We review the interior structure and evolution of Jupiter, Saturn, Uranus and Neptune, and extrasolar giant planets with particular emphasis on constraining their global composition.

We report the first unambiguous detection of X-ray emission originating from Saturn with a Chandra observation, duration 65.5 ksec with ACIS-S3. Beyond the pure detection we analyze the spatial distribution of X-rays on the planetary surface, the light curve, and some spectral properties. The detection is based on 162 cts extracted from the ACIS-S3 chip within the optical disk of Saturn. We fou...

The planets of the outer Solar System are Jupiter, Saturn, Uranus and Neptune. The former two are the giant planets, the latter two are also known as sub-giants. The planets are significantly more massive (compare Table 1 of Section 4.2.2.2) than the terrestrial planets and have considerably larger radii. Their mean densities are much smaller, between roughly 690 kg/m (Saturn) and 1640 kg/m (Ne...