Exoplanets

Until 1995, planets around other ordinary stars were no more than a conjecture. But in that year, two Swiss astronomers measured the slight wobble of the star 51 Pegasi, and opened up what is today one of the most energetic research disciplines in astrobiology: the hunt for, and quest to characterize, extrasolar planets (exoplanets). Given its interest in life beyond Earth, it’s hardly surprising that the SETI Institute is part of this effort. In the two decades since the discovery of the world around 51 Pegasi, thousands of exoplanets have been uncovered using the Kepler space telescope. Many Institute scientists are part of the Kepler research team, and others participate in the Kepler outreach program. While the first discovered exoplanets were bloated gas giants (Jupiter-size or larger), often orbiting very close to their home stars, the increasing sensitivity of exoplanet experiments has caused a shift in the type of planets being found. They are now predominately smaller worlds, comparable or somewhat larger than Earth. This augurs well for the existence of large numbers of habitable worlds in the cosmos, and tentative estimates suggest that as many as one-in-five or one-in-ten stars will harbor such bio-friendly planets. In addition to Kepler, SETI Institute researchers have been using the Gemini Planet Imager (GPI), a state-ofthe-art instrument in Chile that is able to directly photograph and characterize young Jupiter-size worlds around nearby stars. Some of the newly discovered exoplanets have become priority targets for the Institute’s SETI experiments. In addition, the fact that there are likely to be tens of billions of habitable worlds in our own galaxy serves as an encouraging impetus for such experiments.