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New Earth-like planet found orbiting nearest star

25 August 2016

Scientists now have clear evidence of an ‘Earth-like’ planet, with the potential to support surface water and life, orbiting the closest star to our Solar System.

Artist's impression of the planet orbiting Proxima Centauri (Credit: European Southern Observatory (ESO))

‘Proxima b’ is a rocky planet that is more massive than Earth and revolves around its parent star every eleven days. Its condition, and its positioning in the habitable zone around Proxima Centrauri, which is the star closest to our Sun, means that liquid water and life could exist on its surface.

The results from an international team led by UK astronomers funded by STFC and who were using European Southern Observatory facilities as well as other telescopes are published in the journal Nature.

Proxima b which is 4.2 light years away (about 25.2 trillion miles) has excited scientists because it may also be the closest possible home for life outside of our Solar System.

Lead author and coordinator of the project, Dr Guillem Anglada-Escudé from Queen Mary University of London’s School of Physics and Astronomy, 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."

Professor Hugh Jones from the University of Hertfordshire says the announcement of the new found planet has been a long time in the making, “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. Guillem Anglada-Escudé then joined the University of Hertfordshire team and co-ordinated major observing campaigns. These gave us enough observations to unequivocally confirm the planetary signal with several independent datasets”.

Three UK universities, also including the Open University, were involved in the work, which included funding from the Science and Technology Facilities Council. STFC also manages the UK subscription to ESO.

Science Minster Jo Johnson said "the discovery of Proxima b adds to what has already been a momentous year for UK space research. It is yet another prime example of the pioneering and collaborative work of the scientists and researchers across the UK, and government’s commitment to increase our science budget will help support them to make even more exciting discoveries.”

Business and Energy Secretary Greg Clark said “following the record-breaking experiments conducted by Tim Peake on board the International Space Station, the discovery of Proxima b is another significant step forward for our understanding and knowledge of space. And this latest development is testament to the hard work and scientific endeavour of UK institutions who are leading the charge and making discoveries that could change lives and inspire millions around the world.”

During the first half of 2016, Proxima Centauri was regularly studied with the HARPS spectrograph at ESO’s La Silla observatory in Chile, and simultaneously monitored by other telescopes around the world.

Planet-hunters use the Doppler Effect, the shift in the star’s light spectrum depending on its velocity, to investigate the properties of exoplanets, such as their masses and periods of orbit.

The results indicate that at times Proxima Centauri is approaching Earth at around normal human walking pace (about 3mph) and at times receding at the same speed. This regular pattern repeats with a period of 11.2 days. Careful analyses of the resulting tiny Doppler shifts in this case indicate the presence of a planet with a mass at least 1.3 times that of the Earth.

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. Dr Barnes 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.”

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

Speaking on the possibility of life being found on the planet, Dr Mikko Tuomi from the University of Hertfordshire, 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. But we do not really know. 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.’

This discovery will be the beginning of extensive further observations, both with current instruments and with the next generation of giant telescopes such as ESO’s European Extremely Large Telescope (E-ELT) in which the UK government has invested £88 million. Proxima b will be a prime target for the hunt for evidence of life elsewhere in the Universe.

Video courtesy of STFC.

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