Colloquium: Stars, planets, and metals

The discovery in 1995 of the first planet orbiting another Sun-like star stimulated renewed interest in planet formation and evolution processes. A number of trends among the properties of the planets have become evident in the years since. An interesting pattern began to emerge in 1997—stars hosting planets tend to be more metal rich (i.e., have more abundant elements with Z>2) than the average nearby star. Other, more subtle, trends are beginning to appear as the sample size continues to grow; for example, the masses of stars hosting planets are found to correlate with their metallicities. The author reviews the state of our knowledge concerning the observed trends, their possible causes, and their possible implications for astrophysics and astrobiology.