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PostPosted: Tue May 23, 2017 1:42 pm 
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Posts: 191
Neutron Star Planets: Atmospheric processes and habitability

The Drake Equation as a Function of Spectral Type and Time

"We suggest that the maximum lifetime of communicative civilizations depends on the spectral type of the host star, which implies that F- and G-dwarf stars are the best places to search for signs of technological intelligence today."

Why do we find ourselves around a yellow star instead of a red star?

"In this paper we analyze this problem through Bayesian inference to demonstrate that our occurrence around a G-dwarf might be a slight statistical anomaly, but only the sort of chance event that we expect to occur regularly."


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PostPosted: Fri May 26, 2017 1:25 pm 
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Posts: 191
No snowball on habitable tidally locked planets

"We show that tidally locked planets are unlikely to exhibit a snowball bifurcation as a direct result of the spatial pattern of insolation they receive. Instead they will smoothly transition from partial to complete ice coverage and back. A major implication of this work is that tidally locked planets with an active carbon cycle should not be found in a snowball state. Moreover, this work implies that tidally locked planets near the outer edge of the habitable zone with low CO2 outgassing fluxes will equilibrate with a small unglaciated substellar region rather than cycling between warm and snowball states."


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PostPosted: Tue May 30, 2017 12:30 pm 
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On the Spin States of Habitable Zone Exoplanets Around M Dwarfs: The Effect of a Near-Resonant Companion

"...we find that a planetary companion near a mean-motion resonance can excite the spin states of planets in the habitable zone of small, cool stars, pushing otherwise synchronously rotating planets into higher amplitude librations of the spin state, or even complete circulation resulting in effective stellar days with full surface coverage on the order of years or decades."


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PostPosted: Tue Jun 13, 2017 12:59 pm 
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Posts: 191
Constraining the Compositions of the TRAPPIST-1 Planets to Trace Snow Lines and Migration in M Dwarf Disks

On the Age of the TRAPPIST-1 System

"...conclude that TRAPPIST-1 is a transitional thin/thick disk star with an age of 7.6±2.2 Gyr."


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PostPosted: Thu Jun 22, 2017 1:33 pm 
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Posts: 191
The Detectability of Radio Auroral Emission from Proxima B

Comparative Climates of TRAPPIST-1 planetary system: results from a simple climate-vegetation model

"...TRAPPIST-1d seems to be the most stable from an Earth-like perspective, since it resides in the surface water zone for a wide range of reasonable values of the model parameters. Moreover, according to the model outer planets (f, g and h) cannot host liquid water on their surfaces, even for Earth-like conditions, entering a snowball state."

Stable habitable zones of single Jovian planet systems

"We find that small, Earth-mass planets can maintain stable orbits in cases where the habitable zone is largely, or partially, unperturbed by a nearby Jovian, and that mutual gravitational interactions and resonant mechanisms are capable of producing stable orbits even in habitable zones that are significantly or completely disrupted by a Jovian."


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PostPosted: Tue Jul 18, 2017 1:00 pm 
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Physical constraints on the likelihood of life on exoplanets

"From our analysis, we demonstrate that Earth-sized exoplanets in the habitable zone around M-dwarfs seemingly display much lower prospects of being habitable relative to Earth, owing to the higher incident ultraviolet fluxes and closer distances to the host star. We illustrate our results by specifically computing the likelihood (of supporting life) for the recently discovered exoplanets, Proxima b and TRAPPIST-1e, which we find to be several orders of magnitude smaller than that of Earth."


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PostPosted: Thu Jul 20, 2017 12:44 pm 
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The habitability of a stagnant-lid Earth

"Plate tectonics is a fundamental component for the habitability of the Earth. Yet whether it is a recurrent feature of terrestrial bodies orbiting other stars or unique to the Earth is unknown. The stagnant lid may rather be the most common tectonic expression on such bodies. ... At 1 au, the stagnant-lid planet considered would be regarded as habitable."


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PostPosted: Sun Jul 23, 2017 3:20 pm 
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The Equilibrium Temperature of Planets in Elliptical Orbits: https://arxiv.org/abs/1702.07314

http://phl.upr.edu/press-releases/coolorbit

"A common assumption in the search for habitable abodes beyond Earth is that the average temperature of planets always increases the more elliptical their orbit is. Now, scientists from the Planetary Habitability Laboratory (PHL) and the Arecibo Observatory in Puerto Rico have shown that planets in elliptical orbits are generally colder than previously believed."

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PostPosted: Wed Jul 26, 2017 2:32 pm 
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Reduced Diversity of Life Around Proxima Centauri and TRAPPIST-1

"...we arrive at two striking conclusions: (i) Earth-analogs orbiting low-mass M-dwarfs are unlikely to be inhabited, and (ii) K-dwarfs and some G-type stars are potentially capable of hosting more complex biospheres than the Earth."

Exomoon Habitability and Tidal Evolution in Low-Mass Star Systems

"We show that dwarf stars with masses ≲0.2 M⊙ cannot host habitable exomoons within the stellar HZ due to extreme tidal heating in the moon. Perturbations from a central star may continue to have deleterious effects in the HZ up to ≈0.5 M⊙, depending on the host planet's mass and its location in the HZ, amongst others."


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PostPosted: Fri Jul 28, 2017 12:10 am 
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On the Dearth of Galilean Analogs in Kepler and the Exomoon Candidate Kepler-1625b I

"We find that the occurrence rate of Galilean-analog moon systems can be constrained to be η<0.38 to 95% confidence for the 284 KOIs considered, with a 68.3% confidence interval of η=0.16 (-0.10 to +0.13). A single-moon model of variable size and separation locates a slight preference for a population of super-Ios, ~0.5 R_Earth moons orbiting at 5-10 planetary radii. However, we stress that the low Bayes factor of just 2 in this region means it should be treated as no more than a hint at this time."

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