The Climate and Habitability of M-dwarf Planets
Aomawa Shields, University of California, Los Angeles/ Harvard University
M-dwarf stars comprise over 70% of all stars in the nearby solar neighborhood, so they offer the best chance of finding habitable planets through sheer numbers alone. They also demonstrate clear observational advantages, as smaller, Earth-sized planets are easier to detect around these small stars. Additionally, the long stellar lifetimes of M-dwarf stars would provide lengthy timescales for planetary and biological evolution.
However, the prospects for the habitability of planets orbiting M-dwarf stars have long been debated, due to key differences between the unique stellar and planetary environments around these low-mass stars, as compared to hotter, brighter stars. Specifically, the habitability of these short-period planets is complicated by the close proximity of the habitable zones of low-mass stars, given their lower stellar luminosities. In such close-in orbits, tidal effects between the star and the orbiting planet are strong, and could modify the rotation rate of the planet. This may have a significant impact on its climate and habitability.
Significant progress has been made by both space and ground-based observatories to better constrain the likelihood of small planets to orbit in the habitable zones of M-dwarf stars, and future planned missions will target nearby M-dwarfs in search of habitable planets, and attempt to characterize their atmospheres. Theoretical studies have also quantified the effect on climate and habitability of the interaction between the spectral energy distribution of M-dwarf stars and the atmosphere and surface of their planets, and explored the effect on climate of additional factors unique to M-dwarf planetary and stellar environments. In this presentation I will provide an overview of some of the most exciting research done on the subject of M-dwarf planet habitability, and summarize future observational and theoretical directions planned in this quickly evolving field.