28 research outputs found
Carbon monoxide in the distantly active Centaur (60558) 174P/Echeclus at 6 AU
(60558) 174P/Echeclus is an unusual object that belongs to a class of minor
planets called Centaurs, which may be intermediate between Kuiper Belt Objects
and Jupiter Family comets. It is sporadically active throughout its orbit at
distances too far for water ice to sublimate, the source of activity for most
comets. Thus, its coma must be triggered by another mechanism. In 2005,
Echeclus had a strong outburst with peculiar behavior that raised questions
about the nucleus homogeneity. In order to test nucleus models, we performed
the most sensitive search to date for the highly volatile CO molecule via its
J=2-1 emission toward Echeclus during 2016 May-June (at 6.1 astronomical units
from the Sun) using the Arizona Radio Observatory 10-m Submillimeter Telescope.
We obtained a 3.6-sigma detection with a slightly blue-shifted (delta v = -0.55
+- 0.1 km/s) and narrow (FWHM = 0.53 +- 0.23 km/s) line. The data are
consistent with emission from a cold gas from the sunward side of the nucleus,
as seen in two other comets at 6 AU. We derive a production rate of Q(CO) =
(7.7 +- 3.3)x10^26 mol/s, which is capable of driving the estimated dust
production rates. Echeclus CO outgassing rate is ~40 times lower than what is
typically seen for another Centaur at this distance, 29P/Schwassmann-Wachmann
1. We also used the IRAM 30-m telescope to search for the CO J=2-1 line, and
derive an upper limit that is above the SMT detection. Compared to the
relatively unprocessed comet C/1995 O1 (Hale-Bopp), Echeclus produces
significantly less CO, as do Chiron and four other Centaurs.Comment: 27 pages, 3 figures, 1 table. Accepted for publication in The
Astronomical Journa
Erosive Hit-and-Run Impact Events: Debris Unbound
Erosive collisions among planetary embryos in the inner solar system can lead
to multiple remnant bodies, varied in mass, composition and residual velocity.
Some of the smaller, unbound debris may become available to seed the main
asteroid belt. The makeup of these collisionally produced bodies is different
from the canonical chondritic composition, in terms of rock/iron ratio and may
contain further shock-processed material. Having some of the material in the
asteroid belt owe its origin from collisions of larger planetary bodies may
help in explaining some of the diversity and oddities in composition of
different asteroid groups.Comment: 7 pages, 3 figure
Thermal evolution and activity of Comet 9P/Tempel 1 and simulation of a deep impact
We use a quasi 3-D thermal evolution model for a spherical comet nucleus,
which takes into account the diurnal and latitudinal variation of the solar
flux, but neglects lateral heat conduction. We model the thermal evolution and
activity of Comet 9P/Tempel 1, in anticipation of the Deep Impact mission
encounter with the comet. We also investigate the possible outcome of a
projectile impact, assuming that all the energy is absorbed as thermal energy.
An interesting result of this investigation, is that the estimated amount of
dust ejected due to the impact is equivalent to 2--2.6 days of activity, during
"quiet" conditions, at perihelion.
We show that production rates of volatiles that are released in the interior
of the nucleus depend strongly on the porous structure, in particular on the
surface to volume ratio of the pores. We develop a more accurate model for
calculating this parameter, based on a distribution of pore sizes, rather than
a single, average pore size.Comment: 25 pages, 8 figures, accepted for publication in PASP (in press). For
fig.xx (composite image, sec.4) and a better resolution of fig.6 see,
http://geophysics.tau.ac.il/personal/gal%5Fsarid
The Astropy Problem
The Astropy Project (http://astropy.org) is, in its own words, "a community
effort to develop a single core package for Astronomy in Python and foster
interoperability between Python astronomy packages." For five years this
project has been managed, written, and operated as a grassroots,
self-organized, almost entirely volunteer effort while the software is used by
the majority of the astronomical community. Despite this, the project has
always been and remains to this day effectively unfunded. Further, contributors
receive little or no formal recognition for creating and supporting what is now
critical software. This paper explores the problem in detail, outlines possible
solutions to correct this, and presents a few suggestions on how to address the
sustainability of general purpose astronomical software
Ejecta Evolution Following a Planned Impact into an Asteroid: The First Five Weeks
The impact of the DART spacecraft into Dimorphos, moon of the asteroid
Didymos, changed Dimorphos' orbit substantially, largely from the ejection of
material. We present results from twelve Earth-based facilities involved in a
world-wide campaign to monitor the brightness and morphology of the ejecta in
the first 35 days after impact. After an initial brightening of ~1.4
magnitudes, we find consistent dimming rates of 0.11-0.12 magnitudes/day in the
first week, and 0.08-0.09 magnitudes/day over the entire study period. The
system returned to its pre-impact brightness 24.3-25.3 days after impact
through the primary ejecta tail remained. The dimming paused briefly eight days
after impact, near in time to the appearance of the second tail. This was
likely due to a secondary release of material after re-impact of a boulder
released in the initial impact, through movement of the primary ejecta through
the aperture likely played a role.Comment: 16 pages, 5 Figures, accepted in the Astrophysical Journal Letters
(ApJL) on October 16, 202