Mini-Neptunes Could Be Irradiated Ocean Planets

Mini Neptune

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Many exoplanets understood 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 thick, were long believed to be gas worlds, comprised of hydrogen and helium. Now, researchers at the Laboratoire d’Astrophysique de Marseille (CNRS/Aix-Marseille Université/Cnes)[1] have actually analyzed a brand-new possibility, particularly that the low density of mini-Neptunes might be discussed merely by the existence of a thick layer of water that experiences an extreme greenhouse result triggered by the irradiation from their host star.

These findings, just recently released in The Astrophysical Journal Letters, reveal that mini-Neptunes might be very-Earths with a rocky core surrounded by water in a supercritical state[2], recommending that these 2 kinds of exoplanet might form in the exact same method.

Another paper just recently released in Astronomy & Astrophysics, associating with France researchers generally from the CNRS and the University of Bordeaux[3], concentrated on the result of outstanding irradiation on the radius of Earth-sized worlds including water. Their work reveals that the size of the environments of such worlds increases significantly when based on a strong greenhouse result, in line with the research study on mini-Neptunes.

Future observations ought to make it possible to evaluate these unique hypotheses advanced by French researchers, who are making significant contributions to our understanding of exoplanets.


“Irradiated Ocean Planets Bridge 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, 15 June 2020, The Astrophysical Journal Letters.
DOI: 10.3847/2041-8213/ab9530

“Revised mass-radius relationships for water-rich rocky planets more irradiated than the runaway greenhouse limit” by Turbet, Martin; Bolmont Emeline; Ehrenreich, David; Gratier, Pierre; Leconte, Jérémy; Selsis, Franck; Hara, Nathan; Lovis, Christophe, 9 June 2020, Astronomy & Astrophysics.
DOI: 10.1051/0004-6361/201937151


  1. In cooperation with a scientist at the Laboratoire Atmosphères et Observations Spatiales (CNRS/UVSQ/Sorbonne Université)
  2. Supercritical water exists at really high pressures and temperature levels.
  3. The French researchers operate at the Laboratoire d’Astrophysique de Bordeaux (CNRS/Université de Bordeaux) and utilized a planetary environment design established at the Laboratoire de Météorologie Dynamique (CNRS/ENS Paris/Ecole Polytechnique– Institut Polytechnique de Paris/Sorbonne Université).

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