Astronomers of the Flataron Institute in the United States revealed why there is a mysterious gap between the supermenities and mini-neptum, which is characterized by the almost complete absence of planets having a size of 1.5-2 radius of the Earth. Scientists submitted their findings in the article published in The Astronomical Journal.
Researchers analyzed the data collected by the KEPLER cosmic telescope using the transit method, when the desired exoplanet overshadows the light of the parent star. This approach allows you to estimate the size of the planet. It turned out that, if you divide the planets for young and old (older than two billion years), then rarely encountered radii were, on average, less for a young population exoplanet. With the age of the planet, this indicator shifts from 1.6 radius to 1.8 earth radius.
This is explained by the fact that over time mini-neptune lose the gas shell, and their size decreases. It remains only a solid rocky core, which is considered superer. The gap in radius decreases, since later larger mini neptunes also turn into the supest, decreasing to ten times. The loss of the atmosphere occurs both due to the intensive radiation of the parent stars and due to the residual heat of the planet, which has preserved after its formation.