A Comprehensive Comparison of the Sun to Other Stars: Searching for Self-Selection Effects

Abstract

If the origin of life and the evolution of observers on a planet is favored by atypical properties of a planet's host star, we would expect our Sun to be atypical with respect to such properties. The Sun has been described by previous studies as both typical and atypical. In an effort to reduce this ambiguity and quantify how typical the Sun is, we identify 11 maximally independent properties that have plausible correlations with habitability and that have been observed by, or can be derived from, sufficiently large, currently available, and representative stellar surveys. By comparing solar values for the 11 properties to the resultant stellar distributions, we make the most comprehensive comparison of the Sun to other stars. The two most atypical properties of the Sun are its mass and orbit. The Sun is more massive than 95% ± 2% of nearby stars, and its orbit around the Galaxy is less eccentric than 93% ± 1% of FGK stars within 40 pc. Despite these apparently atypical properties, a χ2 analysis of the Sun's values for 11 properties, taken together, yields a solar χ⊙2 = 8.39 ± 0.96. If a star is chosen at random, the probability that it will have a lower value (i.e., be more typical) than the Sun, with respect to the 11 properties analyzed here, is only 29% ± 11%. These values quantify, and are consistent with, the idea that the Sun is a typical star. If we have sampled all reasonable properties associated with habitability, our result suggests that there are no special requirements for a star to host a planet with life.