Up to 74% of planets in the ‘habitable zone’ may not be good for life

Many planets that have the right temperatures for liquid water on their surfaces used to be too hot or too cold, which may affect their ability to host life now

By Leah Crane

A large proportion of planets in the so-called habitable zone – the area in orbit around a star where conditions are right for liquid water on a world’s surface, and thus potentially for life – weren’t always there. That might mean that we are vastly overestimating the number of worlds that could host life.

While researchers often think of the habitable zone of any given star as being relatively static, it actually changes as the star evolves and its brightness and temperature …