Monday, October 10, 2016

The Universe Will Remain Habitable Until the Death of the Last Stars

The habitability of the Universe through 13 billion years of cosmic time


Dayal et al


The field of astrobiology has made tremendous progress in modelling galactic-scale habitable zones which offer a stable environment for life to form and evolve in complexity. Recently, this idea has been extended to cosmological scales by studies modelling the habitability of the local Universe in its entirety (e.g. Dayal et al. 2015; Li & Zhang 2015). However, all of these studies have solely focused on estimating the potentially detrimental effects of either Type II supernovae (SNII) or Gamma Ray Bursts (GRBs), ignoring the contributions from Type Ia supernovae (SNIa) and active galactic nuclei (AGN). In this study we follow two different approaches, based on (i) the amplitude of deleterious radiation and (ii) the total planet-hosting volume irradiated by deleterious radiation. We simultaneously track the contributions from the key astrophysical sources (SNII, SNIa, AGN and GRBs) for the entire Universe, for both scenarios, to determine its habitability through 13.8 billion years of cosmic time. We find that SNII dominate the total radiation budget and the volume irradiated by deleterious radiation at any cosmic epoch closely followed by SNIa (that contribute half as much as SNII), with GRBs and AGN making up a negligible portion (<1 1="" 2.5="" 20="" 3="" 4="" a="" affected="" after="" ago.="" and="" appeared="" as="" assumptions="" billion="" billions="" blockquote="" building-up="" compared="" cosmic="" deleterious="" density="" depending="" die="" earth="" exact="" falling-off="" final="" find="" first="" habitability="" habitable="" has="" hundreds="" in="" increase="" increased="" is="" life="" mass="" model="" more="" next="" number="" of="" on="" or="" out="" over="" persist="" planets="" radiation="" result="" secondly="" slowly="" stars="" steadily="" that="" the="" this="" through="" time.="" time="" times="" to="" today="" total="" universe="" until="" volume="" we="" when="" will="" with="" years.="" years="">

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