Water World Found, It's a Mini-Neptune Made of Ice

Around a star very similar to the Sun, 564 light years away from the Solar System , there is a water world , a so-called ' water world ', that is, a planet composed largely of ice and perhaps also of a small percentage of liquid water: it is Kepler-10c, a mini-Neptune , on which light has finally been shed thanks to the most accurate estimate ever made of its mass and density , characteristics that until now have been the subject of very discordant and therefore very uncertain measurements. The result, which is being published in the journal Astronomy & Astrophysics and is now available on the arXiv platform , is due to the international study led by Italy with the National Institute of Astrophysics, in which the University of Padua, the University of Milan and the University of Turin also participated.

“ The existence of 'water worlds' has been predicted theoretically by models of planetary formation and migration, but we still don't have a certain confirmation,” says Aldo Bonomo of INAF in Turin, who led the researchers. “The proof of the existence of these planets should come from the study of their atmospheres with the James Webb space telescope (of NASA, the European and Canadian Space Agency) – adds Bonomo – because we expect them to have atmospheres particularly rich in water vapor ”.

The research, conducted using an instrument installed on the INAF's Galileo National Telescope, which scans the sky from the Canary Islands, has also confirmed the presence of another planet around the same star , previously hypothesized but never directly observed. Its existence was revealed by a small anomaly that it induces in the orbit of Kepler-10c: it is in exactly the same way that Neptune was discovered in 1846, based on the anomalies it causes in the orbit of Uranus. Thanks to the exceptional quality of the measurements carried out by the TNG, it was possible to calculate the orbital period of the 'ghost' planet , which is 151 days , while that of Kepler-10c is 45 days .