Planetary radii

Transiting planets offer the possibility to study the radii of extrasolar planets. The number of transiting planets is still too small to draw very significant statistical

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Fig. 1.5. The RV curve of u Andromedae, after removing the motion caused by the shortest-period planet. Note the non-periodic nature of the motion, which is the sum of the motions caused by the two outer planets. From Butler et al. (1999).

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Fig. 1.5. The RV curve of u Andromedae, after removing the motion caused by the shortest-period planet. Note the non-periodic nature of the motion, which is the sum of the motions caused by the two outer planets. From Butler et al. (1999).

Fig. 1.6. Mass-radius relation for known transiting planets. The triangles represent Jupiter and Saturn. The dashed lines are constant density lines, for densities of 0.4, 0.7, and 1.3 gcm-3. The dotted line represent levels of photometric precision required for detecting planets orbiting Sun-like stars.

Fig. 1.6. Mass-radius relation for known transiting planets. The triangles represent Jupiter and Saturn. The dashed lines are constant density lines, for densities of 0.4, 0.7, and 1.3 gcm-3. The dotted line represent levels of photometric precision required for detecting planets orbiting Sun-like stars.

conclusions, but it is worthwhile to examine the data. Figure 1.6 shows the massradius diagram of the ten transiting planets, together with Jupiter and Saturn for comparison, and representative isodensity lines. Early attempts to compare such diagrams with theoretical predictions seem promising (e.g., Guillot (2005), Laughlin et al. (2005)). It seems that most hot Jupiters have sizes close to that of Jupiter itself, and therefore their structure is not significantly perturbed by their proximity to the star.

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