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Planet discovered that could contain alien life

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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 known as 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 – future generations of super-fast space craft could conceivably travel to the planet within the scale of human life times.

Proxima Centauri planet.
Researchers believe Proxima b could hold signs of life (M Kornmess/ESO)

Experts have not ruled out the possibility of robotic probes being sent to Proxima b. 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 and flourishing on the planet is the way it hugs its parent star. Proxima b is only 7.5 million kilometres from the star, 5% 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 Mikko Tuomi, from the University of Hertfordshire, who was part of a team of about 30 astronomers involved in the research, 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.”

Proxima Centauri taken by Hubble Telescope.
Proxima Centauri taken by Hubble Telescope (Nasa)

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, reported in the journal Nature, after studying Proxima Centauri using a special instrument on the 3.6-metre telescope operated by the European Southern Observatory (ESO) at La Silla in Chile’s Atacama desert.

The High Accuracy Radial Velocity Planet Searcher (HARPS) was able to measure the tiny “wobble” in the star’s position caused by its interaction with the planet’s gravity.

Proxima Centauri planet.
Scientists believe the planet has a rocky surface and is only a fraction more massive than the Earth (M Kornmess/ESO)

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 orbiting at a distance of 7.5 million kilometres.

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 15 years before sufficient evidence was available to justify announcing the discovery to the world.




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