Sigma Xi Publications



American Scientist

Are There Other Earths: Recent astronomical discoveries show our planet is far from average

The past decade has seen an explosion of discoveries of planets outside of our Solar System, dubbed extrasolar planets, or simply exoplanets. Many of the first exoplanets identified were large, about the size of Jupiter, and orbiting close to their parent stars. But such planets are not likely to harbor liquid water nor, therefore, life. More advanced techniques have allowed astrophysicists to locate exoplanets such as the one illustrated here, Kepler-138b, which was the first exoplanet discovered that has a mass and size smaller than Earth (planets are not shown at scale to star). Planets in what’s called the habitable zone around their stars could have liquid water on their surfaces. But as Howard A. Smith argues in “Questioning Copernican Mediocrity” (pages 232–239), a significant number of additional factors are needed to determine whether intelligent life might exist elsewhere in the universe. (Image courtesy of SETI Institute/Danielle Futselaar and NASA.)

July-August 2017

Sigma Xi Publications