The hunt for exo-planets has been going on ever since their was confirmation that there were other solar systems and galaxies out side ours. Astronomy has evolved from just some guy looking out through his telescope out in to the cosmos to giant telescopes floating around in space as part of a $300 billion industry.
Since the search, 1800 extra-solar planets have been discovered and a small number have been assumed to be habitable (meaning that they are estimated to be in the habitable zone in a solar system which is not too close or too far away from their star so that liquid water maybe present on the planet). One of these was announced by NASA on April 17th 2014, called Kepler 186f (for the star it orbits called Kepler 186).
Kepler 186f is 490 light years away from Earth and orbits a dwarf star. Kepler 186f is 50% heavier than earth and is 10% bigger, so it almost definitely has an atmosphere if nothing catastrophic has occurred to prove otherwise but that does not mean that Kepler 186f is a habitable planet.
Its on the edge of the habitable zone in its solar system and due to its relative closeness to Earth it maybe a viable option to travel to if our planet is somehow rendered inhabitable. The problem is that there are other factors that determine a planets habitability. Mars is in the habitable zone in our solar system and as far as we know, it never harboured life, though it most certainly once had water.
As more data comes in we’ll have to wait and see whether Kepler 186f meets our expectations as a habitable planet.