Proxima b: Alien life could exist on 'second Earth' found orbiting our nearest star in Alpha Centauri system
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It is invisible to the naked eye from Earth and outshone by the bright glow of Alpha Centauri, but our closest star is holding an intriguing secret, scientists have discovered.
Proxima Centauri, which lies in our nearest star system, is orbited by a rocky planet that is so similar to Earth that it could harbour life.
The planet, dubbed ‘Proxima b’ is only four light years away, just next door in astronomical terms, and sits in a position known as theGoldilocks Zone, where the temperature is mild enough for water to remain liquid.
Hundreds of exoplanets have been discovered in recent years which could harbour life, but this is the closest to our solar system.
The planet is more than 25 trillion miles away, a distance that would take around 30,000 years to reach with current technology.
It is a great place to start looking for life outside the Solar System and it is a very exciting discoveryDr Mikko Tuomi, University of Hertfordshire
However, the planet is close enough to give scientists confidence that they can develop a space craft that would be able to reach it within the scale of a human life time and they 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.
Dr Mikko Tuomi, from the University of Hertfordshire, who was part of the discovery team, 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.
“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.
“It is a great place to start looking for life outside the Solar System and it is a very exciting discovery.”
Proxima b is only 4.4 million miles (7.5 million km) from its star, five 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 still occupies the habitable zone.
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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."
Proxima Centauri is part of a triple system of stars in the constellation of Centaurus. It is the faintest of the three, which also include a much brighter pair of stars known as Alpha Centauri A and B.
From Earth, the system appears as a single bright star - the third brightest visible in the night sky.
Astronomers made the discovery studying Proxima Centauri using a special instrument on the 3.6-metre telescope operated by theEuropean Southern Observatory at La Silla in Chile's Atacama desert.
The High Accuracy Radial Velocity Planet Searcher was able to measure the tiny "wobble" in the star's position caused by its interaction with the planet's gravity.
Shifts in the star's light spectrum showed that at times the star was approaching Earth at around human walking pace - about 3mph - and at other times receding at the same speed.
From this data the scientists were able to infer the presence of a planet around 1.3 times more massive than the Earth.
Because red dwarfs can mislead planet hunters by giving false signals linked to "star spots" - the equivalent of sun spots - the scientists had to be sure of their findings.
Initial hints of a planet were observed in March 2000 and it took another 16 years before sufficient evidence was available to justify announcing the discovery to the world.
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Co-author Dr John Barnes, from the Open University, said: "Once we had established that the wobble wasn't caused by star spots, we knew that that there must be a planet orbiting within a zone where water could exist, which is really exciting.
"If further research concludes that the conditions of its atmosphere are suitable to support life, this is arguably one of the most important scientific discoveries we will ever make."