Astronomers have just announced (New York Times article) the discovery of a fourth planet orbiting the nearby star Gliese 581. This planet is also the most earth-like, in terms of mass, of the more than 300 extrasolar planets yet discovered.

This newly discovered planet is much too close to its parent star to be conducive to life. However, the outermost planet in the Gliese 581 system is just outside (or possibly just within) the boundary of the habitable zone, which is defined as the region around a star where liquid water might exist on the surface.

The recently developed Stellar Habitability Zone simulator can be used to model this system as well as several others. This simulator is part of an extrasolar biology NAAP module currently under development.