Scientists will have detected the first truly Earth-like planet outside the solar system by the end of the year, one of the world’s leading astronomers predicted yesterday.
Professor Michel Mayor, of Geneva University, who led the team that discovered the first extrasolar planet (or exoplanet) in 1995, said he was confident that a planet of a similar size and composition to Earth would be found in the near future.
Addressing a Royal Society conference to mark the 50th anniversary of the Search for Extra-Terrestrial Intelligence (SETI) programme, he said: “The search for twins of Earth is motivated by the ultimate prospect of finding sites with favourable conditions for the development of life. We’ve entered a new phase in this search.”
He told the audience, which included representatives from Nasa, the European Space Agency and the UN Office for Outer Space Affairs, that dramatic technological progress over the past 15 years had led to the discovery of more than 400 exoplanets orbiting stars similar to the Sun.
However, very few if any of the the planets discovered so far are likely to be viable candidates for incubating life, as most of them are too large. Very large planets are likely to have very active tectonic plates, making for a highly turbulent environment. To date, the smallest exoplanet found is 1.7 times the mass of the Earth.
A further condition for a planet to be habitable is that it orbits its star at such a distance that its water would be liquid. “If the planet’s too close, it will be blazing hot and all the water will evaporate and if it’s too far away, it will be ice,” Professor Mayor said.
He said that Nasa’s Kepler spacecraft, which is carrying the largest telescope to have been sent beyond the Earth’s orbit, will be the first to find a planet that meets both these criteria. The telescope, which has been in orbit around the Sun since March last year, is focused on a dense star field in the Orion spiral arm of the Milky Way. Monitoring more than 100,000 stars every half-hour for three years, it is looking for variations in the brightness of stars caused by planets as small as Earth passing in front of them.
Within about four years Kepler is likely to have found planets of the same size as Earth that are also in the “habitable zone”.
Professor Paul Davies, an astrophysicist at Arizona State University, also spoke. “When I was a student, I couldn’t find anyone who took the idea of life elsewhere in the Universe seriously. Now it’s pretty much the party line in the scientific community. A big part of that has been the discovery of extrasolar planets,” he said.