Galactic habitable zone around M and FGK stars with chemical evolution models that include dust

Abstract

Context. The Galactic habitable zone is defined as the region with highly enough metallicity to form planetary systems in which Earth-like planets could be born and might be capable of sustaining life surviving to the destructive effects of nearby supernova explosion events. Aims. Galactic chemical evolution models can be useful tools for studying the galactic habitable zones in different systems. Our aim here is to find the Galactic habitable zone using chemical evolution models for the Milky Way disc, adopting the most recent prescriptions for the evolution of dust and for the probability of finding planetary systems around M and FGK stars. Moreover, for the first time, we will express those probabilities in terms of the dust-to-gas ratio of the ISM in the solar neighborhood as computed by detailed chemical evolution models. Methods. At a fixed Galactic time and Galactocentric distance we determine the number of M and FGK stars having Earths (but no gas giant planets) which survived supernova explosions, using the formalism of our Paper I. Results. The probabilities of finding terrestrial planets but not gas giant planets around M stars deviate substantially from the ones around FGK stars for supersolar values of [Fe/H]. For both FGK and M stars the maximum number of stars hosting habitable planets is at 8 kpc from the Galactic Centre, if destructive effects by supernova explosions are taken into account. At the present time the total number of M stars with habitable planets are ≃ 10 times the number of FGK stars. Moreover, we provide a sixth order polynomial fit (and a linear one but more approximated) for the relation found with chemical evolution models in the solar neighborhood between the [Fe/H] abundances and the dust-to-gas ratio. Conclusions. The most likely Galactic zone to find terrestrial habitable planets around M and FGK stars is the annular region 2 kpc wide centred at 8 kpc from the Galactic center (the solar neighborhood). We also provide the probabilities of finding Earth-like planets as the function of the ISM dust-to-gas ratio using detailed chemical evolution models results.

The cosmic dust rate across the Universe

“…In this work, we use the same method adopted by Grieco et al (2014) but with noticeable improvements: first, we constrain our reference model of irregular, spiral and elliptical galaxies by the comparison with the observed dust amount in each galaxy type; second, we use a chemical evolution model with updated and detailed dust prescriptions, presented by Gioannini et al (2017) and recently adopted for the Milky Way in Spitoni et al (2017); third, we explore more evolutionary scenarios of galaxy formation than in Grieco et al (2014). Furthermore, since the dust content in galaxies is associated to star formation and to the presence of metals in the ISM, we compute also the cosmic metallicity evolution as well as the cosmic star formation rate (CSFR).…”

Galactic habitability re-examined: indications of bimodality

“…For an exception to this trend and somewhat prescient study which traces some of the ideas of the present work, see Suthar and McKay (2012). With the metallicity buildup being of crucial importance to build exoplanets, some of the more recent studies put emphasis on chemical evolution (Prantzos, 2008;Carigi et al, 2013;Spitoni et al, 2014Spitoni et al, , 2017, with some of them investigating the habitability of M31 (Carigi et al, 2013;Spitoni et al, 2014).…”

A Galactic centre gravitational-wave Messenger

“…We argue that if a sophisticated extraterrestrial civilisation would decide to construct a device to study the massive black hole in the Galactic centre, or to extract energy from it, or even for intentions unfathomable to the human mind, this device can, like Voyager 1 and 2 also serve as a Messenger. Any intentional gravitational-wave Messenger must be long lived and of an appropriate mass and density to produce a measurable signal in the least inhospitable parts of the Galaxy, about 6-10 kpc from the centre 25 . This means, it cannot be an arbitrary object on a "natural" orbit around a black hole, as the orbit would decay due to gravitational-wave emission and the Messenger-Sgr A * binary would merge.…”