sentences:  Due to the proximity of Gliese 876 d to its host star (a red dwarf), it may have a surface temperature of 430–650 kelvins and be too hot to support liquid water.In April 2007, a team headed by Stéphane Udry based in Switzerland announced the discovery of two new super-Earths within the Gliese 581 planetary system, both on the edge of the habitable zone around the star where liquid water may be possible on the surface.With Gliese 581c having a mass of at least 5 Earth masses and a distance from Gliese 581 of 0.073 astronomical units (6.8 million mi, 11 million km), it is on the "warm" edge of the habitable zone around Gliese 581 with an estimated mean temperature (without taking into consideration effects from an atmosphere) of −3 degrees Celsius with an albedo comparable to Venus and 40 degrees Celsius with an albedo comparable to Earth.