A new study suggests that the Earth could be just one of 800 billion planets.
Scientists writing in the journal Nature say the 700 planets discovered so far, are only a tiny fraction of those that exist.
Since 2009, the Kepler Space Observatory has repeatedly photographed the stars in a narrow patch of space between the constellations Cygnus and Lyra.
A team, led by Arnaud Cassan at the Institute of Astrophysics in Paris, now concludes that planets may be commonplace.
The BBC's Science Correspondent reports they found that more than half the stars in the night sky had a planet in orbit.