Host Star Metalicity has NOTHING to do With Whether or not Rocky Planets Form

As astronomers continue to find more and more planets around stars beyond our own Sun, they are trying to discover patterns and features that indicate what types of planets are likely to form around different kinds of stars. This will hopefully inform and make more efficient the ongoing planet hunting process, and also help us better understand our own Solar System's formation.

When a star is young, it is surrounded by a rotating disk of gas and dust, from which its planets form. As such, it's expected that chemical composition of the star should in some way affect the compositions of the planets orbiting it. Indeed, previous research has demonstrated that gas giant planets preferentially form around iron-rich stars. But more recent results have started to suggest that smaller planets do not require such high iron content in their stars to form.

New work from a team including Carnegie's Johanna Teske extended this idea by measuring a large suite of elements besides iron. They found that stars with Earth-sized rocky planets are overall chemically similar to those with Neptune-sized planets, and to stars with no planets, but not to stars with gas giant planets

The team examined the abundance of 19 different elements found in seven stars that are orbited by at least one Earth-like rocky planet, all discovered by NASA's Kepler mission. Their work shows that small rocky planets like Earth do not preferentially form around stars rich in metallic elements such as iron and silicon. The result is surprising because iron and silicon are among the most abundant elements in rocky planets.

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