National Center for Scientific Research, France | 2020 Jul 20
Many exoplanets known today are ‘super-Earths,’ with a radius 1.3 times that of Earth, and ‘mini-Neptunes,’ with 2.4 Earth radii. Mini-Neptunes, which are less dense, were long thought to be gas planets, made up of hydrogen and helium. Now, scientists ... have examined a new possibility, namely that the low density of mini-Neptunes could be explained simply by the presence of a thick layer of water that experiences an intense greenhouse effect caused by the irradiation from their host star.Water World: Depiction of a Planet Completely Covered with Ocean
Credit: NASA Kepler Mission/Dana Berry
These findings ... show that mini-Neptunes could be super-Earths with a rocky core surrounded by water in a supercritical state, suggesting that these two types of exoplanet may form in the same way.
Another paper ... focused on the effect of stellar irradiation on the radius of Earth-sized planets containing water. Their work shows that the size of the atmospheres of such planets increases considerably when subject to a strong greenhouse effect, in line with the study on mini-Neptunes.
Future observations should make it possible to test these novel hypotheses put forward by French scientists, who are making major contributions to our knowledge of exoplanets.
Irradiated Ocean Planets Bridge Super-Earth and Sub-Neptune Populations ~ Olivier Mousis et al
- Astrophysical Journal Letters 896(2):L22 (2020 Jun 20) DOI: 10.3847/2041-8213/ab9530
- arXiv.org > astro-ph > arXiv:2002.05243 > 12 Feb 2020 (v1), 26 May 2020 (v2)
More Irradiated Than the Runaway Greenhouse Limit ~ Martin Turbet et al