1,357 research outputs found
The Exoplanet Population Observation Simulator. II -- Population Synthesis in the Era of Kepler
The collection of planetary system properties derived from large surveys such
as Kepler provides critical constraints on planet formation and evolution.
These constraints can only be applied to planet formation models, however, if
the observational biases and selection effects are properly accounted for. Here
we show how epos, the Exoplanet Population Observation Simulator, can be used
to constrain planet formation models by comparing the Bern planet population
synthesis models to the Kepler exoplanetary systems. We compile a series of
diagnostics, based on occurrence rates of different classes of planets and the
architectures of multi-planet systems, that can be used as benchmarks for
future and current modeling efforts. Overall, we find that a model with 100
seed planetary cores per protoplanetary disk provides a reasonable match to
most diagnostics. Based on these diagnostics we identify physical properties
and processes that would result in the Bern model more closely matching the
known planetary systems. These are: moving the planet trap at the inner disk
edge outward; increasing the formation efficiency of mini-Neptunes; and
reducing the fraction of stars that form observable planets. We conclude with
an outlook on the composition of planets in the habitable zone, and highlight
that the majority of simulated planets smaller than 1.7 Earth radii have
substantial hydrogen atmospheres.
The software used in this paper is available online for public scrutiny at
https://github.com/GijsMulders/eposComment: Accepted in Ap
Highlights from the Pierre Auger Observatory
The Pierre Auger Observatory is the world's largest cosmic ray observatory.
Our current exposure reaches nearly 40,000 km str and provides us with an
unprecedented quality data set. The performance and stability of the detectors
and their enhancements are described. Data analyses have led to a number of
major breakthroughs. Among these we discuss the energy spectrum and the
searches for large-scale anisotropies. We present analyses of our X
data and show how it can be interpreted in terms of mass composition. We also
describe some new analyses that extract mass sensitive parameters from the 100%
duty cycle SD data. A coherent interpretation of all these recent results opens
new directions. The consequences regarding the cosmic ray composition and the
properties of UHECR sources are briefly discussed.Comment: 9 pages, 12 figures, talk given at the 33rd International Cosmic Ray
Conference, Rio de Janeiro 201
Earths in Other Solar Systems N-body simulations: the Role of Orbital Damping in Reproducing the Kepler Planetary Systems
The population of exoplanetary systems detected by Kepler provides
opportunities to refine our understanding of planet formation. Unraveling the
conditions needed to produce the observed exoplanets will sallow us to make
informed predictions as to where habitable worlds exist within the galaxy. In
this paper, we examine using N-body simulations how the properties of planetary
systems are determined during the final stages of assembly. While accretion is
a chaotic process, trends in the ensemble properties of planetary systems
provide a memory of the initial distribution of solid mass around a star prior
to accretion. We also use EPOS, the Exoplanet Population Observation Simulator,
to account for detection biases and show that different accretion scenarios can
be distinguished from observations of the Kepler systems. We show that the
period of the innermost planet, the ratio of orbital periods of adjacent
planets, and masses of the planets are determined by the total mass and radial
distribution of embryos and planetesimals at the beginning of accretion. In
general, some amount of orbital damping, either via planetesimals or gas,
during accretion is needed to match the whole population of exoplanets.
Surprisingly, all simulated planetary systems have planets that are similar in
size, showing that the "peas in a pod" pattern can be consistent with both a
giant impact scenario and a planet migration scenario. The inclusion of
material at distances larger than what Kepler observes has a profound impact on
the observed planetary architectures, and thus on the formation and delivery of
volatiles to possible habitable worlds.Comment: Resubmitted to ApJ. Planet formation models available online at
http://eos-nexus.org/genesis-database
The Exoplanet Population Observation Simulator. I - The Inner Edges of Planetary Systems
The Kepler survey provides a statistical census of planetary systems out to
the habitable zone. Because most planets are non-transiting, orbital
architectures are best estimated using simulated observations of ensemble
populations. Here, we introduce EPOS, the Exoplanet Population Observation
Simulator, to estimate the prevalence and orbital architectures of multi-planet
systems based on the latest Kepler data release, DR25. We estimate that at
least 42% of sun-like stars have nearly coplanar planetary systems with 7 or
more exoplanets. The fraction of stars with at least one planet within 1 au
could be as high as 100% depending on assumptions about the distribution of
single transiting planets. We estimate an occurrence rate of planets in the
habitable zone around sun-like stars of eta_earth=36+-14%. The innermost
planets in multi-planet systems are clustered around an orbital period of 10
days (0.1 au), reminiscent of the protoplanetary disk inner edge or could be
explained by a planet trap at that location. Only a small fraction of planetary
systems have the innermost planet at long orbital periods, with fewer than ~8%
and ~3% having no planet interior to the orbit of Mercury and Venus,
respectively. These results reinforce the view that the solar system is not a
typical planetary system, but an outlier among the distribution of known
exoplanetary systems. We predict that at least half of the habitable zone
exoplanets are accompanied by (non-transiting) planets at shorter orbital
periods, hence knowledge of a close-in exoplanet could be used as a way to
optimize the search for Earth-size planets in the Habitable Zone with future
direct imaging missions.Comment: Accepted in AAS journals, code available on githu
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