This file compliments the Gliese 581 system with two more planets, Gliese 581 f and Gliese 581 g.
Gliese 581 g has attracted attention because it is near the middle of the habitable zone of its parent star. That means it could sustain liquid water on its surface and could potentially host life similar to that on Earth. Gliese 581 g is considered a super-Earth and is the planet closest in size to Earth known in a habitable zone.
However, the orbit and the other elements are not based on research. It's just my own interpretation.
1. Add Gliese 581.sc into your /catalogs/planets folder.
2. Open /config/universe.cfg and go to the PlanetsCatalogs section, add "catalogs/planets/Gliese 581.sc".