PARIS • An international team of scientists say they have discovered a trio of Earth-like planets that are the best bet so far for finding life outside our solar system.
The planets orbit an ultra-cool dwarf star 39 light years away, and are likely comparable in size and temperature to Earth and Venus, reported the study published in the journal Nature on Monday.
"This is the first opportunity to find chemical traces of life outside our solar system," said lead author Michael Gillon, an astrophysicist at the University of Liege in Belgium.
All three planets had the "winning combination" of being similar in size to Earth, "potentially habitable" and close enough so their atmospheres can be analysed with current technology, he said. The find opens up a new "hunting ground" for habitable planets.
Mr Gillon and colleagues calibrated a 60cm robotic telescope in Chile to track several dozen dwarf stars that are not big or hot enough to be visible with optical telescopes. They zeroed in on a particularly promising one about one- eighth the size of the Sun, and significantly cooler.
Observing it for months, the astronomers noticed that its infrared signal faded slightly at regular intervals - evidence of objects in orbit. Analysis confirmed the objects were exoplanets - planets revolving around stars outside our solar system. Co-author Emmanuel Jehin, also from the University of Liege, called the discovery a "paradigm shift" in the search for life in the universe.
Given their size and proximity to their low-intensity star, all three planets may have regions at temperatures suitable for sustaining liquid water and life, the study said.
Co-author Julien de Wit from the Massachusetts Institute of Technology said it should be possible to determine if the planets harbour life "within our generation".