4,229 research outputs found
Terrestrial Planet Formation Surrounding Close Binary Stars
Disk material has been observed around both components of some young close
binary star systems. It has been shown that if planets form at the right places
within such disks, they can remain dynamically stable for very long times.
Herein, we numerically simulate the late stages of terrestrial planet growth in
circumbinary disks around 'close' binary star systems with stellar separations
between 0.05 AU and 0.4 AU and binary eccentricities up to 0.8. In each
simulation, the sum of the masses of the two stars is 1 solar mass, and giant
planets are included. Our results are statistically compared to a set of planet
formation simulations in the Sun-Jupiter-Saturn system that begin with
essentially the same initial disk of protoplanets. The planetary systems formed
around binaries with apastron distances less than ~ 0.2 AU are very similar to
those around single stars, whereas those with larger maximum separations tend
to be sparcer, with fewer planets, especially interior to 1 AU. We also provide
formulae that can be used to scale results of planetary accretion simulations
to various systems with different total stellar mass, disk sizes, and
planetesimal masses and densities.Comment: 60 pages, 4 tables, and 11 low resolution eps figures. Article with
high resolution figures is available at
http://www-personal.umich.edu/~equintan/publications.html . Accepted for
publication in Icaru
Greenhouse Gas Inventory in the Forestry Sector
Among the components in the inventory of greenhouse gas sources and sinks, forestry and land use are the most complex. This paper summarizes the necessary data on land use. Analysis indicates a change in the inventory/sinks done by the Philippine Forestry and Land Use Change.land use planning, natural resources and environment, forestry sector, land management
Greenhouse Gas Inventory in the Forestry Sector
Among the components in the inventory of greenhouse gas sources and sinks, forestry and land use are the most complex. This paper summarizes the necessary data on land use. Analysis indicates a change in the inventory/sinks done by the Philippine Forestry and Land Use Change.land use planning, natural resources and environment, forestry sector, land management
A Revised Exoplanet Yield from the Transiting Exoplanet Survey Satellite (TESS)
The Transiting Exoplanet Survey Satellite (TESS) has a goal of detecting
small planets orbiting stars bright enough for mass determination via
ground-based radial velocity observations. Here we present estimates of how
many exoplanets the TESS mission will detect, physical properties of the
detected planets, and the properties of the stars that those planets orbit.
This work uses stars drawn from the TESS Input Catalog Candidate Target List
and revises yields from prior studies that were based on Galactic models. We
modeled the TESS observing strategy to select approximately 200,000 stars at
2-minute cadence, while the remaining stars are observed at 30-min cadence in
full-frame image data. We placed zero or more planets in orbit around each
star, with physical properties following measured exoplanet occurrence rates,
and used the TESS noise model to predict the derived properties of the detected
exoplanets. In the TESS 2-minute cadence mode we estimate that TESS will find
1250+/-70 exoplanets (90% confidence), including 250 smaller than 2
Earth-radii. Furthermore, we predict an additional 3100 planets will be found
in full-frame image data orbiting bright dwarf stars and more than 10,000
around fainter stars. We predict that TESS will find 500 planets orbiting
M-dwarfs, but the majority of planets will orbit stars larger than the Sun. Our
simulated sample of planets contains hundreds of small planets amenable to
radial velocity follow-up, potentially more than tripling the number of planets
smaller than 4 Earth-radii with mass measurements. This sample of simulated
planets is available for use in planning follow-up observations and analyses.Comment: Accepted for publication in ApJS. Table 2 is available in
machine-readable format from https://doi.org/10.6084/m9.figshare.613767
Climate Modeling of a Potential ExoVenus
The planetary mass and radius sensitivity of exoplanet discovery capabilities
has reached into the terrestrial regime. The focus of such investigations is to
search within the Habitable Zone where a modern Earth-like atmosphere may be a
viable comparison. However, the detection bias of the transit and radial
velocity methods lies close to the host star where the received flux at the
planet may push the atmosphere into a runaway greenhouse state. One such
exoplanet discovery, Kepler-1649b, receives a similar flux from its star as
modern Venus does from the Sun, and so was categorized as a possible exoVenus.
Here we discuss the planetary parameters of Kepler-1649b with relation to Venus
to establish its potential as a Venus analog. We utilize the general
circulation model ROCKE-3D to simulate the evolution of the surface temperature
of Kepler-1649b under various assumptions, including relative atmospheric
abundances. We show that in all our simulations the atmospheric model rapidly
diverges from temperate surface conditions towards a runaway greenhouse with
rapidly escalating surface temperatures. We calculate transmission spectra for
the evolved atmosphere and discuss these spectra within the context of the
James Webb Space Telescope (JWST) Near-Infrared Spectrograph (NIRSpec)
capabilities. We thus demonstrate the detectability of the key atmospheric
signatures of possible runaway greenhouse transition states and outline the
future prospects of characterizing potential Venus analogs.Comment: 11 pages, 4 figures, 1 table, accepted for publication in the
Astrophysical Journal. The data from this paper are open source and are
available from the following data portals:
https://portal.nccs.nasa.gov/GISS_modelE/ROCKE-3D/Climate_Modeling_of_a_Potential_ExoVenus
https://archive.org/details/Climate_Modeling_of_a_Potential_ExoVenu
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