Model of a planet with a rocky core and a gaseous atmosphere. Image: UZH
Planet size puts limits on its chemical composition - space science news

A computational analysis has revealed that the chemical composition and structure of exoplanets has a so-called “threshold radius”, that sets limits as to what a planet can be made off. For instance, planets with a radius of 1.4 times that of the Earth can be earth-like, i.e. have a similar chemical composition than our planet. Planets with a radius above this will contain more silicates or other light materials, planets with a radius of more 1.6 times that of the Earth will have more hydrogen-helium gas and a rocky core. Big planets (with 2.6 times the radius of the Earth) cannot contain water, and the giant planets (with 4 or more times the radius of the Earth) would be very gaseous, much like Jupiter and Neptune in our solar system. Thus, this analysis provides an estimation of whether a planet is earth-like, is made of gas or rock, or is a water-world.

Read the full story: University of Zürich
Scientific publication: The Astrophysical Journal