A rocky planet that may harbour life has been discovered in another solar system just four light years from Earth – close enough to be reached by future space missions.
The new world, slightly more massive than Earth, orbits Proxima Centauri, our closest stellar neighbour.
In terms of astronomical distance, the planet – Proxima b – is right next door. Whether or not anything lives there remains open to speculation, but scientists believe that theoretically it could be habitable.
While four light years is a long way – more than 25 trillion miles –the planet is near enough to be reached by space craft within the scale of human life times.
Experts believe robotic probes could be sent to Proxima b in years to come. Much further in the future, the planet may even be colonised by space travellers from Earth, assuming conditions on the surface are survivable.
One possible obstacle to life evolving on the planet is the way it hugs its parent star.
Proxima b is only 7.5 million kilometres from the star, 5 per cent 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, it still occupies the “habitable zone” where temperatures are mild enough to permit liquid surface water.
On the other hand, the planet is blasted by powerful ultraviolet rays and X-rays from the star. Any life that evolved on its surface would have to be hardened against the radiation.
Nevertheless, the prospect of finding life on Proxima b has excited scientists.
Dr Guillem Anglada-Escude, from Queen Mary University of London, who led an international team of about 30 astronomers, said: “Succeeding in the search for the nearest terrestrial planet beyond the solar system has been an experience of a lifetime, and has drawn on the dedication and passion of a number of international researchers.
“We hope these findings inspire future generations to keep looking beyond the stars. The search for life on Proxima b comes next.”
Colleague Dr Mikko Tuomi, from the University of Hertfordshire, said: “The planet has a rocky surface and is only a fraction more massive than the Earth. It is the closest possible exoplanet to us and may be the closest to support life outside the solar system.”
Astronomers made the find, reported in the journal Nature, after studying Proxima Centauri using a 3.6-metre telescope in Chile’s Atacama desert.