Rethinking where life could exist beyond Earth

Astronomers have long searched for life within a rather narrow ring around a star, the "habitable zone," where a planet should be neither too hot nor too cold for liquid water. A new study argues that this ring is too strict: on tidally locked worlds that keep one face in daylight and the other in permanent night, heat may still circulate enough for liquid water to persist on the dark side, even when the planet orbits closer to cool M- and K-dwarf stars than conservative climate models allow.