The laws of physics potentially allow one binary star system to contain a surprisingly large number of Earth-like planets, assuming there is enough matter.
Why settle for one habitable planet, when you can have 60? An astrophysicist has designed the ultimate star system by cramming in as many Earth-like worlds as possible without breaking the laws of physics. Such a monster cosmic neighbourhood is unlikely to exist in reality, but it could inspire future exoplanet studies. Sean Raymond of Bordeaux Observatory in France started his game of fantasy star system with a couple of ground rules. First, the arrangement of planets must be scientifically plausible. Second, they must be gravitationally stable over billions of years: there is no point in putting planets into orbit only to watch them spiral into the sun.
"The arguments were based on the recent scientific literature as well as some simple calculations I did," says Raymond. In some cases it was impossible to choose between two scenarios because of a lack of data, so he just picked the one he liked best.
Gas giants such as Jupiter are not habitable to life as we know it, but they can be orbited by Earth-like moons. In our solar system, Europa and Enceladus, which orbit Jupiter and Saturn, respectively, are prime candidates for extraterrestrial life. Raymond calculates that a red dwarf could hold four Jupiter-like planets, each with five Earth-like moons. What's more, the Trojan trick can allow another two Earth-like planets on either side of the orbiting Jupiters, upping the total number of habitable worlds around the red dwarf to 36.
Finally, Raymond turned his star system into a binary one, with two red dwarfs separated by roughly the distance from our sun to the edge of the solar system. Theory allows one star to carry the Earth-only configuration, and the other to carry the Earth-plus-Jupiters configuration. This creates the ultimate star system, with 60 habitable planets to choose from.