Life could not survive on nearest Earth-like planet, scientists believe
Hopes of finding life on our nearest Earth-like planet have been dashed after scientists revealed it is being bombarded with radiation.
The rocky planet - which orbits our closest star, Proxima Centauri - has been a source of considerable interest for scientists who thought it had the right conditions to harbour life.
In astronomical terms, the planet known as Proxima b is just next door to our solar system at a distance slightly exceeding four light years, or 25 trillion miles.
Research had previously suggested Proxima b is in the “habitable zone” of the star it orbits, where temperatures were mild enough for water to remain a liquid.
Now, however, scientists face having to go further afield in their search for life beyond our solar system after it emerged the planet was inhospitable.
A new analysis of solar radio bursts and stella flares surrounding Proxima Centauri, which is a red dwarf, found that Proxima b lies too close to it and subsequently endures punishing space weather.
Despite being closer to Proxima Centauri than Mercury is to the Sun, scientists believe Proxima b is in the habitable zone where it receives similar amounts of heat and light to Earth because the red dwarf is small and has a significantly cooler temperature.
It was hoped when Proxima b was discovered four years ago that the planet would be able to enjoy a climate as benign as Earth.
However, Dr Andrew Zic, the lead author of the latest study, published in the Astrophysical Journal, said: "What our research shows is this makes the planets very vulnerable to dangerous ionising radiation that could effectively sterilise them."
This problem does not plague life on Earth in the same way because the hot clouds of ionised particles emitted by the Sun are too far away and our planet is shielded by a powerful planetary magnetic field.
Dr Zic, of Macquarie University, Sydney, added: "This is probably bad news on the space weather front.
"It seems likely the galaxy's most common stars - red dwarfs - won't be great places to find life as we know it."
The second-closest exoplanet which scientists believe could harbour life is known as Barnard’s Star b, as it orbits Barnard’s Star, six light years away.
There are now more than 4,000 known exoplanets which revolve around stars beyond our solar system.
Proxima b is around 4.7 million miles from its star and takes around 11 days to complete an orbit, compared to the 365 days it takes the Earth to orbit the Sun, which is 93 million miles away.
The latest findings about Proxima b were based on observational data from space and land-based telescopes that captured the space conditions in “amazing detail”.
It suggests that planets around red dwarfs such as Proxima Centauri are likely to be showered with stellar flares and plasma ejections.
The orbiting planets would therefore suffer from strong “atmospheric erosion”, which would expose them to very intense ultraviolet radiation.
Co-author Dr Bruce Gendre, of Western Australia University, said: "Understanding space weather is critical for understanding how our own planet biosphere evolved - but also for what the future is."
Magnetic fields like Earth's have never been identified around an exoplanet - and finding them could prove tricky.
Dr Zic said: "Even if there were magnetic fields, given the stellar proximity of habitable zone planets around red dwarf stars, this might not be enough to protect them."
