Nasa has discovered new evidence that Earth-like planets are common in the galaxy – boosting the chances that we have alien neighbours. The Spitzer space telescope has shown that up to 60 per cent of nearby stars like the sun are likely to have rocky worlds in orbit around them.

The findings, announced at a conference in Boston today, are a major boost to the chances that extra-terrestrials exist throughout the universe.

Astronomer Michael Meyer, of the University of Arizona, and colleagues used Spitzer to survey six sets of stars similar in mass to the sun, in different age groups.

Meyer said: “We wanted to study the evolution of the gas and dust around stars similar to the sun and compare the results with what we think the solar system looked like at earlier stages during its evolution.”

The Spitzer telescope is heat-seeking – it observes with infrared eyes – and is able to detect dust left from the collisions as planets form. They found warm dust around up to a fifth of stars in the four younger age bands.

Meyer said: “That’s comparable to the time scales thought to span the formation and dynamical evolution of our own solar system.”

In a separate study, Thayne Currie and Scott Kenyon, of the Smithsonian Astrophysical Observatory, Cambridge, Massachusetts, and their colleagues also found evidence of dust from terrestrial planet formation around stars from 10 to 30 million years old. “These observations suggest that whatever led to the formation of Earth could be occurring around many stars between three million and 300 million years old,” Meyer said.

He said interpretation of the data showed that at least one star in five like the sun is potentially forming new worlds, but that as many as 62 per cent of the stars studied could have their own families of planets.

“The correct answer probably lies somewhere between the pessimistic case of less than 20 per cent and optimistic case of more than 60 per cent,” Meyer said.

Last year we reported how a planet had been found in the so-called Goldilocks Zone where a world might support life as we know it. And the discovery of an individual solar system, said to be similar to our own, was announced last week.

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