Life on Earth-like planets could be impeded by global warming, scientists say
Global warming may get in the way of life on billions of Earth-like planets orbiting the most common stars in our galaxy, the Milky Way, say scientists.
But there could still be a "bonanza" of small habitable worlds the size of Mars, experts believe.
Earth-sized planets orbiting close to dim red dwarf stars were initially thought to be good candidates for the emergence of life.
The new research suggests that even though these "habitable zone" worlds may be the right distance from their stars to permit liquid surface water, they are likely to be encased in stifling atmospheres.
Their thick atmospheres would cause a runaway greenhouse effect, boiling away water and rendering them too hot for life. A similar effect is seen on Venus, where surface temperatures are hot enough to melt lead.
Since red dwarfs make up around three-quarters of the stars in the Milky Way, scientists had expected them to host billions of habitable planets.
Although many of these planets are born with thick hydrogen and helium atmospheres, radiation from the parent stars was expected to blast away much of the gas.
Detailed computer simulations have now shown that planets the size of Earth or larger orbiting close to red dwarfs are likely to retain their thick atmospheres.
On the other hand, smaller planets similar in size to Mars might lose enough of their atmospheres to make them habitable.
Dr Subhanjoy Mohanty, one of the researchers from Imperial College London, said: "There are hints from recent exoplanet discoveries that relatively puny planets may be even more common around red dwarfs than Earth mass or larger ones, in which case there may indeed be a bonanza of potentially habitable planets whirling around these cool red stars."
The study is published in the journal Monthly Notices of the Royal Astronomical Society.