Astronomers discovered three so-called "super-Earths" orbiting the star HD 40307:
The new worlds, which circle the star HD 40307, are 4.2, 6.7 and 9.4 times the size of Earth. They are named super-Earths because they are more massive than the Earth but less massive than Uranus and Neptune (which are about 15 Earth masses).
Using Harps data, the astronomers also counted a total of 45 candidate planets with a mass below 30 Earth masses.
This implies that one solar-like star out of three harbours such planets.
Astronomer Michel Mayor from the Geneva Observatory in Switzerland commented: "Does every single star harbour planets and, if yes, how many?
"We may not yet know the answer but we are making huge progress towards it."
Since the discovery in 1995 of a planet around the star 51 Pegasi by Michel Mayor and his colleague Didier Queloz, more than 270 exoplanets have been found - mostly around Sun-like stars.
The majority of these planets are gas giants, a bit like Jupiter or Saturn in our own Solar System. Current data shows that about one in 14 stars harbours this kind of planet.