Earth-like planets may have formed around most of the Milky Way’s Sun-like stars, according to research that shortens the odds on the discovery of extra-terrestrial life.

Observations using Nasa’s Spitzer Space Telescope have found that at least 20 per cent — and perhaps as many as 60 per cent — of our galaxy’s Sun-like stars are good candidates for having rocky planets of the sort that can harbour life.

The findings offer further evidence suggesting that such worlds may be common in the galaxy, which would greatly enhance the prospects for finding one on which life has developed.

Last week another team of astronomers announced the discovery of a star system about 5,000 light years from Earth that looks like a “scale model” of our own Solar System.

In the Nasa research, which was presented at the American Association for the Advancement of Science conference in Boston, a team led by Michael Meyer, of the University of Arizona, used the Spitzer telescope to survey six groups of stars with masses similar to the Sun’s.

The Spitzer can detect and measure the temperature of dust clouds around stars from which planets can form. The stars surveyed were grouped according to their age — the youngest are between 3 million and 10 million years old, while the oldest are between 1 billion and 3 billion years old. The Sun is about 4.6 billion years old.

Dr Meyer said the results, which are published in Astrophysical Journal Letters, matched theories about how the Earth formed. “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,” he said. “Theoretical models and meteoritic data suggest the Earth formed over 10 to 50 million years from collisions between smaller bodies.”

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