Wednesday, August 24, 2016

Proxima B: Life could possibly exist on this 'second Earth' is found orbiting "our" nearest Star in the Alpha Centauri system

An artist's impression of the newly discovered Proxima b planet which orbits our nearest star. 

Proxima Centauri is a red dwarf, a small low-mass star, about 4.25 light-years from the Sun in the constellation of Centaurus. Wikipedia Distance to Earth: 4.243 light years Radius: 100,900 km (0.145 R☉) Mass: 2.446 × 10^29 kg (0.123 M☉) Absolute magnitude: 15.49 Surface temperature: 3,042 K Luminosity: 0.0017 L☉

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 the Goldilocks Zone, where the temperature is mild enough for water to remain liquid.

See the video here.

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 discovery. Dr 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. Professor Stephen Hawking is currently devising a small spacecraft to travel to the Alpha Centauri star system in which Proxima Centauri resides in just 20 years.

It would use a 100-gigawatt beam of light to reach speeds of 100 million miles an hour. 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.

Proxima b orbits the red dwarf star Proxima Centauri which is 4.3 light years away from Earth CREDIT: ESO/M. KORNMESSER

“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. However its proximity its sun means it is blasted by powerful ultraviolet rays and X-rays so any life that evolved on its surface would have to have evolved to withstand the punishing radiation. Nevertheless, the prospect of finding life on Proxima b has excited scientists.

An infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System 

An infographic compares the orbit of the planet around Proxima Centauri (Proxima b) with the same region of the Solar System

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 the European Southern Observatory at La Silla in Chile's Atacama desert.

A view of the southern skies over the ESO 3.6-metre telescope at the La Silla Observatory in Chile with images of the stars Proxima Centauri (lower-right) and the double star Alpha Centauri AB (lower-left) from the NASA/ESA Hubble Space Telescope. CREDIT: Y. BELETSKY (LCO)/ESO/ESA/NASA/M. ZAMANI

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.

See this video here.

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. 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." The research was published in the journal Nature.