The planet — host star metallicity connection has been one of the most secure and enduring results from the radial velocity planet surveys. In 1997, soon after the detection of the first planets, Guillermo Gonalez pointed out that the host stars were significantly enriched in elements heavier than hydrogen and helium, and suggested that a planet-metallicity connection exists.
Over the years, the correlations have been refined by many different workers, and a clear set of facts has emerged:
(1) Giant planet hosts, all the way from low-mass red dwarf stars through stars that are somewhat hotter and more massive than the Sun, tend to be metal rich.
(2) The occurrence rate for giant planets increases with stellar mass.
(3) Among stars with mass similar to the Sun, there’s no evidence that the presence of sub-Neptune/super-Earth is correlated with host star metallicity.
Taken together, these facts provide basic support for the core-accretion mechanism of giant planet formation. A planet like Jupiter forms by first assembling a core of icy/rocky/metallic material. When the core mass grows to of order 10-20 Earth masses, the core gains the ability to very rapidly accrete hydrogen and helium, and increases its mass by a significant, ...