In Search of Circumstellar Habitable Zones

Editor's Note: As a series at ENV, we are pleased to present "Exoplanets." Daniel Bakken is anengineer who teachesastronomy at the college level, and an entrepreneur in compound semiconductor crystal growth. In a series of articles he critically examines recent claims about exoplanets beyond our solar system, asking whether our own planet Earth is a rarity, or common, in the cosmos.

In the search for habitable planets, the circumstellar habitable zone is the spherical shell environment define...