Scientists offer tips in search for aliens
Theory may increase odds of finding life in space
By Julian Lee While many people may think the chances of finding life elsewhere in the universe as good as finding a needle in a haystack, research by three ANU astrophysicists may just increase those odds. Doctors Jianke Li, Lilia Ferrario and Professor Dayal Wick-ramasinghe of the Astrophysical Theory Centre in the School of Mathematical Sciences have developed a theory which could be used to detect planets the mass of the Earth around a star the size of the Sun - the only situation where life is known to exist. The team of astrophysicists believe that the emission of polarised light from a white dwarf star in the constellation Draco - 65 light years away - could be explained by the existence of an Earth-type planet, too small to be detected using current technology, orbiting the collapsed star. "This theory is the first viable explanation for unusual emissions coming from this white dwarf," Prof Wickramasinghe said. Unlike larger stars which explode in dramatic supernova, small stars like the Sun "gently" expand, consuming planets closest to the star, removing the atmosphere and crust of planets further away, while leaving the most distant intact. Eventually the star collapses to form a white dwarf around which the metal cores of surviving inner planets orbit. "The metallic core of a planet moving through the strong magnetic field of a white dwarf acts like a giant generator and produces an electric current. This electricity excites hydrogen atoms at the poles of the star which would then emit light polarised by the magnetic field," Dr Ferrario said. If true, then finding Earth-type planets would be a relatively simple matter of detecting white dwarfs which emit polarised light, she said. "The implication of this theory is that not only can we detect planets that would have been similar in mass to the Earth, we can detect them around stars that would have been about the mass of the Sun," Dr Ferrario said. Stars much more massive than the Sun burn faster and explode before life has a chance to develop. On the other hand the Sun, which has a relatively low mass and is not due to collapse to a white dwarf for another few billion years, has allowed plenty of time for life to evolve, Dr Ferrario said. Prof Wickramasinghe believes that a case could be made for extending the Search for Extra-Terrestrial Intelligence (SETI) program to include white dwarfs where life as we know it may have once developed and flourished. "While any technologically advanced civilisations would have left their endangered planet a long time ago, they may well have colonised other nearby planets and be sending out signals to the rest of the universe," Prof Wickramasinghe said.