New evidence indicates that rocky, Earth-like planets can form around a diverse range of stars, suggesting that the universe holds many more of the planets than previously thought. The finding could have important consequences for the hunt for extraterrestrial life.
"Potentially habitable planets can form around virtually any kind of star"
Using data from Nasa’s Kepler spacecraft, researchers around the US and Europe surveyed upward of 150 stars known to have planets, correlating the metallicities of the stars with their planets’ sizes. In astronomer speak, "metals" are elements other than hydrogen or helium — for example, silicon and oxygen, key components of rocks. Metals take time for stars to cook up, so if rocky planets are only found around highly metallic stars, life would have to be a relatively recent development. According to David Latham, a lead researcher on the project, "giant planets prefer metal-rich stars. Little ones don’t," suggesting that "terrestrial worlds could form at almost any time in our galaxy’s history." The results of the study have been published in the journal Nature.
In order to find out what the study means for the possibility of life outside our solar system, io9 spoke with Seth Shostak, Senior Astronomer at the SETI Institute. "The message we’ve been getting from the planet hunting community is loud and clear, and that message is that all stars have planets," said Shostak. Since life is potentially everywhere, he would like to focus more of the institute’s attention on the dense center of our galaxy. "Now that we know that potentially habitable planets can form around virtually any kind of star, it’s important to focus our attention on star-rich areas"