Scientists have proposed a new method for finding Earth-like planets in our Milky Way galaxy and they anticipate that their number may be up to a whopping 100 billion.
The strategy devised by researchers at The University of Auckland uses a technique called gravitational microlensing, currently used by a Japan-New Zealand collaboration called MOA (Microlensing Observations in Astrophysics) at New Zealand's Mt John Observatory.
Lead author Dr Phil Yock from the University of Auckland's Department of Physics said that the work will require a combination of data from microlensing and the NASA Kepler space telescope.
"Kepler finds Earth-sized planets that are quite close to parent stars, and it estimates that there are 17 billion such planets in the Milky Way. These planets are generally hotter than Earth, although some could be of a similar temperature (and therefore habitable) if they're orbiting a cool star called a red dwarf," Yock said.
"Our proposal is to measure the number of Earth-mass planets orbiting stars at distances typically twice the Sun-Earth distance. Our planets will therefore be cooler than the Earth.
"By interpolating between the Kepler and MOA results, we should get a good estimate of the number of Earth-like, habitable planets in the Galaxy. We anticipate a number in the order of 100 billion.
"Of course, it will be a long way from measuring this number to actually finding inhabited planets, but it will be a step along the way," Yock said in a Royal Astronomical Society (RAS) statement.
While Kepler measures the loss of light from a star when a planet orbits between us and the star, microlensing measures the deflection of light from a distant star that passes through a planetary system en route to Earth - an effect predicted by Einstein in 1936.
In recent years, microlensing has been used to detect several planets as large as Neptune and Jupiter.
Yock and colleagues have proposed a new microlensing strategy for detecting the tiny deflection caused by an Earth-sized planet.
Simulations carried out by Yock and his colleagues - students and former students from The University of Auckland and France - showed that Earth-sized planets could be detected more easily if a worldwide network of moderate-sized, robotic telescopes was available to monitor them.
Coincidentally, just such a network of telescopes is now being deployed by Las Cumbres Observatory Global Telescope Network (LCOGT) in collaboration with SUPA/St Andrews (Scottish Universities Physics Alliance), with three telescopes in Chile, three in South Africa, three in Australia, and one each in Hawaii and Texas.
The study will appear in the journal Monthly Notices of the Royal Astronomical Society.
