Where are the massive close-in extrasolar planets?

Kurzfassung

About 68 extrasolar planets around main sequence stars have been discovered. The minimum masses of these planets are ranging from fractions of a Jupiter mass to 15 Jupiter masses. The semi major axes of the planetary orbits range from 0.04 AU to 4 AU. Due to observational selection effects, only massive planets have been discovered at large semi major axes. However, there seems to be an observational lack of very massive planets (>1 Mj) for semi major axes less than 0.1 AU. The absence of massive planets at these distances is explained by tidal interactions between planets and their central star that lead to a rapid decay of the planet's orbit toward the Roche zone of the star within short time scales.