A telescope to find rocky worlds around other stars has been selected for launch by the European Space Agency's (ESA) Science Policy Committee.
Known as Plato, the mission should launch on a Soyuz rocket in 2024.
The observatory concept was chosen following several years of assessment in competition with other ideas.
It is expected to cost ESA just over 600 million euros, although hardware contributions from member states will take this closer to a billion (£800m [$822 Million -me]).
Astronomers have so far found over 1,000 planets beyond our Solar System, but none as yet has been shown to be truly Earth-like in terms of its size and distance from a Sun similar to our own.
The PLAnetary Transits and Oscillations of stars mission will look to change that.