It has also detected nine small planets within the so-called habitable zone, where conditions are favourable for liquid water - and potentially life.The finds are contained within a catalogue of 1,284 new planets detected by Kepler - which more than doubles the previous tally. Nasa said it was the biggest single announcement of new exoplanets. Space agency scientists discussed the new findings in a teleconference on Tuesday.
Statistical analyses of the expanding sample of worlds helps astronomers understand how common planets like our own might be.
Dr Natalie Batalha, Kepler mission scientist at Nasa's Ames Research Center in California, said the calculations so far suggested there could be tens of billions of potentially habitable planets in the Milky Way.
"If you ask yourself where is the next habitable planet likely to be, it's within about 11 light-years, which is very close," said Dr Batalha.
Astronomers said they consider planets that are 1.6 times Earth's radius or smaller are likely to be rocky, and may therefore be potential targets in the hunt for life.
Future telescopes such as the James Webb Space Telescope could analyse the light from the atmospheres of exoplanets for potential markers of biology.
Dr Batalha said the Kepler mission was part of a "larger strategic goal of finding evidence of life beyond Earth - knowing whether we're alone or not, to know... how life manifests itself in the galaxy and what is the diversity".
She added: "Being able to look up to a point of light and being able to say: 'That star has a living world orbiting it.' I think that's very profound and answers questions about why we're here." Read more