A new planet which could contain life has been discovered close enough to Earth to be reached by future space missions.
The new world, which is slightly larger than our planet, is just four light years away in another solar system.
Named Proxima b by astronomers, the rocky planet orbits our closest stellar neighbour, Proxima Centauri.
While in terms of astronomical distances Proxima b is right next door, four light years is 25 trillion miles, but astronomers believe that future generations of super-fast space craft could conceivably travel to the planet within the scale of human lifetimes.
Theoretically Proxima b could be habitable as although it is 4.7 million miles from Proxima Centauri - five per cent of the distance between the Earth and the Sun - the star is a dim red dwarf star which radiates much less heat than the sun, meaning that temperatures are mild enough to allow liquid surface water.
However, the planet is also blasted by powerful ultraviolet rays and X-rays from the star, meaning that any life which evolved on the planet would have to be hardened to radiation.
Astronomers have not ruled out the possibility of robotic probes being sent to the planet, and in the future it could even be colonised by space travelers from Earth, assuming conditions on the surface are survivable.
Initial hints of a planet were observed in March 2000, but it took astronomers 15 years before enough evidence was available to justify announcing the discovery to the world.