GJ 832c: A SUPER-EARTH IN THE HABITABLE ZONE

Evolution of novel activation functions in neural network training for astronomy data: habitability classification of exoplanets

Quantification of habitability is a complex task. Previous attempts at measuring habitability are well documented. Classification of exoplanets, on the other hand, is a different approach and depends on quality of training data available in habitable exoplanet catalogs. Classification is the task of predicting labels of newly discovered planets based on available class labels in the catalog. We present analytical exploration of novel activation functions as consequence of integration of several ideas leading to implementation and subsequent use in habitability classification of exoplanets. Neural networks, although a powerful engine in supervised methods, often require expensive tuning efforts for optimized performance. Habitability classes are hard to discriminate, especially when attributes used as hard markers of separation are removed from the data set. The solution is approached from the point of investigating analytical properties of the proposed activation functions. The theory of ordinary differential equations and fixed point are exploited to justify the "lack of tuning efforts" to achieve optimal performance compared to traditional activation functions. Additionally, the relationship between the proposed activation functions and the more popular ones is established through extensive analytical and empirical evidence. Finally, the activation functions have been implemented in plain vanilla feed-forward neural network to classify exoplanets. The mathematical exercise supplements the grand idea of classifying exoplanets, computing habitability scores/indices and automatic grouping of the exoplanets converging at some level.

Prediction of novel stable compounds in the Mg-Si-O system under exoplanet pressures

The Mg-Si-O system is the major Earth and rocky planet-forming system. Here, through quantum variable-composition evolutionary structure explorations, we have discovered several unexpected stable binary and ternary compounds in the Mg-Si-O system. Besides the well-known SiO₂ phases, we have found two extraordinary silicon oxides, SiO₃ and SiO, which become stable at pressures above 0.51 TPa and 1.89 TPa, respectively. In the Mg-O system, we have found one new compound, MgO₃, which becomes stable at 0.89 TPa. We find that not only the (MgO)_x·(SiO₂)_y compounds, but also two (MgO₃)_x·(SiO₃)_y compounds, MgSi₃O₁₂ and MgSiO₆, have stability fields above 2.41 TPa and 2.95 TPa, respectively. The highly oxidized MgSi₃O₁₂ can form in deep mantles of mega-Earths with masses above 20 M_⊕ (M_⊕:Earth’s mass). Furthermore, the dissociation pathways of pPv-MgSiO₃ are also clarified, and found to be different at low and high temperatures. The low-temperature pathway is MgSiO₃ ⇒ Mg₂SiO₄ + MgSi₂O₅ ⇒ SiO₂ + Mg₂SiO₄ ⇒ MgO + SiO₂, while the high-temperature pathway is MgSiO₃ ⇒ Mg₂SiO₄ + MgSi₂O₅ ⇒ MgO + MgSi₂O₅ ⇒ MgO + SiO₂. Present results are relevant for models of the internal structure of giant exoplanets, and for understanding the high-pressure behavior of materials.

Global warming as a detectable thermodynamic marker of Earth-like extrasolar civilizations: the case for a telescope like Colossus

Earth-like civilizations generate heat from the energy that they utilize. The thermal radiation from this heat can be a thermodynamic marker for civilizations. Here we model such planetary radiation on Earth-like planets and propose a strategy for detecting such an alien unintentional thermodynamic electromagnetic biomarker. We show that astronomical infrared (IR) civilization biomarkers may be detected within an interestingly large cosmic volume using a 70 m-class or larger telescope. In particular, the Colossus telescope with achievable coronagraphic and adaptive optics performance may reveal Earth-like civilizations from visible and IR photometry timeseries' taken during an exoplanetary orbit period. The detection of an alien heat signature will have far-ranging implications, but even a null result, given 70 m aperture sensitivity, could also have broad social implications.