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PostPosted: Thu Mar 29, 2018 2:34 pm 
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A brief overview of planet formation

"I provide an overview of the current status of planet formation theory, and discuss how it connects to observations.

Comments: Short introduction, aimed at new students, for a forthcoming survey volume"


Stable equatorial ice belts at high obliquity in a coupled ocean-atmosphere model

"Three stable climate states are obtained that differ in the extent of the sea ice cover. For low values of irradiation the model simulates a Cryoplanet which has a perennial global sea ice cover. By increasing stellar irradiance, transitions occur to an Uncapped Cryoplanet with a perennial equatorial sea ice belt, and eventually to an Aquaplanet with no ice. ... Our results show that perennial equatorial ice cover is a viable climate state of a high-obliquity exoplanet, but a vigorous ocean circulation may render it unstable."


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PostPosted: Fri Apr 06, 2018 1:19 pm 
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Planetary population synthesis

Another chapter from the upcoming Exoplanets Handbook. Probably the most useful from a worldbuilding standpoint so far, as it goes into the statistical results of planetary system formation models.

"In this review of planetary population synthesis, we first briefly list key observational constraints. Then, the work flow in the method and its two main components are presented, namely global end-to-end models that predict planetary system properties directly from protoplanetary disk properties and probability distributions for these initial conditions. An overview of various population synthesis models in the literature is given. The sub-models for the physical processes considered in global models are described: the evolution of the protoplanetary disk, the planets' accretion of solids and gas, orbital migration, and N-body interactions among concurrently growing protoplanets. Next, typical population synthesis results are illustrated in the form of new syntheses obtained with the latest generation of the Bern model. Planetary formation tracks, the distribution of planets in the mass-distance and radius-distance plane, the planetary mass function, and the distributions of planetary radii, semimajor axes, and luminosities are shown, linked to underlying physical processes, and compared with their observational counterparts. We finish by highlighting the most important predictions made by population synthesis models and discuss the lessons learned from these predictions - both those later observationally confirmed and those rejected."


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PostPosted: Fri Apr 06, 2018 10:44 pm 
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thrash wrote:
Planetary population synthesis

Another chapter from the upcoming Exoplanets Handbook. Probably the most useful from a worldbuilding standpoint so far, as it goes into the statistical results of planetary system formation models.

Shiny!

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PostPosted: Mon Apr 09, 2018 12:59 pm 
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The First Naked-Eye Superflare Detected from Proxima Centauri

"In March 2016, the Evryscope observed the first naked-eye-visible superflare detected from Proxima Centauri. Proxima increased in brightness by a factor of ~68 during the superflare and released a bolometric energy of 10^33.5 erg, ~10X larger than any previously-detected flare from Proxima. Over the last two years the Evryscope has recorded 23 other large Proxima flares ranging in bolometric energy from 10^30.6 erg to 10^32.4 erg; coupling those rates with the single superflare detection, we predict at least five superflares occur each year. Simultaneous high-resolution HARPS spectroscopy during the Evryscope superflare constrains the superflare's UV spectrum and any associated coronal mass ejections. We use these results and the Evryscope flare rates to model the photochemical effects of NOx atmospheric species generated by particle events from this extreme stellar activity, and show that the repeated flaring is sufficient to reduce the ozone of an Earth-like atmosphere by 90% within five years. We estimate complete depletion occurs within several hundred kyr. The UV light produced by the Evryscope superflare therefore reached the surface with ~100X the intensity required to kill simple UV-hardy microorganisms, suggesting that life would struggle to survive in the areas of Proxima b exposed to these flares."


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PostPosted: Mon Apr 09, 2018 9:52 pm 
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Bad news for the "habitable planet" orbiting Proxima... :(

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PostPosted: Tue Apr 10, 2018 2:02 am 
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Life on a seabed should still be good though?

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PostPosted: Tue Apr 10, 2018 2:17 pm 
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Role of stellar physics in regulating the critical steps for life

"The critical step model suggests that the habitability of Earth-analogs around M-dwarfs is significantly suppressed. The total number of stars with planets containing detectable biosignatures of microbial life is expected to be highest for K-dwarfs. In contrast, we find that the corresponding value for intelligent life (technosignatures) should be highest for solar-mass stars."


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PostPosted: Thu Apr 12, 2018 1:43 pm 
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Connecting Planetary Composition with Formation

A review paper, more of a backgrounder than directly useful for worldbuilding.


The Silurian Hypothesis: Would it be possible to detect an industrial civilization in the geological record?

"We summarize the likely geological fingerprint of the Anthropocene, and demonstrate that while clear, it will not differ greatly in many respects from other known events in the geological record. We then propose tests that could plausibly distinguish an industrial cause from an otherwise naturally occurring climate event."

The paper lists a number of events in the current geological record with signatures comparable to our civilization. These might make good origins for Out of Place Artifacts or Things Man Was Not Meant To Know.


Interstellar Escape from Proxima b is Barely Possible with Chemical Rockets

More bad news for our nearest neighbors.


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PostPosted: Wed Apr 18, 2018 12:44 pm 
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Highly Volcanic Exoplanets, Lava Worlds, and Magma Ocean Worlds: An Emerging Class of Dynamic Exoplanets of Significant Scientific Priority

"Highly volcanic exoplanets, which can be variously characterized as 'lava worlds', 'magma ocean worlds', or 'super-Ios' are high priority targets for investigation. The term 'lava world' may refer to any planet with extensive surface lava lakes, while the term 'magma ocean world' refers to planets with global or hemispherical magma oceans at their surface. 'Highly volcanic planets', including super-Ios, may simply have large, or large numbers of, active explosive or extrusive volcanoes of any form."


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PostPosted: Sat May 05, 2018 7:54 pm 
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Planet Populations as a Function of Stellar Properties

"This chapter [in the Handbook of Exoplanets] describes the observed relations between exoplanet populations and stellar properties and how they connect to planet formation in protoplanetary disks."


TRAPPIST-1e Has a Large Iron Core

"... TRAPPIST-1e therefore possess [sic] a large iron core similar to the Earth, in addition to being Earth-sized and located in the temperature [sic] zone."


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