A new study in Astrophysical Journal Letters suggests the atmosphere of planet Gliese 581d, which orbits a red dwarf star 20 light years away, could keep the planet warm enough for water, the BBC reports. The planet is at the outer edge of the “Goldilocks zone,” where liquid water could be sustained, and was discovered in 2007. That planet and another one in its solar system, Gliese 581g, have both been considered potentially habitable, although the existence of Gliese 581g has since been called into question. Planet 581d has a mass about six times that of Earth, and is about twice its size. It was originally thought to be too cold for liquid water, but French researchers ran computer simulations of its atmosphere—which they believe has a high concentration of carbon dioxide—and they believe it could host oceans of liquid water, clouds and rainfall.