The extreme gravity would make walking impossible, and the sunlight is so fierce that developing cancer would be inevitable. Yet planet K2-18b, which lies 110 light years away in the constellation Leo, is the first world ever discovered which could realistically support alien life.

In a groundbreaking breakthrough, scientists at University College London (UCL) have found that the rocky planet contains liquid water and has an atmosphere, raising the first real hope of finding living extra-terrestrial organisms somewhere other than Earth.

Water was detected by measuring light waves filtering through hydrogen molecules in the planet’s atmosphere, in archived data captured by the Nasa’s Hubble Space Telescope in 2016 and 2017.

Although Hubble did not carry any instruments capable of spotting signs of life - such as methane - new telescopes will soon be launched which can hunt for biosignatures, and may finally answer the question of whether we are alone in the universe.

Dr Angelos Tsiaras, of UCL’s Centre for Space Exochemistry Data, said: “Finding water in a potentially habitable world other than Earth is incredibly exciting.

“This is the only planet we know outside of Solar System that has the correct temperature for liquid water, making it the best candidate for habitability that we know right now.