The Failure of Early Optimism

When the first edition of this book was written there were only two plausible candidate systems that might host planets in their stars’ habitable zone, Gliese 581 and Gliese 667C. Both systems hosted a number of super-terrans, whose numbers varied often by the month as radial velocity data was interpreted, reinterpreted, discarded, recovered—only for vexing to continue. Obviously, like many of the authors of the papers upon which the book was centered, hyperbole tended to replace considered thought as the possibility of fame and further grants beckoned. The Gliese 581 system was a source of particular ire as rival groups made claims for the existence of planet 581g, which was at the time the best candidate for an Earth-like world—albeit a tidally locked one. This chapter rounds up some of the acrimony and resolution that surrounded the dissection of these star systems and discusses, in the light of the earlier chapters, just how habitable these worlds really were.