Earth-like planet with oceans is found just four light years away
A planet similar to Earth that may have deep oceans and even life has been discovered in another solar system just 4.27 light years away - close enough to be reached by future space missions.
The new world, bigger than Earth, orbits Proxima Centauri - our closest stellar neighbour.
It is now the primary target for Russian billionaire Yuri Milner's ambitious $100m plan to send a fleet of miniature interstellar probes fitted with cameras on a 20-year mission to search for alien life.
Breakthrough Starshot - which is backed by Professor Stephen Hawking - aims to accelerate the tiny one gram "nanocraft" to 20pc of the speed of light using "sails" pushed by a powerful laser.
The planet lies only 7.5 million kilometres from its parent star, 5pc of the distance between the Earth and the Sun, and takes just 11.2 days to complete one orbit.
But because Proxima Centauri is a dim red dwarf star radiating much less heat than the Sun, the planet occupies the "habitable zone" where temperatures are mild enough to permit liquid surface water.
Professor Richard Nelson, from Queen Mary University of London - a member of the international team that announced the discovery in the journal 'Nature' - said: "Finding a planet around the star which is the nearest to the Sun is a big event.
"Finding that the planet has certain characteristics that make it potentially Earth-like and habitable is even more exciting.
"My own view is that this planet probably has a significant amount of surface water. It's likely that it formed further out from the star before migrating in, and may have picked up a lot of icy material. I wouldn't be surprised if it had fairly deep global oceans."
One possible obstacle to life on Proxima b is that the planet would regularly be bathed in powerful ultraviolet radiation and X-rays from solar flares. But Prof Nelson does not think conditions on the planet's surface are too inhospitable for life.
Colleague Dr Guillem Anglada-Escude, also from Queen Mary University of London, who led the team of around 30 astronomers, said: "Succeeding in the search for the nearest terrestrial planet beyond the solar system has been an experience of a lifetime. We hope these findings inspire future generations to keep looking beyond the stars. The search for life on Proxima b comes next."