Mini Neptunes, as their name suggests, would be miniature versions – about 2.4 times the Earth’s radius – of gas giants like Neptune. They are worlds devoid of a solid surface and made up mainly of hydrogen and helium, or so that’s what scientists believed.
That’s because a new study presented by researchers at the Laboratoire d’Astrophysique de Marseille, France, suggests that these little stars may also be rocky.
Among the characteristics that led scientists to classify Mini Neptunes as gaseous planets are the fact that they are less dense and have less mass than expected for a rocky world of the same dimensions. However, the surveys carried out by the Marseille researchers pointed out that the low density and mass can be easily explained.
According to the study, it may be that, instead of being gaseous, some Mini Neptunes are planets like Earth, only much larger, and harbor a thick layer of water. This means: a huge, highly pressurized and extremely heated ocean resulting from an intense greenhouse effect caused by the irradiation of its star.
In this sense, surveys on the impact of stellar radiation (that is, the amount of radiation per unit area) indicated that, on rocky planets with a radius similar to that of Earth and containing water, the size of the atmospheres increases greatly depending on the intensity of the effect greenhouse to which they are subjected.
Not that the gaseous Mini Neptunes do not exist, but what the research suggests is that there are also rocky Mini Neptunes, being possible that both are formed through the same process. This question of planetary formation is interesting, since astronomers believed that these 2 types of exoplanets belonged to completely different classes. So, if what was presented by the researchers in Marseille is confirmed, it may be that the Cosmos houses many worlds with great similarities between them.