cylonlover writes with news of an update to the model used for calculating the habitable zone around stars shifting things out a bit. From the article: "Researchers at Penn state have developed a new method for calculating the habitable zone (original paper, PDF) around stars. The computer model based on new greenhouse gas databases provides a tool to better estimate which extrasolar planets with sufficient atmospheric pressure might be able to maintain liquid water on their surface. The new model indicates that some of the nearly 300 possible Earth-like planets previously identified might be too close to their stars to to be habitable. It also places the Solar System's habitable zone between 0.99 AU (92 million mi, 148 million km) and 1.70 AU (158 million mi, 254 million km) from the Sun. Since the Earth orbits the Sun at an average distance of one AU, this puts us at the very edge of the habitable zone."