Free Astronomy Magazine January-February 2021

19 JANUARY-FEBRUARY 2021 ASTRO PUBLISHING our solar system, with its eight plan- ets, is an exception, and if this abun- dance may have played a role in the emergence of life on Earth. Back when the discoveries of new systems numbered only in the hundreds, it was observed that most exoplanets have orbits with an eccentricity value that is anything but negligible. In other words, their orbits are quite elongated, with many planets only passing through the habitable zone of their orbited star for a fraction of their year. Barring evolutionary paths that can accommodate extreme long freeze/short thaw cycles, this orbital elongation does not speak favorably for the habitability of those worlds. For as long as they have had orbital data to analyze from the first discov- ered exoplanets, astronomers have been trying to understand why plan- etary systems characterized by rela- tively eccentric orbits are so frequent and why those with orbits close to cir- cularity are instead so rare.