A whopping 100 billion planets may be like Earth in our Milky Way Galaxy?

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.

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