Planets pack tightly in the Milky Way
Planetary systems in our galaxy are packed to the brim, according to a new study — throw in another orb and all hell will break loose. The study, posted February 28 at arXiv.org, argues that planets around other stars share an evolutionary history similar to that of the solar system’s eight planets.
“This study supports results that have been building for a long time,” says Jack Lissauer, a space scientist at NASA Ames Research Center in Moffett Field, Calif., who was not involved in the study. In 2011, he discovered Kepler-11, a star with planets so tightly packed around it that five of them have smaller orbits than Mercury’s.
About 25 years ago, astrophysicists examining the solar system’s planets realized that their orbits teeter on the edge of instability. Add another world, and the eight planets would start pulling each other into new, unstable