Is there anybody out there?: An artist's impression of an Earth-like alien world bombarded with meteorites.
Credit: NASA
Bigger and better: NASA's terrestrial planet finder has the right equipment, but just isn't big enough.
Credit: NASA
SYDNEY: Large space telescopes could zoom in on the atmospheres of planets around other stars, helping to speed up the search for extraterrestrial life, says a new study.
A new space-based telescope costing about A$12.3 billion (US$10 billion) could detect alien life on extrasolar planets using technology already available today, said Steve Beckwith, author of the report and astronomer at the University of California, Berkeley.
He said that methods, such as observing the change in light from a star as a planet passes in front, or blocking the light from stars and focussing on the faint light of their planets instead, could reveal tell-tale traces of oxygen, carbon dioxide, methane and water vapour in the planets’ atmospheres. These could then be analysed for clues to alien life.
A price worth paying?
Though over 300 extrasolar planets have been found to date, only one has been found within the habitable zone of its star (see, New Earth-like planet may hold liquid water, Cosmos Online). This zone is the favourable region of space around a star that is though to have encouraged life on Earth.
Beckwith’s research, published this week in the Astrophysical Journal, calculates the technical requirements needed to detect the chemical signatures of life in the light spectrum of Earth-like planets when viewed from across the galaxy.
One of the most useful techniques for this sort of search is coronagraphy, said Beckwith. Coronagraphs were originally invented to study the Sun's corona (its atmosphere), but they are also capable of blocking the light from bright stars to allow us to observe their planets more clearly.
However, projects currently in the pipeline to observe extrasolar planets, such as NASA’s Terrestrial Planet Finder’s coronagraph, due for launch in 2014, don’t have sufficiently large apertures, he said. The consequence being that planets of interest might end up spending the majority of their time behind the part of the instrument used to block the light of the star, he said.
To spot life-bearing planets effectively, there is a need for larger, space-based telescopes with diameters of eight to ten metres, said Beckwith, the downside being the great expense. “But considering the amount we routinely spend on other sectors of the government and the excitement that would result from the first discovery of extra-terrestrial life, it is a sum that society may well want to spend,” he told Cosmos Online.
Seeking out life
The difficulty in searching for life on extrasolar planets is the incredibly dim light from the planets themselves coupled with their proximity to very bright stars.
“It takes a powerful telescope just to detect the light from the exoplanets directly… [and] then it is extraordinarily difficult to block the light from the nearby star so it does not interfere with the observations,” Beckwith said. He likened the challenge to "trying to see a mosquito, sitting on the edge of a powerful searchlight, viewed from ten kilometres away".
But the advantage of this kind of search is that it doesn't limit us to looking for intelligent aliens, said Beckwith, who believes we're more likely to find microbial- than sentient life in space
Commenting on the research, Charley Lineweaver, an astrophysicist with the Australian National University, in Canberra, said it was a “very nice contribution to efforts to detect extraterrestrial life."
”If we invest in building such a telescope, we could know whether we really are alone in the universe within our lifetimes,” he said. “Most scientists subscribe to the idea life in the universe is probably more common than intelligent life. This sort of survey is more legitimate than [projects searching for alien radio signals, such as] SETI because of this”.
Lineweaver added that the existence of alien life is one of the most compelling questions that astronomy can answer. “For some reason people still think this is a wild and crazy idea but that’s not the case. This is something we could achieve within five to ten years,” he said.
