Characterization of an aquatic world on an exoplanetary system

Artistic representation of an exoplanet orbiting a star. Credits: ESO/L. Calçada (modified)

A team of astronomers from 11 countries, led by researchers from Instituto de Astrofísica e Ciências do Espaço (IA), determined with precision the mass of two small exoplanets orbiting star HD 106315.

These two planets had already been detected by the transit method1 with satellite Kepler (NASA), which allowed the researchers to determine their diameters.

In combination with the now known mass, it was possible to determine the density of these planets. A more detailed study of the smallest planet among the two, using models of planetary interiors, indicated that up to 50% of the planet consisted of rocky material, and between 9 and 50% of water. Meaning, this is an aquatic world.

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  1. The Transit Method consists in the measurement of the decrease in the light of a star caused by the passing of an exoplanet in front of that star (like a micro-eclipse). Through a transit, one can only determine the radius of a planet. This method is complicated to use, as it requires that the planet(s) is/are exactly aligned with the observer’s view.