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There are two dominant and contrasting classes of origin of life scenarios: those predicting that life emerged in submarine hydrothermal systems, where chemical disequilibrium can provide an energy source for nascent life; and those…
There is some experimental evidence that some stars are older than the Universe in General Relativity based cosmology. In TGD based cosmology the paradox has explanation. Photons can be either topologically condensed on background spacetime…
During the epoch of reionization, the formation of radiation sources is accompanied by the growth of a H- photodissociating flux. We estimate the impact of this flux on the formation of molecular hydrogen and cooling in the first galaxies,…
[Abridged] Most exoplanets detected so far are close-in planets, which are likely to be affected by tidal dissipation in their host star. To get a complete picture of the evolution of star-planet systems one needs to consider the impact of…
We discuss implications of a stellar-dominated UV background at high redshifts. The composite spectrum of 29 LBGs evaluated by Steidel etal (2000) at <z>=3.4 can be well fit by a stellar population with ongoing star formation, a Salpeter…
It is shown that several habitability conditions (in fact, at least seven such conditions) appear to be fulfilled automatically by circumbinary planets of main-sequence stars (CBP-MS), whereas on Earth these conditions are fulfilled only by…
The search for life elsewhere in the universe is a pivotal question in modern science. However, to address whether life is common in the universe we must first understand the likelihood of abiogenesis by studying the origin of life on…
The detections of atomic hydrogen, heavy atoms and ions surrounding the extrasolar giant planet (EGP) HD209458b constrain the composition, temperature and density profiles in its upper atmosphere. Thus the observations provide guidance for…
The question "What is life?" has been asked and studied by the researchers of various fields. Nevertheless, no global theory which unified various aspects of life has been proposed so far. Considering that the physical principle for the…
Life has most likely originated as a consequence of processes taking place in non-equilibrium conditions (\textit{e.g.} in the proximity of deep-sea thermal vents) selecting states of matter that would have been otherwise unfavorable at…
Planet Earth has evolved from an entirely anoxic planet with possibly a different tectonic regime to the oxygenated world with horizontal plate tectonics that we know today. For most of this time, Earth has been inhabited by a purely…
The galactic habitable zone is defined as the region with sufficient abundance of heavy elements to form planetary systems in which Earth-like planets could be born and might be capable of sustaining life, after surviving to close supernova…
People usually smile when astrophysicists assert that we are sons of the stars, but human life confirms this sentence: about 65% of the mass of our body is made up of oxygen, carbon occurs in all organic life and is the basis of organic…
The hydrogen-deficiency in extremely hot post-AGB stars of spectral class PG1159 is probably caused by a (very) late helium-shell flash or a AGB final thermal pulse that consumes the hydrogen envelope, exposing the usually-hidden intershell…
We generalize the problem of the semi-gray model to cases in which a non-negligible fraction of the stellar radiation falls on the long-wavelength range, and/or that the planetary long-wavelength emission penetrates into the transparent…
We present models of the late stages of stellar evolution intended to explain the UV upturn phenomenon in elliptical galaxies. Such models are sensitive to values of a number of poorly-constrained physical parameters, including metallicity,…
Atmospheric escape from close-in Neptunes and hot Jupiters around sun-like stars driven by extreme ultraviolet (EUV) irradiation plays an important role in the evolution of exo-planets and in shaping their ensemble properties. Intermediate…
We carry out 3-D numerical simulations to assess the penetration and bombardment effects of Solar Energetic Particles (SEPs), i.e. high-energy particle bursts during large flares and superflares, on ancient and current Mars. We demonstrate…
We present a determination of photospheric parameters and C abundances for a sample of 172 G and K dwarfs, subgiants, and giants with and without detected planets in the solar neighbourhood. The analysis was based on high S/N and high…
The availability of bioessential elements for "life as we know it", such as phosphorus (P) or possibly molybdenum (Mo), is expected to restrict the biological productivity of extraterrestrial biospheres. Here, we consider worlds with…