Formulation and resolutions of the red sky paradox

Most stars in the Universe are red dwarfs. They outnumber stars like our Sun by a factor of 5 and outlive them by another factor of 20 (population-weighted mean). When combined with recent observations uncovering an abundance of temperate, rocky planets around these diminutive stars, we are faced with an apparent logical contradiction—Why do we not see a red dwarf in our sky? To address this “red sky paradox,” we formulate a Bayesian probability function concerning the odds of finding oneself around an F/G/K-spectral type (Sun-like) star. If the development of intelligent life from prebiotic chemistry is a universally rapid and ensured process, the temporal advantage of red dwarfs dissolves, softening the red sky paradox, but exacerbating the classic Fermi paradox. Otherwise, we find that humanity appears to be a 1-in-100 outlier. While this could be random chance (resolution I), we outline three other nonmutually exclusive resolutions (II to IV) that broadly act as filters to attenuate the suitability of red dwarfs for complex life. Future observations may be able to provide support for some of these. Notably, if surveys reveal a paucity of temperate rocky planets around the smallest (and most numerous) red dwarfs, then this would support resolution II. As another example, if future characterization efforts were to find that red dwarf worlds have limited windows for complex life due to stellar evolution, this would support resolution III. Solving this paradox would reveal guidance for the targeting of future remote life sensing experiments and the limits of life in the cosmos.

Physical variability of the magnetic field of some stars

The magnetic behavior of red dwarfs shows a change in physical magnetic field parameters in time periods of months-years. We investigate whether a similar variability is possible in stars of other types.

Characterizing the possible interior structures of the nearby Exoplanets Proxima Centauri b and Ross-128 b

ABSTRACT We developed a new numerical model to constrain the interior structure of rocky Exoplanets, and applied it to the nearby planets Proxima Centauri b and Ross-128 b. The recently measured elemental abundances of red dwarfs and Alpha Centauri were utilized to infer the bulk composition of each planet, and to measure their core mass fractions (CMFs). The results of our model predicted that the radius of Proxima b at its minimum mass may be 1.036 ± 0.040 R⊕, and if its mass is as high as 2 M⊕, 1.170 ± 0.040 R⊕. The radius of Ross-128 b at minimum mass may be 1.034 ± 0.040 R⊕, with its radius at an upper bound mass of 2 M⊕ being 1.150 ± 0.040 R⊕. Both planets may have thin mantles with similar conditions to Earth, but not convecting as vigorously. The CMFs might lie in the ranges of 20–59 per cent and 34–59 per cent for Proxima b and Ross-128 b, respectively, making it very likely they have massive iron cores. Their central temperatures may be high enough to partially melt the cores, and possibly generate magnetic fields. If they have magnetic fields at present, they are most likely to be multipolar in nature due to slow rotation speeds resulting from stellar tidal effects. The field strengths were predicted to have values of 0.06–0.23 G for Proxima b, and 0.07–0.14 G for Ross-128 b. If either planet contains more than 10 per cent of their mass in volatiles, magnetic fields would either be non-existent or very weak. The conditions of both planets may be hostile for habitability.

Stars from the GTSh10 catalogue in the Shajn's Plan

We examine objects from the GTSh10 catalogue among the studied stars as a part of implementing the Plan of Academician G.A. Shajn in order to replenish the database of photometric and spectral observations of red dwarfs. We consider a question concerning the cross-identification of data from the GTSh10 interactive version and the Shajn's Plan catalogues, as well as an access to the archive of photographic observations. The article is illustrated with examples of working with the obtained list by means of the Virtual Observatory in order to analyze the state of objects and/or to refine their photometric and spectral characteristics in the middle of the past century.