Many known exoplanets today are ‘super-Earths’, with a radius of 1.3 times that of Earth, and ‘mini-Neptunes’, with 2.4 Earth radii.
The mini-Neptunes, which are less dense, were long thought to be gaseous planets, composed of hydrogen and helium. Now, scientists from the Laboratoire d’Astrophysique de Marseille (CNRS / Aix-Marseille Université / Cnes)[1] They 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 of its host star.
These findings, recently published in The letters of the astrophysical journal, show that mini-Neptunes could be super-Earths with a rocky core surrounded by water in a supercritical state[2], suggesting that these two types of exoplanet it can be formed in the same way.
Another article recently published in Astronomy AND Astrophysics, involving scientists in France mainly from the CNRS and the University of Bordeaux[3], focused on the effect of stellar irradiation on the radius of Earth-sized planets that contain water. His work shows that the size of the atmospheres of such planets increases considerably when subjected to a strong greenhouse effect, according to the study on mini-Neptunes.
Future observations should make it possible to test these new hypotheses put forward by French scientists, who are making important contributions to our knowledge of exoplanets.
References
Bridge of irradiated oceanic planets Super-Earth and Sub-Neptune Populations ”by Olivier Mousis, Magali Deleuil, Artyom Aguichine, Emmanuel Marcq2, Joseph Naar, Lorena Acuña Aguirre, Bastien Brugger and Thomas Gonçalves, June 15, 2020, The letters of the astrophysical journal.
DOI: 10.3847 / 2041-8213 / ab9530
“Radio mass ratios for water-rich rocky planets more irradiated than the runaway greenhouse boundary” were reviewed by Turbet, Martin; Bolmont Emeline; Ehrenreich, David; Gratier, Pierre; Leconte, Jérémy; Selsis, Franck; Hara, Nathan; Lovis, Christophe, June 9, 2020, Astronomy and astrophysics.
DOI: 10.1051 / 0004-6361 / 201937151
Notes
- In collaboration with a researcher at the Laboratoire Atmosphères et Observations Spatiales (CNRS / UVSQ / Sorbonne Université)
- Supercritical water exists at very high pressures and temperatures.
- French scientists work at the Laboratoire d’Astrophysique de Bordeaux (CNRS / Université de Bordeaux) and used a planetary atmosphere model developed at the Laboratoire de Météorologie Dynamique (CNRS / ENS Paris / Ecole Polytechnique – Institut Polytechnique de Paris / Sorbonne Université) .
