The Evolution of an Earth-Like World
Lying 22.1 light years from Earth is Gliese 667. Unlike Gliese 581, the Gliese 667 system is a far more interesting construct. For one thing there are three stars, not one. Two of these stars, 667A and 667B, are low mass, K-class orange dwarfs (Chap. 3) orbiting their common center of gravity. The orbit of both K-stars is very eccentric, with their separation varying from 5 to 20 A.U. – roughly the Sun-Jupiter distance at the closest approach, to the Sun-Uranus distance when furthest apart. The stars weigh in at 0.73 and 0.69 solar masses, or roughly three quarters that of our Sun. In terms of size each star more fully approaches that of the Sun rather than Jupiter (Table 10.1).