Kepler

By David S. Spiegel 

Sighting a deer outside of Fuld Hall; how long did Earth have to wait before life "walked into sight"?

Until a couple of decades ago, the only planets we knew existed were the nine in our Solar System. In the last twenty-five years, we’ve lost one of the local ones (Pluto, now classified as a “minor planet”) and gained about three thousand candidate planets around other stars, dubbed exoplanets. The new field of exoplanetary science is perhaps the fastest growing subfield of astrophysics, and will remain a core discipline for the forseeable future.

The fact that any biology beyond Earth seems likely to live on such a planet is among the many reasons why the study of exoplanets is so compelling. In short, planets are not merely astrophysical objects but also (at least some of them) potential abodes.

The highly successful Kepler mission involves a satellite with a sensitive telescope/camera that stares at a patch of sky in the direction of the constellation Cygnus. The goal of the mission is to find what fraction of Sun-like stars have Earth-sized planets with a similar Earth-Sun separation (about 150 million kilometers, or the distance light travels in eight minutes).