
from each other and accrete planetesimals only at a low rate. However, the
continued accretion of chondrules destabilizes the oligarchic configuration and
leads to the formation of Mars-sized embryos and terrestrial planets by a
combination of direct chondrule accretion and giant impacts.
To appear in: Science Advances
Preprints available on the web at http://arxiv.org/abs/1503.07347
We present the first photometric observations of trans-Neptunian objects (TNOs) taken with the Kepler space telescope, obtained in the course of the K2 ecliptic survey. Two faint objects have been monitored in specifically designed pixel masks that were centered on the stationary points of the objects, when their daily motion was the slowest. In the design of the experiment, only the apparent path of these objects were retrieved from the detectors, i.e. the costs in terms of Kepler pixels were minimized. Because of the faintness of the targets we employ specific reduction techniques and co-added images. We measure rotational periods and amplitudes in the unfiltered Kepler band as follows: for (278361) 2007 JJ43 and 2002 GV31 we get Prot = 12.097 h and Prot = 29.2 h while 0.10 and 0.35 mag for the total amplitudes, respectively. Future space missions, like TESS and PLATO are not well suited to this kind of observations. Therefore, we encourage to include the brightest TNOs around their stationary points in each observing campaign to exploit this unique capability of the K2 Mission - and therefore to provide unbiased rotational, shape and albedo characteristics of many objects.
To appear in: The Astrophysical Journal Letters
For preprints, contact apal@szofi.net
or on the web at http://arxiv.org/abs/1504.03671
and http://szofi.net/apal/astro/k2/tno/
Observations indicate that some of the largest Kuiper Belt Objects
(KBOs) have retained volatiles in the gas phase, which implies the
presence of an atmosphere that can affect their reflectance spectra and
thermal balance. Volatile escape rates driven by solar heating of the
surface were estimated by Schaller and Brown (2007) (SB) and Levi and
Podolak (2009) (LP) using Jeans escape from the surface and a
hydrodynamic model respectively. Based on recent molecular kinetic
simulations these rates can be hugely in error (e.g., a factor of 
for the SB estimate for Pluto). In this paper we estimate the
loss of primordial N2 for several large KBOs guided by recent
molecular kinetic simulations of escape due to solar heating of the
surface and due to UV/EUV heating of the upper atmosphere. For the
latter we extrapolate simulations of escape from Pluto (Erwin et al.
2013) using the energy limited escape model recently validated for the
KBOs of interest by molecular kinetic simulations (Johnson et al. 2013).
Unless the N2 atmosphere is thin (
N2/cm2)
and/or the radius is small (
200-300 km), we find that
escape is primarily driven by the UV/EUV radiation absorbed in the upper
atmosphere rather than the solar heating of the surface. This affects
the previous interpretations of the relationship between atmospheric
loss and the observed surface properties. The long-term goal is to
connect detailed atmospheric loss simulations with a model for volatile
transport (e.g., Young, 2014) for individual KBOs.
Submitted to: The Astrophysical Journal
For preprints, contact apurva.oza@latmos.ipsl.fr
or on the web at http://arxiv.org/abs/1503.05315
This is a white paper, available on the web at
http://arxiv.org/abs/1503.07947v1
In this work we present the results of a suite of dynamical simulations following the orbital evolution of 8,022 hypothetical Centaur objects. These Centaurs begin our integrations on orbits in the vicinity of the 2:1 mean motion resonance with Neptune, and we follow their dynamical evolution for a period of 3 Myr under the gravitational influence of a motionless Sun and the four Jovian planets. The great majority of the test particles studied rapidly escaped from the vicinity of the 2:1 mean motion resonance of Neptune and diffused throughout the Solar System. The average libration time of Centaurs in the vicinity of 2:1 mean motion resonance of Neptune was found to be just 27 kyr. Although two particles did remain near the resonance for more than 1 Myr. Upon leaving the vicinity of the 2:1 resonance, the majority of test particles evolved by a process of random walk in semi-major axis, due to repeated close encounters with the giant planets.
To appear in: Proceedings of the 14th Annual Australian Space Research Conference
Preprints available or on the web at http://arxiv.org/abs/1503.06096
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.
