Another interpretation that is possible from these data rests on the fact that systems of high metallicity preferentially form more massive planets, which are thus easier to detect with current methods. Finally, we should note that the Solar System is actually located in the metallicity zone where the probability of finding planets is low ...

Another theory proposed to explain the excess metallicity is the presence of planets that have been engulfed and increased the metallic concentration of the star. Even if the hypothesis of the primordial composition of the protoplanetary disk is generally preferred, the hypothesis of planets being engulfed is not completely eliminated, and has been reconsidered using recent models of the convective layers in stars.

3.7 Mass/Diameter Ratio

Some objects (a good dozen) have been observed by two different methods: the radial-velocity method, which gives the mass of the object; and the transit method, which gives the diameter7. This enables us to obtain information about the average density of the planet. In certain cases, the transit has been observed by space telescopes (HST, Fuse, Spitzer, etc.), allowing accurate and chromatic measurements of the planet's diameter, leading to information about its atmospheric structure and composition (as described in the next paragraph). Figure 3.9 shows the relationship between the masses of planets observed in transit and their radii. Theoretical studies

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