It is now well established that planets form within a few million years from the dusty, circumstellar disk of young stars. It is thus expected that the properties of the planets must be closely related to the structure, lifetime, mass, and chemical composition of the disk, but how they relate to each other is not known. Finding such correlations would give us key information on how planets form. In order to find out how the properties of the planets relate to the properties of the disk, we have to take a statistical approach.
Theoretical studies have shown that more massive stars should also have more massive planets, because they had more massive disks (Kennedy & Kenyon 2008). This prediction is in fact confirmed observationally; intermediate-mass stars (1.3–2.1M⊙) have twice as many massive planets as Solar-like stars, and they can also have planets that are much more massive thanSun-like stars (Johnson et al. 2010a, 2010b; Vigan et al. 2012).
PLATO is the first mission to allow the study of how the planet population changes with the mass of the host star over a wide range of masses, for a large number of targets. Since we now know, thanks to Spitzer and Herschel observations, how the average properties of disk change with the mass of the host star, we will for the first time be able to statistically relate properties of the disks with the properties of the planets. A key question to be addressed is: how do the properties of planets change with the mass of the host stars?