3,263 research outputs found
The taxonomic distribution of asteroids from multi-filter all-sky photometric surveys
The distribution of asteroids across the Main Belt has been studied for
decades to understand the compositional distribution and what that tells us
about the formation and evolution of our solar system. All-sky surveys now
provide orders of magnitude more data than targeted surveys. We present a
method to bias-correct the asteroid population observed in the Sloan Digital
Sky Survey (SDSS) according to size, distance, and albedo. We taxonomically
classify this dataset consistent with the Bus and Bus-DeMeo systems and present
the resulting taxonomic distribution. The dataset includes asteroids as small
as 5 km, a factor of three in diameter smaller than in previous works. Because
of the wide range of sizes in our sample, we present the distribution by
number, surface area, volume, and mass whereas previous work was exclusively by
number. While the distribution by number is a useful quantity and has been used
for decades, these additional quantities provide new insights into the
distribution of total material. We find evidence for D-types in the inner main
belt where they are unexpected according to dynamical models of implantation of
bodies from the outer solar system into the inner solar system during planetary
migration (Levison et al. 2009). We find no evidence of S-types or other
unexpected classes among Trojans and Hildas, albeit a bias favoring such a
detection. Finally, we estimate for the first time the total amount of material
of each class in the inner solar system. The main belt's most massive classes
are C, B, P, V and S in decreasing order. Excluding the four most massive
asteroids, Ceres, Pallas, Vesta and Hygiea that heavily skew the values,
primitive material (C-, P-types) account for more than half main-belt and
Trojan asteroids by mass, most of the remaining mass being in the S-types. All
the other classes are minor contributors to the material between Mars and
Jupiter.Comment: Accepted for publication in Icarus -- 43 pages, 15 figures, 7 table
Systematic ranging and late warning asteroid impacts
We describe systematic ranging, an orbit determination technique especially
suitable to assess the near-term Earth impact hazard posed by newly discovered
asteroids. For these late warning cases, the time interval covered by the
observations is generally short, perhaps a few hours or even less, which leads
to severe degeneracies in the orbit estimation process. The systematic ranging
approach gets around these degeneracies by performing a raster scan in the
poorly-constrained space of topocentric range and range rate, while the plane
of sky position and motion are directly tied to the recorded observations. This
scan allows us to identify regions corresponding to collision solutions, as
well as potential impact times and locations. From the probability distribution
of the observation errors, we obtain a probability distribution in the orbital
space and then estimate the probability of an Earth impact. We show how this
technique is effective for a number of examples, including 2008 TC3 and 2014
AA, the only two asteroids to date discovered prior to impact
The Pan-STARRS Moving Object Processing System
We describe the Pan-STARRS Moving Object Processing System (MOPS), a modern
software package that produces automatic asteroid discoveries and
identifications from catalogs of transient detections from next-generation
astronomical survey telescopes. MOPS achieves > 99.5% efficiency in producing
orbits from a synthetic but realistic population of asteroids whose
measurements were simulated for a Pan-STARRS4-class telescope. Additionally,
using a non-physical grid population, we demonstrate that MOPS can detect
populations of currently unknown objects such as interstellar asteroids.
MOPS has been adapted successfully to the prototype Pan-STARRS1 telescope
despite differences in expected false detection rates, fill-factor loss and
relatively sparse observing cadence compared to a hypothetical Pan-STARRS4
telescope and survey. MOPS remains >99.5% efficient at detecting objects on a
single night but drops to 80% efficiency at producing orbits for objects
detected on multiple nights. This loss is primarily due to configurable MOPS
processing limits that are not yet tuned for the Pan-STARRS1 mission.
The core MOPS software package is the product of more than 15 person-years of
software development and incorporates countless additional years of effort in
third-party software to perform lower-level functions such as spatial searching
or orbit determination. We describe the high-level design of MOPS and essential
subcomponents, the suitability of MOPS for other survey programs, and suggest a
road map for future MOPS development.Comment: 57 Pages, 26 Figures, 13 Table
(1173) Anchises - Thermophysical and Dynamical Studies of a Dynamically Unstable Jovian Trojan
We have performed detailed thermophysical and dynamical modelling of Jovian
Trojan (1173) Anchises. Our results reveal a most unusual object. By examining
observational data taken by IRAS, Akari and WISE between 11.5 and 60 microns,
along with variations in its optical lightcurve, we find Anchises is most
likely an elongated body, with an axes-ratio of ~1.4. This yields calculated
best-fit dimensions of 170x121x121km (an equivalent diameter of 136+18/-11km).
We find the observations are best fit by Anchises having a retrograde sense of
rotation, and an unusually high thermal inertia (25 to 100 Jm-2s-0.5K-1). The
geometric albedo is found to be 0.027 (+0.006/-0.007). Anchises therefore has
one of the highest published thermal inertias of any object larger than 100km
in diameter, at such large heliocentric distances, and is one of the lowest
albedo objects ever observed. More observations are needed to see if there is a
link between the very shallow phase curve, with almost no opposition effect,
and the derived thermal properties for this large Trojan asteroid. Our
dynamical investigation of Anchises' orbit has revealed it to be dynamically
unstable on timescales of hundreds of Myr, similar to the unstable Neptunian
Trojans 2001 QR322 and 2008 LC18. Unlike those objects, we find that Anchises'
dynamical stability is not a function of its initial orbital elements, the
result of the exceptional precision with which its orbit is known. This is the
first time that a Jovian Trojan has been shown to be dynamically unstable, and
adds weight to the idea that planetary Trojans represent a significant ongoing
contribution to the Centaur population, the parents of the short-period comets.
The observed instability does not rule out a primordial origin for Anchises,
but when taken in concert with the result of our thermophysical analysis,
suggest that it would be a fascinating target for future study.Comment: 5 figures, 3 tables, accepted for publication in Monthly Notices of
the Royal Astronomical Societ
Preliminary Results from NEOWISE: An Enhancement to the Wide-field Infrared Survey Explorer for Solar System Science
The Wide-field Infrared Survey Explorer (WISE) has surveyed the entire sky at four infrared wavelengths with greatly improved sensitivity and spatial resolution compared to its predecessors, the Infrared Astronomical Satellite and the Cosmic Background Explorer. NASA's Planetary Science Division has funded an enhancement to the WISE data processing system called "NEOWISE" that allows detection and archiving of moving objects found in the WISE data. NEOWISE has mined the WISE images for a wide array of small bodies in our solar system, including near-Earth objects (NEOs), Main Belt asteroids, comets, Trojans, and Centaurs. By the end of survey operations in 2011 February, NEOWISE identified over 157,000 asteroids, including more than 500 NEOs and ~120 comets. The NEOWISE data set will enable a panoply of new scientific investigations
The astrometric Gaia-FUN-SSO observation campaign of 99 942 Apophis
Astrometric observations performed by the Gaia Follow-Up Network for Solar
System Objects (Gaia-FUN-SSO) play a key role in ensuring that moving objects
first detected by ESA's Gaia mission remain recoverable after their discovery.
An observation campaign on the potentially hazardous asteroid (99 942) Apophis
was conducted during the asteroid's latest period of visibility, from
12/21/2012 to 5/2/2013, to test the coordination and evaluate the overall
performance of the Gaia-FUN-SSO . The 2732 high quality astrometric
observations acquired during the Gaia-FUN-SSO campaign were reduced with the
Platform for Reduction of Astronomical Images Automatically (PRAIA), using the
USNO CCD Astrograph Catalogue 4 (UCAC4) as a reference. The astrometric
reduction process and the precision of the newly obtained measurements are
discussed. We compare the residuals of astrometric observations that we
obtained using this reduction process to data sets that were individually
reduced by observers and accepted by the Minor Planet Center. We obtained 2103
previously unpublished astrometric positions and provide these to the
scientific community. Using these data we show that our reduction of this
astrometric campaign with a reliable stellar catalog substantially improves the
quality of the astrometric results. We present evidence that the new data will
help to reduce the orbit uncertainty of Apophis during its close approach in
2029. We show that uncertainties due to geolocations of observing stations, as
well as rounding of astrometric data can introduce an unnecessary degradation
in the quality of the resulting astrometric positions. Finally, we discuss the
impact of our campaign reduction on the recovery process of newly discovered
asteroids.Comment: Accepted for publication in A&
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