Extrapolating from these findings, the researchers estimate that tens of billions of these planets are to be found in the Milky Way, and about 100 should lie in the immediate neighborhood of the sun. [Vote Now! Strangest Alien Planet Finds]
"Our new observations with HARPS mean that about 40 percent of all red dwarf stars have a super-Earth orbiting in the habitable zone where liquid water can exist on the surface of the planet," team leader Xavier Bonfils of the Observatoire des Sciences de l'Univers de Grenoble in France said in a statement. "Because red dwarfs are so common — there are about 160 billion of them in the Milky Way — this leads us to the astonishing result that there are tens of billions of these planets in our galaxy alone."
The two stars found inside the habitable zone were discovered around the stars Gliese 581 and Gliese 667 C. The latter planet is the second of three worlds orbiting its star, and seems to lie right in the middle of Gliese 667 C's habitable zone. Although the planet has four times the mass of Earth, it is considered the closest twin to Earth found so far.
This and other planets are good candidates for follow-up studies that aim to analyze the atmospheres of these worlds for signs that organisms are living there.
"Now that we know that there are many super-Earths around nearby red dwarfs, we need to identify more of them using both HARPS and future instruments," said team member Xavier Delfosse. "Some of these planets are expected to pass in front of their parent star as they orbit — this will open up the exciting possibility of studying the planet's atmosphere and searching for signs of life."