For over fifty years, astronomers have scoured the Milky Way Galaxy in search of a star that qualifies as the Sun’s twin. Given the Milky Way’s life-friendly features and two hundred billion stars, the astronomical community expected to find many exact analogs. However, by October 2007, in spite of diligent searches spanning several decades, astronomers had found only two possibilities: 18 Scorpii and HD 98618.3 Table 8.1 lists their observed properties:
