MPS Seminar: Where are all the water worlds - Exoplanet system detection & characterization with Gaia (Simon Albrecht)

A recent high-profile study suggested the existence of a distinct population of water worlds—planets with significant water content. In the first part of this talk, I revisit this claim using an updated and expanded sample along with alternative statistical tools, showing that the data support only two populations: rocky super-Earths and gas dwarfs, with no compelling evidence for a third, water-rich group.

The second part of the talk focuses on how current and upcoming data from Gaia are enabling entirely new types of investigations. I will begin by discussing the detection and confirmation of substellar companions using Gaia Data Release 3 (DR3) in combination with radial velocity (RV) data. I will then present results from our ongoing RV follow-up campaigns in both the Northern and Southern hemispheres, including recent planet confirmations and the identification of false positives. Next, I will highlight findings based on Gaia’s <vbroad> parameter, revealing a strong correlation between orbital eccentricity and spin–orbit misalignment in binary stars. With Gaia DR4, this technique will become applicable to exoplanet systems as well. I will conclude with an outlook on what we can expect, using DR4 epoch astrometry, for mutual orbital inclination measurements — an important step forward in constraining planetary architectures and formation histories