Climate variations on Earth-like circumbinary planets

Abstract

The discovery of planets orbiting double stars at close distances has sparked increasing scientific interest in determining whether Earth-analogues can remain habitable in such environments and how their atmospheric dynamics is influenced by the rapidly changing insolation. In this work we present results of the first three-dimensional numerical experiments of a water-rich planet orbiting a double star. We find that the periodic forcing of the atmosphere has a noticeable impact on the planet's climate. Signatures of the forcing frequencies related to the planet's as well as to the binary's orbital periods are present in a variety of climate indicators such as temperature and precipitation, making the interpretation of potential observables challenging. However, for Earth-like greenhouse gas concentrations, the variable forcing does not change the range of insolation values allowing for habitable climates substantially.

Constraining the Magnitude of Climate Extremes From Time‐Varying Instellation on a Circumbinary Terrestrial Planet

“…Our model calculations support the results of Popp and Eggl (), showing small temperature variations from the gyration effect, when we examine a planet with global ocean coverage (Figures and , top row). But when we include Earth‐like land coverage or an equatorial supercontinent (Figures and , middle and bottom rows, respectively), we find that the lower effective heat capacity increases the extent of surface temperature variation.…”

“…This section examines the amplitude of temperature variation due to the time‐dependent circumbinary gyration effect. The analytic energy balance calculations shown below demonstrate that the effect typically causes temperature to oscillate by only a few degrees for most cases, which is consistent with previous results (May & Rauscher, ; Popp & Eggl, ). At the same time, planets with a much lower effective heat capacity may experience tens of degrees of temperature change.…”

“…The largest changes in temperature occur for planets with low effective heat capacity and a large amplitude of periodic forcing. Most of the parameter space shows only a few degrees total warming (and, analogously, the same amount of cooling), which corroborate previous studies (May & Rauscher, ; Popp & Eggl, ). This suggests that the gyration effect is unlikely to substantially undermine the habitability of an Earth‐like planet under the most typical conditions.…”

Stable Climates for Temperate Rocky Circumbinary Planets

“…As expected, temperature variations are muted over oceans, with a minimum in temperature variability occurring over the Pacific ocean. This finding is in line with the GCM simulations of Popp and Eggl (2017), who found small temperature changes in ocean-covered simulations of otherwise Earth-like circumbinary planets. However, temperature variations can be significant over land in the tropics and subtropics, for example, over Africa and South America.…”

On the Lack of Circumbinary Planets Orbiting Isolated Binary Stars

“…In recent years, numerous theoretical modeling efforts have sought to characterize how the presence of two stars impacts the potential habitability of CBPs (e.g. Kane & Hinkel 2013;Forgan 2014;Popp & Eggl 2017). As future studies look to characterize and detect potentially habitable CBPs, we suggest that such efforts should focus on longer-period binaries, those with P orb > ∼ 7.5 days, as in this regime, the STEEP process is less likely to result in the ejection of close-in CBPs.…”