In a project funded by NASA and the University of California, the W.M. Keck Observatory atop Mauna Kea in Hawaii, was used to survey 166 sun-like stars for planets of different sizes, a NASA release said Thursday.
The survey found more small planets than large ones, suggesting they are more prevalent in our Milky Way galaxy, NASA said.
"We studied planets of many masses -- like counting boulders, rocks and pebbles in a canyon -- and found more rocks than boulders, and more pebbles than rocks," Andrew Howard of the University of California, Berkeley, said.
"Our ground-based technology can't see the grains of sand, the Earth-size planets, but we can estimate their numbers," he said.
"Earth-size planets in our galaxy are like grains of sand sprinkled on a beach -- they are everywhere."
The study has been published in the journal Science.