A quiet star could let life flourish here ESO/M. Kornmesser

A newly discovered planet orbiting a nearby star could be the closest world to Earth that offers a comfortable home for life. The Earth-sized planet, named Ross 128b, is just 11 light years away and thought to have a relatively mild climate with temperatures ranging between an icy -60°C and balmy 20°C.

That could mean it has oceans and lakes in which life may have evolved. But the best news for possible life on Ross 128b is the planet’s peaceful parent star. Like many other exoplanets that we’ve found, it orbits close to a dim and cool red dwarf star at a distance 20 times less than that between the sun and Earth.

The habitable zone of a red dwarf – the narrow temperature belts where surface water can persist without freezing or boiling away – is usually quite close to the star. Since red dwarfs are prone to deadly eruptions of ultraviolet radiation and X-rays, this can be dangerous. Planets close to most red dwarfs are likely to be severely irradiated, causing many scientists to doubt that life could survive on them regardless of whether they’re in the habitable zone.


However, Ross 128b’s star is much less volatile than typical red dwarfs. Even though the planet orbits quite near its star, its surface probably receives only about 1.38 times more radiation than the Earth.

Wobbly star motion

Conditions on the closest exoplanet to Earth that sits in a habitable zone, Proxima Centauri b, are likely to be far less pleasant. Its star, Proxima Centauri, is also a red dwarf, but it regularly unleashes bursts of radiation and solar wind particles powerful enough to strip the atmosphere from a nearby planet.

Compared to Proxima Centauri and many other red dwarfs, “it seems that Ross 128 is a much quieter star, and so its planets may be the closest known comfortable abode for possible life,” said Xavier Bonfils at the University of Grenoble, France, who led the European team behind the new discovery. Their work will soon be published in the journal Astronomy & Astrophysics.

Not only is Ross 128b potentially better for life than Proxima Centauri b, it is also moving toward Earth. The team says that in about 79,000 years Ross 128 will be our nearest stellar neighbor, making Ross 128b the nearest exoplanet.

Ross 128b was spotted by a planet-finding instrument attached to the European Southern Observatory’s 3.6-metre telescope in La Silla, Chile. The High Accuracy Radial Velocity Planet Searcher (HARPS) looks for tiny wobbles in a star’s motion caused by the gravitational tug-of-war between the star and its planets. 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. Since the planet does not pass between its star and Earth, it’s difficult for us to study it in more detail and find out.

It could be an oasis for life. Or it could be a sweltering hellscape more like Venus, or a frozen wasteland like Neptune with no possibility of liquid water.

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