What Kind of Stars Make Rocky Planets Like Earth?

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.

Their findings are published by The Astrophysical Journal.

“There has been much ongoing debate about the stellar conditions necessary for planet formation,” said lead author Simon Schuler of the University of Tampa. “Our results support the theory that the formation of small, rocky planets can occur around stars with diverse elemental compositions.”

“This means that small, rocky planets may be even more commonplace than we previously thought,” Teske added.

The planetary-formation from the gas-and-dust disk surrounding a new star as described above has also raised the question of whether the process itself depletes stars of the elements that are concentrated in the planets. If so, this could be used to improve our planet-searching abilities, as looking specifically for stars that show signs of this kind of chemical depletion could narrow the hunt. However, none of the seven stars the team studied displayed this suggested depletion signature.

“Finding small planets can be challenging, so it’s a little disappointing that we don’t have a clear pointer for finding their host stars,” Teske said. She works with Carnegie’s Paul Butler on one of the longest-running radial velocity planet searches, in which they are trying to find Earth-like planets. “However, at the same time our results are really exciting because they mean that small planets are very common and chemically diverse.”

Teske is presenting today at the Extreme Solar Systems III meeting, co-organized by the American Astronomical Society and Northwestern University’s Center for Interdisciplinary Exploration and Research in Astronomy (CIERA).