The three planets are smaller than Earth and appear to be rocky with a solid surface, the team of astronomers, led by scientists at the California Institute of Technology, says.
Until now, astronomers have found at most only four other rocky planets, also called terrestrial planets, around other stars, a Caltech release said Wednesday.
While the new planets are too close to the star to be in its habitable zone -- the narrow region around a star where the temperature is mild enough for liquid water, and possibly life, to exist -- the planets are the first rocky ones to be found orbiting a type of dim, small star called a red dwarf, the most common type of star in the Milky Way.
That suggests our galaxy could be teeming with similarly rocky planets, with the possibility that many are in the habitable zone, astronomers said.
"Red dwarfs make up eight out of every ten stars in the galaxy," Caltech astronomy Professor John Johnson said. "That boosts the chances of other life being in the universe -- that's the ultimate result here."