2,042 research outputs found
The Thermal Evolution of Ices in the Environments of Newly Formed Stars: The CO_2 Diagnostic
Archival data from the Infrared Spectrometer of the Spitzer Space Telescope are used to study the 15 μm absorption feature of solid CO_2 toward 28 young stellar objects (YSOs) of approximately solar mass. Fits to the absorption profile using laboratory spectra enable categorization according to the degree of thermal processing of the ice matrix that contains the CO_2. The majority of YSOs in our sample (20 out of 28) are found to be consistent with a combination of polar (H_2O-rich) and nonpolar (CO-rich) ices at low temperature; the remainder exhibit profile structure consistent with partial crystallization as the result of significant heating. Ice-phase column densities of CO_2 are determined and compared with those of other species. Lines of sight with crystallization signatures in their spectra are found to be systematically deficient in solid-phase CO, as expected if CO is being sublimated in regions where the ices are heated to crystallization temperatures. Significant variation is found in the CO2 abundance with respect to both H_2O (the dominant ice constituent) and total dust column (quantified by the extinction, AV ). YSOs in our sample display typically higher CO_2 concentrations (independent of evidence for thermal processing) in comparison to quiescent regions of the prototypical cold molecular cloud. This suggests that enhanced CO_2 production is driven by photochemical reactions in proximity to some YSOs, and that photoprocessing and thermal processing may occur independently
Saturn's Exploration Beyond Cassini-Huygens
For its beautiful rings, active atmosphere and mysterious magnetic field,
Saturn is a fascinating planet. It also holds some of the keys to understanding
the formation of our Solar System and the evolution of giant planets in
general. While the exploration by the Cassini-Huygens mission has led to great
advances in our understanding of the planet and its moons, it has left us with
puzzling questions: What is the bulk composition of the planet? Does it have a
helium core? Is it enriched in noble gases like Jupiter? What powers and
controls its gigantic storms? We have learned that we can measure an outer
magnetic field that is filtered from its non-axisymmetric components, but what
is Saturn's inner magnetic field? What are the rings made of and when were they
formed? These questions are crucial in several ways: a detailed comparison of
the compositions of Jupiter and Saturn is necessary to understand processes at
work during the formation of these two planets and of the Solar System. This
calls for the continued exploration of the second largest planet in our Solar
System, with a variety of means including remote observations and space
missions. Measurements of gravity and magnetic fields very close to the
planet's cloud tops would be extremely valuable. Very high spatial resolution
images of the rings would provide details on their structure and the material
that form them. Last but not least, one or several probes sent into the
atmosphere of the planet would provide the critical measurements that would
allow a detailed comparison with the same measurements at Jupiter. [abridged
abstract
Proceedings of the 2011 New York Workshop on Computer, Earth and Space Science
The purpose of the New York Workshop on Computer, Earth and Space Sciences is
to bring together the New York area's finest Astronomers, Statisticians,
Computer Scientists, Space and Earth Scientists to explore potential synergies
between their respective fields. The 2011 edition (CESS2011) was a great
success, and we would like to thank all of the presenters and participants for
attending. This year was also special as it included authors from the upcoming
book titled "Advances in Machine Learning and Data Mining for Astronomy". Over
two days, the latest advanced techniques used to analyze the vast amounts of
information now available for the understanding of our universe and our planet
were presented. These proceedings attempt to provide a small window into what
the current state of research is in this vast interdisciplinary field and we'd
like to thank the speakers who spent the time to contribute to this volume.Comment: Author lists modified. 82 pages. Workshop Proceedings from CESS 2011
in New York City, Goddard Institute for Space Studie
Giant Planets
We review the interior structure and evolution of Jupiter, Saturn, Uranus and
Neptune, and giant exoplanets with particular emphasis on constraining their
global composition. Compared to the first edition of this review, we provide a
new discussion of the atmospheric compositions of the solar system giant
planets, we discuss the discovery of oscillations of Jupiter and Saturn, the
significant improvements in our understanding of the behavior of material at
high pressures and the consequences for interior and evolution models. We place
the giant planets in our Solar System in context with the trends seen for
exoplanets.Comment: This chapter is to be published in the second edition of the Treatise
on Geophysics (Eds. T. Spohn, G. Schubert). 42 pages, 16 figures. Accepted 25
February 201
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