They inhabit billions of tiny planets that exist within the Milky Way.

These “super-Earths” less than 30 light years, or about 180 trillion miles from the sun, were discovered while astronomers were surveying red dwarf stars, which account for about four in five stars in the galaxy.

The researchers found that 40 per cent of these red dwarf stars have a rocky planet, slightly larger than Earth, orbiting the “habitable zone” in which liquid surface water can exist – and where there is water, there can be life.

Dr Xavier Bonfils, from Grenoble University in France, who led the international team using the European Southern Observatory’s 3.6-metre telescope at La Silla, Chile, said: ”Because red dwarfs are so common – there are about 160 billion of them in the Milky

Way – this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone.”

However, Red dwarfs are cooler than the sun, which means planets must orbit close to their parent stars to be warm enough to be habitable. Scientists said this might not be good news for life.

Picture: NASA