The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Nuanwan Sanguansak - One of the best experts on this subject based on the ideXlab platform.
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exoplanetary atmosphere target selection in the era of comparative Planetology
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: J S Morgan, E Kerins, S Awiphan, Iain Mcdonald, J J Hayes, S Komonjinda, D Mkritchian, Nuanwan SanguansakAbstract:Large-scale transit surveys such as NGTS, TESS and PLATO promise to deliver a wealth of potential targets for follow-up transmission spectroscopy study. This will usher in an era of comparative Planetology that will be limited not by a paucity of targets but by the scarcity of follow-up assets on the ground and in space. It will become crucial to ensure that the selection of targets is matched carefully against the availability and capability of follow-up telescopes. We propose a metric-based target selection approach that relies only on primary transit observables. The metric can be easily deployed within a distributed heterogeneous network of telescopes equipped to undertake either broadband photometry or spectroscopy. We show how the metric can be used either to optimise the observing strategy for a given telescope (e.g. choice of filter) or to enable the selection of the best telescope to optimise the overall sample size. The metric can also provide the basis for a selection function to help evaluate the statistical completeness of follow-up transmission spectroscopy datasets. Finally, we validate our metric by comparing its ranked set of targets against planets which have had their atmospheres successfully probed. We also compare the target list selected by our metric against some existing prioritised exoplanet lists.
I C F Mullerwodarg - One of the best experts on this subject based on the ideXlab platform.
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on the global distribution of neutral gases in titan s upper atmosphere and its effect on the thermal structure
Journal of Geophysical Research, 2003Co-Authors: I C F Mullerwodarg, R V Yelle, Michael Mendillo, A D AylwardAbstract:[1] Using a time-dependent general circulation model of Titan’s thermosphere, we calculate the global distribution of neutral gases by winds and diffusion. Our calculations suggest that solar driven dynamics effectively redistribute constituents, causing considerable diurnal and seasonal changes in gas abundances. Subsidence causes an accumulation of lighter gases on the nightside, with nighttime CH4 mole fractions at equinox near 1400 km reaching up to 50%. The reverse happens on the dayside, where lighter gases are depleted, giving minimum CH4 mole fractions near 1400 km of around 12%. The vertical transport time scales are around 5–10% of a Titan day, so these extrema in gas abundances are shifted with respect to local noon and midnight by up to 4 hours Local Solar Time (LST). The strong horizontal variations in gas abundances, combined with the local time shifts of their extrema, have an important impact on the thermal structure and lead to a shift of the nighttime minimum from local midnight towards early morning hours (0330 LST). This coupling between gas distribution and thermal structure on the nightside occurs via dynamical processes, primarily through changes in adiabatic heating. The redistribution of gases effectively controls, through changes in mean molecular weight, the pressure gradients, which in turn control the horizontal and vertical winds, and thereby adiabatic heating and cooling. On the dayside, changes in solar EUV absorption due to the redistributed gases occur but are comparatively small. Although it is possible with our calculations to identify important processes, Voyager and ground based observations of Titan are currently not sufficient to constrain the dynamics of Titan’s upper atmosphere, but comparisons with forthcoming Cassini observations are highly anticipated. INDEX TERMS: 6005 Planetology: Comets and Small Bodies: Atmospheres—composition and chemistry; 0355 Atmospheric Composition and Structure: Thermosphere—composition and chemistry; 3210 Mathematical Geophysics: Modeling; 6007 Planetology: Comets and Small Bodies: Atmospheres—structure and dynamics; 6025 Planetology: Comets and Small Bodies: Interactions with solar wind plasma and fields;
Sara Seager - One of the best experts on this subject based on the ideXlab platform.
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Comparative Planetology and the Search for Life Beyond the Solar System
arXiv: Astrophysics, 2006Co-Authors: Charles A. Beichman, Malcolm Fridlund, Wesley A. Traub, Karl R. Stapelfeldt, Andreas Quirrenbach, Sara SeagerAbstract:The study of planets beyond the solar system and the search for other habitable planets and life is just beginning. Ground-based (radial velocity and transits) and space-based surveys (transits and astrometry) will identify planets spanning a wide range of size and orbital location, from Earth-sized objects within 1 AU to giant planets beyond 5 AU, orbiting stars as near as a few parsec and as far as a kiloparsec. After this initial reconnaissance, the next generation of space observatories will directly detect photons from planets in the habitable zones of nearby stars. The synergistic combination of measurements of mass from astrometry and radial velocity, of radius and composition from transits, and the wealth of information from the direct detection of visible and mid-IR photons will create a rich field of comparative Planetology. Information on proto-planetary and debris disks will complete our understanding of the evolution of habitable environments from the earliest stages of planet-formation through to the transport into the inner solar system of the volatiles necessary for life. The suite of missions necessary to carry out the search for nearby, habitable planets and life requires a ``Great Observatories'' program for planet finding (SIM PlanetQuest, Terrestrial Planet Finder-Coronagraph, and Terrestrial Planet Finder-Interferometer/Darwin), analogous to the highly successful ``Great Observatories Program'' for astrophysics. With these new Great Observatories, plus the James Webb Space Telescope, we will extend Planetology far beyond the solar system, and possibly even begin the new field of comparative evolutionary biology with the discovery of life itself in different astronomical settings.
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on the dayside thermal emission of hot jupiters
The Astrophysical Journal, 2005Co-Authors: Sara Seager, L J Richardson, Brad M S Hansen, Kristen Menou, Drake DemingAbstract:We discuss atmosphere models of HD 209458b in light of the recent dayside flux measurement of HD 209458b's secondary eclipse by Spitzer MIPS at 24 μm. In addition, we present a revised secondary eclipse IRTF upper limit at 2.2 μm that places a stringent constraint on the adjacent H2O absorption band depths. These two measurements are complementary because they are both shaped by H2O absorption and because the former is on the Wien tail of the planet's thermal emission spectrum and the latter is near the thermal emission peak. A wide range of models fit the observational data, confirming our basic understanding of hot Jupiter atmospheric physics. Although a range of models are viable, some models at the hot and cold end of the plausible temperature range can be ruled out. One class of previously unconsidered hot Jupiter atmospheric models that fit the data are those with C/O 1 (as Jupiter may have), which have a significant paucity of H2O compared to solar abundance models with C/O = 0.5. The models indicate that HD 209458b is in a situation intermediate between pure in situ reradiation and very efficient redistribution of heat, one that will require a careful treatment of atmospheric circulation. We discuss how future wavelength- and phase-dependent observations will further constrain the atmospheric circulation regime. In the shorter term, additional planned measurements for HD 209458b, especially Spitzer IRAC photometry, should lift many of the model degeneracies. Multiwavelength IR observations constrain the atmospheric structure and circulation properties of hot Jupiters and thus open a new chapter in quantitative extrasolar Planetology.
J S Morgan - One of the best experts on this subject based on the ideXlab platform.
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exoplanetary atmosphere target selection in the era of comparative Planetology
Monthly Notices of the Royal Astronomical Society, 2019Co-Authors: J S Morgan, E Kerins, S Awiphan, Iain Mcdonald, J J Hayes, S Komonjinda, D Mkritchian, Nuanwan SanguansakAbstract:Large-scale transit surveys such as NGTS, TESS and PLATO promise to deliver a wealth of potential targets for follow-up transmission spectroscopy study. This will usher in an era of comparative Planetology that will be limited not by a paucity of targets but by the scarcity of follow-up assets on the ground and in space. It will become crucial to ensure that the selection of targets is matched carefully against the availability and capability of follow-up telescopes. We propose a metric-based target selection approach that relies only on primary transit observables. The metric can be easily deployed within a distributed heterogeneous network of telescopes equipped to undertake either broadband photometry or spectroscopy. We show how the metric can be used either to optimise the observing strategy for a given telescope (e.g. choice of filter) or to enable the selection of the best telescope to optimise the overall sample size. The metric can also provide the basis for a selection function to help evaluate the statistical completeness of follow-up transmission spectroscopy datasets. Finally, we validate our metric by comparing its ranked set of targets against planets which have had their atmospheres successfully probed. We also compare the target list selected by our metric against some existing prioritised exoplanet lists.
Eric Pilger - One of the best experts on this subject based on the ideXlab platform.
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modvolc near real time thermal monitoring of global volcanism
Journal of Volcanology and Geothermal Research, 2004Co-Authors: Robert Wright, Luke P Flynn, Harold Garbeil, Andrew J. L. Harris, Eric PilgerAbstract:MODVOLC is a non-interactive algorithm developed at the Hawaii Institute of Geophysics and Planetology (HIGP) that uses low spatial resolution (1-km pixel-size) infrared satellite data acquired by the Moderate Resolution Imaging Spectroradiometer (MODIS) to map the global distribution of volcanic thermal anomalies in near-real-time. MODVOLC scans the Level-1B MODIS data stream, on a pixel-by-pixel basis, for evidence of pixel and sub-pixel-sized high-temperature radiators. Once a hot spot has been identified its details (location, emitted spectral radiance, time, satellite observation geometry) are written to ASCII text files and transferred via FTP to HIGP, from where the results are disseminated via the internet http://modis.higp.hawaii.edu). In this paper, we review the underlying principles upon which the algorithm is based before presenting some of the results and data that have been obtained since its inception. We show how MODVOLC reliably detects thermal anomalies at a large number of persistently and sporadically active volcanoes that encompass the full range of common eruptive styles including Erebus (Antarctica), Colima (Mexico), Karymsky (Kamchatka), Popocatepetl (Mexico), Etna (Italy), and Nyiragongo (Democratic Republic of Congo), amongst others. We also present a few cautionary notes regarding the limitations of the algorithm and interpretation of the data it provides.
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automated volcanic eruption detection using modis
Remote Sensing of Environment, 2002Co-Authors: Robert Wright, Luke P Flynn, Harold Garbeil, Andrew J. L. Harris, Eric PilgerAbstract:Abstract The moderate resolution imaging spectroradiometer (MODIS) flown on-board NASA's first earth observing system (EOS) platform, Terra, offers complete global data coverage every 1–2 days at spatial resolutions of 250, 500, and 1000 m. Its ability to detect emitted radiation in the short (4 μm)- and long (12 μm)-wave infrared regions of the electromagnetic spectrum, combined with the excellent geolocation of the image pixels (∼200 m), makes it an ideal source of data for automatically detecting and monitoring high-temperature volcanic thermal anomalies. This paper describes the underlying principles of, and results obtained from, just such a system. Our algorithm interrogates the MODIS Level 1B data stream for evidence of high-temperature volcanic features. Once a hotspot has been identified, its details (location, emitted spectral radiance, satellite observational parameters) are written to an ASCII text file and transferred via file transfer protocol (FTP) to the Hawaii Institute of Geophysics and Planetology (HIGP), where the results are posted on the Internet ( http://modis.higp.hawaii.edu ). The global distribution of volcanic hotspots can be examined visually at a variety of scales using this website, which also allows easy access to the quantitative data contained in the ASCII files themselves. We outline how the algorithm has proven robust as a hotspot detection tool for a wide range of eruptive styles at both permanently and sporadically active volcanoes including Soufriere Hills (Montserrat), Popocatepetl (Mexico), Bezymianny (Russia), and Merapi (Java), amongst others. We also present case studies of how the system has allowed the onset, development, and cessation of discrete eruptive events to be monitored at Nyamuragira (Congo), Piton de la Fournaise (Reunion Island), and Shiveluch (Russia).