A “super-Earth” 1,400 light years away has emerged as the exoplanet most likely of any known to support alien life.
Kepler 452b, discovered in 2015, lies in the middle of a newly identified “abiogenesis zone” where the right conditions exist for life to be spawned by starlight and chemistry.
The planet, which has a radius 1.5 times that of Earth, also orbits inside the “habitable” or “Goldilocks” zone with temperatures not too hot and not too cold to permit liquid surface water.
Almost 4,000 planets have now been discovered orbiting stars other than the sun. Of these, only about 50 are known to occupy their star’s habitable zone.
However, just one – Kepler 452b – also falls inside the abiogenesis zone.
A planet in the abiogenesis zone is bathed in the right level and type of ultraviolet radiation from its star to kick-start chemical reactions thought to have given birth to life on Earth.
Scientists at Cambridge University coined the term after conducting a series of laboratory experiments mimicking the creation of life’s building blocks.
A leading theory for the way life began on Earth is that it emerged from chemical reactions involving hydrogen cyanide and hydrogen sulphite, powered by sunlight.
Duplicating earlier work conducted in 2015, the Cambridge researchers created the precursors of lipids, amino acids and nucleotides – all essential components of living cells.
They then went a step further by comparing the UV light used in the laboratory to that generated by different stars.
Generally the most sun-like stars were found to emit the right sort of light to trigger the formation of life’s building blocks on planets.
Kepler 452, in the constellation of Cygnus, is about 20% brighter than the sun and some two billion years older.
The planet 452b has been called “Earth’s cousin”. Computer simulations suggest it has a thick atmosphere, liquid surface water, and active volcanoes.
Lead scientist Dr Paul Rimmer, from Cambridge University’s Cavendish Laboratory, said: “This work allows us to narrow down the best places to search for life.
“It brings us just a little bit closer to addressing the question of whether we are alone in the universe.”
Most known habitable zone planets orbit close to cool red dwarf stars. Occasional violent flares from the stars could provide the radiation needed to spark the birth of life, but may also destroy genetic material, said the scientists.
The new research is published in the journal Science Advances.
According to recent estimates, there could be as many as 700 million trillion Earth-like planets in the observable universe.
Dr Rimmer said: “I’m not sure how contingent life is, but given that we only have one example so far, it makes sense to look for places that are most like us.
“There’s an important distinction between what is necessary and what is sufficient. The building blocks are necessary, but they may not be sufficient: it’s possible you could mix them for billions of years and nothing happens. But you want to at least look at the places where the necessary things exist.”
Next generation space telescopes such as Nasa’s Tess and James Webb telescopes may identify many more planets lying within abiogenesis zones, said the scientists.