“Circle of Life”

If there’s life elsewhere in the galaxy, or elsewhere in the universe, a recent study by Mary Anne Limbach and Edwin L. Turner of Princeton University suggests that it will occur in solar systems with a relatively high number of planets following roughly circular orbits.

The necessity of circular or nearly-circular orbits is fairly obvious:  If a planet periodically came too close to its sun and then veered away too far into space, its temperatures would vary to such extremes that life would be almost impossible.

Perhaps the more surprising aspect of the study, which was originally published in the Proceedings of the National Academy of Sciences but is summarized in a brief article in the March 2015 issue of Scientific American entitled “Circle of Life,” is that solar systems with higher numbers of planets tend to have more regular (i.e., more nearly circular) orbits.