NASA

Although our catalog of exoplanets is expanding rapidly, researchers are still looking for one that can unequivocally play host to liquid water on its surface. Over the past several years, attention has focused on the collection of planets orbiting the red dwarf Gliese 581, which is only 20 light years from Earth. The star plays host to at least five planets, some of which have been put forth as candidates for habitability based on the presence of liquid water. A new climate model, however, has now shifted attention towards GJ581d, a super-Earth that was thought to be too cold to support liquid water.