A newly discovered planet orbiting a nearby star could be the closest world to Earth offering life a comfortable home.
The Earth-sized planet, named Ross 128b, is just 11 light years away and thought to have a “mild” climate with temperatures ranging between an icy minus 60C and balmy 20C.
That could mean it has oceans and lakes in which life may have evolved.
But the best news for any plants or animals living on Ross 128b is the planet’s peaceful parent star.
Like many other exoplanets, it orbits close to a dim and cool “red dwarf” at a distance 20 times less than that between the sun and Earth.
Red dwarfs have tightly bound “habitable zones” – the narrow temperature belts where surface water can exist as a liquid – but are also prone to deadly eruptions of ultraviolet radiation and X-rays.
Habitable zone planets around most red dwarfs are likely to be severely irradiated, causing many scientists to doubt that life could survive on them.
Stars blaze above the European Southern Observatory’s 3.6 metre telescope at La Silla, Chile (ESO/B. Tafreshi/twanight.org)
However, Ross 128b’s star is much less volatile than typical red dwarfs. The planet’s surface receives only 1.38 times more radiation than the Earth, scientists believe.
Conditions on what is technically the closest habitable zone exoplanet to Earth, Proxima Centauri b, are likely to be far less pleasant.
Its parent Proxima Centauri is also a red dwarf and part of the Alpha Centauri triple star system, just over four light years from Earth.
The star unleashes bursts of radiation and “solar wind” particles powerful enough to strip the atmosphere from a nearby planet.
Astronomer Dr Xavier Bonfils, from the University of Grenoble, France, who led the European team behind the new discovery, said: “Many red dwarf stars, including Proxima Centauri, are subject to flares that occasionally bathe their orbiting planets in deadly ultraviolet and X-ray radiation.
“However, it seems that Ross 128 is a much quieter star, and so its planets may be the closest known comfortable abode for possible life.”
Ross 128b was spotted by a highly successful planet-finding instrument attached to the European Southern Observatory’s 3.6-metre telescope at La Silla, Chile.
The High Accuracy Radial Velocity Planet Searcher (Harps) looks for tiny wobbles in a star’s motion caused by its gravitational interaction with planets orbiting it.
The “tug-of-war” between star and planet is revealed in shifts in the wavelengths of light emitted by the star. From these readings, astronomers can make calculations about a planet’s mass and orbit.
While Ross 128b is considered to be a “temperate” planet, astronomers are still not certain where it lies in relation to its star’s habitable zone.
Proxima b – the closest habitable zone exoplanet to Earth – is likely to be blasted by radiation from its parent star, making it hostile to life (Artist’s impression/ESO/M Kornmesser)
Within the next 10 years, a new generation of ultra-powerful telescopes will start studying the atmospheres of exoplanets looking for signs of life, such as oxygen.
They include the ESO’s 39-metre Extremely Large Telescope under construction in Chile which is due to begin operating in 2024.
The research is to appear in the journal Astronomy & Astrophysics.