The high density of the recently discovered close-in extrasolar planet HD149026b suggests the presence of a huge core in the planet, which challenges planet formation theory. We first derive constraints on the amount of heavy elements and hydrogen/helium present in the planet: We find that preferred values of the core mass are between 50 and 80M ⊕ , although a minimum value of the core mass is ...

Giant planets orbiting stars other than the Sun are clearly detectable through precise radial-velocity measurements of the orbital reflex motion of the parent star. In the four years since the discovery 1 of the companion to the star 51 Peg, similar low-amplitude " Doppler star wobbles " have revealed the presence of some 20 planets orbiting nearby solar-type stars. Several of these newly-disco...