A planet similar to Earth that may have deep oceans and harbour life has been discovered in another solar system just 4.27 light years away - close enough to be reached by future space missions.

Astronomers from the University of Hertfordshire have played a key role in the discovery of Proxima b, which has been found in the Habitable Zone around Proxima Centauri, the closest star to our Sun.

Proxima Centauri itself is part of a triple system of stars in the neighbouring Solar System of Alpha Centauri, some 4.2 light years away from Earth (approximately 25.2 trillion miles) and also the target of humankind’s first attempt to travel to another star system, the StarShot project.

Dr Mikko Tuomi, from the centre for astrophysical research at the University of Hertfordshire, said: "According to the findings 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."

The discovery, published in the journal Nature, was made as part of a collaborative project with the European Southern Observatory (ESO) and other academic institutions.

Scientists have calculated that Proxima b is about 1.3 times more massive than the Earth and probably rocky.

It lies only 7.5 million kilometres from its parent 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, the planet occupies the "habitable zone" where temperatures are mild enough to permit liquid surface water.

The announcement of the new found planet has been a long time in the making.

Professor Hugh Jones from the University of Hertfordshire explained: "Initial observations of the planet were made more than 15 years ago in March 2000. We first submitted a scientific paper presenting the planet’s existence back in February 2013.

"My colleague Dr Mikko Tuomi had discovered the planet's fingerprints in archived data taken before 2009, but we didn’t have enough evidence to conclusively support such a major discovery.

"Dr Guillem Anglada-Escude then joined the University of Hertfordshire team and coordinated major observing campaigns.

"These gave us enough observations to unequivocally confirm the planetary signal with several independent datasets."

A crucial aspect was to be sure the signal was due to a planet. This was established by Dr John Barnes, also formerly a researcher at the University of Hertfordshire now based at the Open University and Dr James Jenkins, a former University of Hertfordshire PhD student, now at the University of Chile.

The final campaign involved the University of Hertfordshire working as part of the ESO project called The Pale Red Dot, a coordinated international effort involving more than 30 scientists from eight different countries across three continents.

As a result, the University of Hertfordshire’s Bayfordbury Observatory now has a major monitoring programme aimed at other nearby stars like Proxima.

Speaking on the possibility of life being found on the planet, Dr Tuomi, said: "If Proxima b has an atmosphere and if there is water there, and these are big ‘ifs’, it is intriguing to think that the simple ingredients - water, carbon dioxide, and rock - that are needed for the formation of biochemical cycles that we call life, could all be present and interacting on the planet’s surface.

"We need to study this system a lot more over the coming decades in order to be able to start answering such questions. However, it is a great place to start looking for life outside the Solar System and it is a very exciting discovery."