* Astronomy

A proposed space mission could find hundreds of free-floating, Earth-size planets that were ejected from their solar systems in primordial tussles with their siblings. Based on a technique called microlensing, the mission could also find many planets orbiting their parent stars at the right distance to support life.
Astronomers have discovered more than 200 planets orbiting other stars. But the main technique used so far, which finds planets by the wobble they induce in their parent stars, is not sensitive enough to find planets as small as Earth.
One technique that has the required sensitivity to detect Earth-like planets is called microlensing. Using the technique, ground-based telescopes have so far detected four planets, each much more massive than Earth.
The technique takes advantage of the fact that a massive object's gravity can act like a lens, bending light rays that pass nearby. A background star can appear to brighten if an object such as a star passes between it and Earth, and if the intervening star hosts a planet, the planet can produce a second, smaller spike in brightness.

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