By scouring millions of stars in the night sky over six years, researchers found that the majority of the 100 billion stars in the Milky Way have planets similar to Earth or Mercury, Venus or Mars, the other similar planets in our solar system.
They estimated that in our galaxy there are about 10 billion stars with planets in the "habitable zone" – the distance from the star where solid planets can be found – many of which could in theory be capable of supporting life.
Dr Martin Dominik, a German research fellow at St Andrews University, said: "Even if life existed on only one planet in each galaxy there would still be 100 billion in the universe.
"We still don't have the evidence of life on another planet, and we could be unique, but confronted with these numbers it seems highly unlikely.
"There are a small number of planets which we think could harbour life, a small number of candidates with what we believe might be the right conditions."
More than 1,000 planets have already been detected in our galaxy, but the two different methods used to find them are best suited to those which are large and close to their host star – unlike anything in our solar system.
Using a third technique known as gravitational microlensing, the international team of astronomers were able to confirm the existence of planets at a similar distance from their star as Earth without directly seeing them.
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