Rocky, Earth-like planets with high levels of radiation, orbiting our closest stars could be hosting life, suggests a new study raising excitement about exoplanets. Previously, the discovery of fierce radiation had dashed hopes that nearby exoplanets may have life.
But, astronomers at Cornell University in the US found that all of life on Earth evolved from creatures that thrived during an even greater ultraviolet radiation assault than nearby exoplanets like Proxima-b which receives 250 times more X-ray radiation than Earth.
The Earth 4 billion years ago was a chaotic, irradiated, hot mess, not unlike what is happening on some of the nearest exoplanets. Yet in spite of this, life somehow gained a toehold and then expanded, the study revealed.
The same thing could be happening at this very moment on some of the nearest exoplanets, according to the researchers including Lisa Kaltenegger, Associate Professor at Cornell University.
For the study, published in the Monthly Notices of the Royal Astronomical Society journal, the team modelled the surface ultraviolet environments of the four exoplanets closest to Earth – Proxima-b, TRAPPIST-1e, Ross-128b and LHS-1140b – and are potentially habitable.
Those planets orbit small red dwarf stars which, unlike our sun, flare frequently, bathing their planets in high-energy radiation. The researchers compared the models to Earth's history, from nearly 4 billion years ago to today.
High levels of radiation cause biological molecules like nucleic acids to mutate or even shut down. Although modelled planets receive higher ultraviolet radiation than that emitted by our own sun today, it is significantly lower than what Earth received 3.9 billion years ago.
"Given that the early Earth was inhabited, we show that ultraviolet radiation should not be a limiting factor for the habitability of planets orbiting M stars. Our closest neighbouring worlds remain intriguing targets for the search for life beyond our solar system," the researchers said.
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