Habitable Zones & Global Climate: January 2020

We analyzed the thermodynamics of hypothetical exoplanets at very low Keplerian circular orbits in close vicinity of rapidly spinning supermassive black holes.

Research supported in part by the NASA Astrobiology Program provides new insight into the 'faint young Sun problem.'

In the search for life beyond Earth, astronomers look for planets in a star's "habitable zone" -- sometimes nicknamed the "Goldilocks zone" -- where temperatures are just right for liquid water to exist on a planet's surface to nurture life as we know it.

A planet's climate can be strongly affected by its orbital eccentricity and obliquity. Here we use a 1-dimensional energy balance model modified to include a simple runaway greenhouse (RGH) parameterization to explore the effects of these two parameters on the climate of Earth-like aqua planets - completely ocean-covered planets - orbiting F-, G-, K-, and M-dwarf stars.

Although habitability, defined as the general possibility of hosting life, is expected to occur under a broad range of conditions, the standard scenario to allow for habitable environments is often described through habitable zones (HZs).

NASA's Transiting Exoplanet Survey Satellite (TESS) has discovered its first Earth-size planet in its star's habitable zone, the range of distances where conditions may be just right to allow the presence of liquid water on the surface.

Large ground- and space-based telescopes will be able to observe Earth-like planets in the near future. We explore how different planetary surfaces can strongly influence the climate, atmospheric composition, and remotely detectable spectra of terrestrial rocky exoplanets in the habitable zone depending on the host star's incident irradiation spectrum for a range of Sun-like host stars from F0V to K7V.

Tidally locked terrestrial planets around low-mass stars are the prime targets for future atmospheric characterizations of potentially habitable systems, especially the three nearby ones--Proxima b, TRAPPIST-1e, and LHS 1140b.